This article was originally featured on The Conversation.

Spring, summer, fall and winter–the seasons on Earth change every few months, around the same time every year. It’s easy to take this cycle for granted here on Earth, but not every planet has a regular change in seasons. So why does Earth have regular seasons when other planets don’t?

I’m an astrophysicist who studies the movement of planets and the causes of seasons. Throughout my research, I’ve found that Earth’s regular pattern of seasons is unique. The rotational axis that Earth spins on, along the North and South poles, isn’t quite aligned with the vertical axis perpendicular to Earth’s orbit around the Sun.

That slight tilt has big implications for everything from seasons to glacier cycles. The magnitude of that tilt can even determine whether a planet is habitable to life.

Seasons on Earth

When a planet has perfect alignment between the axis it orbits on and the rotational axis, the amount of sunlight it receives is fixed as it orbits around the Sun–assuming its orbital shape is a circle. Since seasons come from variations in how much sunlight reaches the planet’s surface, a planet that’s perfectly aligned wouldn’t have seasons. But Earth isn’t perfectly aligned on its axis.

This small misalignment, called an obliquity, is around 23 degrees from vertical for Earth. So, the Northern Hemisphere experiences more intense sunlight during the summer, when the Sun is positioned more directly above the Northern Hemisphere.

Then, as the Earth continues to orbit around the Sun, the amount of sunlight the Northern Hemisphere receives gradually decreases as the Northern Hemisphere tilts away from the Sun. This causes winter.

The planets spinning on their axes and orbiting around the Sun look kind of like spinning tops–they spin around and wobble because of gravitational pull from the Sun. As a top spins, you might notice that it doesn’t just stay perfectly upright and stationary. Instead, it may start to tilt or wobble slightly. This tilt is what astrophysicists call spin precession.

Because of these wobbles, Earth’s obliquity isn’t perfectly fixed. These small variations in tilt can have big effects on the Earth’s climate when combined with small changes to Earth’s orbit shape.

The wobbling tilt and any natural variations to the shape of Earth’s orbit can change the amount and distribution of sunlight reaching Earth. These small changes contribute to the planet’s larger temperature shifts over thousands to hundreds of thousands of years. This can, in turn, drive ice ages and periods of warmth.

Translating obliquity into seasons

So how do obliquity variations affect the seasons on a planet? Low obliquity, meaning the rotational spin axis is aligned with the planet’s orientation as it orbits around the Sun, leads to stronger sunlight on the equator and low sunlight near the pole, like on Earth.

On the other hand, a high obliquity–meaning the planet’s rotational spin axis points toward or away from the Sun–leads to extremely hot or cold poles. At the same time, the equator gets cold, as the Sun does not shine above the equator all year round. This leads to drastically varying seasons at high latitudes and low temperatures at the equator.

When a planet has an obliquity of more than 54 degrees, that planet’s equator grows icy and the pole becomes warm. This is called a reversed zonation, and it’s the opposite of what Earth has.

Basically, if an obliquity has large and unpredictable variations, the seasonal variations on the planet become wild and hard to predict. A dramatic, large obliquity variation can turn the whole planet into a snowball, where it’s all covered by ice.

Spin orbit resonances

Most planets are not the only planets in their solar systems. Their planetary siblings can disturb each other’s orbit, which can lead to variations in the shape of their orbits and their orbital tilt.

So, planets in orbit look kind of like tops spinning on the roof of a car that’s bumping down the road, where the car represents the orbital plane. When the rate–or frequency, as scientists call it–at which the tops are precessing, or spinning, matches the frequency at which the car is bumping up and down, something called a spin-orbit resonance occurs.

Spin-orbit resonances can cause these obliquity variations, which is when a planet wobbles on its axis. Think about pushing a kid on a swing. When you push at just the right time–or at the resonant frequency–they’ll swing higher and higher.

Mars wobbles more on its axis than Earth does, even though the two are tilted about the same amount, and that actually has to do with the Moon orbiting around Earth. Earth and Mars have a similar spin precession frequency, which matches the orbital oscillation–the ingredients for a spin-orbit resonance.

But Earth has a massive Moon, which pulls on Earth’s spin axis and drives it to precess faster. This slightly faster precession prevents it from experiencing spin orbit resonances. So, the Moon stabilizes Earth’s obliquity, and Earth doesn’t wobble on its axis as much as Mars does.

Exoplanet seasons

Thousands of exoplanets, or planets outside our solar system, have been discovered over the past few decades. My research group wanted to understand how habitable these planets are, and whether these exoplanets also have wild obliquities, or whether they have moons to stabilize them like Earth does.

To investigate this, my group has led the first investigation on the spin-axis variations of exoplanets.

We investigated Kepler-186f, which is the first discovered Earth-sized planet in a habitable zone. The habitable zone is an area around a star where liquid water can exist on the surface of the planet and life may be able to emerge and thrive.

Unlike Earth, Kepler-186f is located far from the other planets in its solar system. As a result, these other planets have only a weak effect on its orbit and movement. So, Kepler-186f generally has a fixed obliquity, similar to Earth. Even without a large moon, it doesn’t have wildly changing or unpredictable seasons like Mars.

Looking forward, more research into exoplanets will help scientists understand what seasons look like throughout the vast diversity of planets in the universe.

Disclaimer: Gongjie Li receives funding from NASA.

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Signs of humanity have traveled through space ever since the very first radio signals left the Earth’s atmosphere. We even made concerted efforts to broadcast evidence of our existence through projects like the historic Voyager spacecraft recordings—but an official intergalactic tourism campaign advertising alien vacations to the “Horse Capital of the Word?” That’s a first.

[ Related: How scientists decide if they’ve actually found signals of alien life ]

The Lexington Convention and Visitors Bureau (VisitLEX) recently turned to University of Kentucky professor and longtime SETI advocate, Robert Lodder, to assemble experts from various disciplines including linguistics, philosophy, and design to attract a unique target audience: (potential) extraterrestrial lifeforms. More specifically, any extraterrestrial life possibly residing within the TRAPPIST-1 system.

Located approximately 40 light-years away in the Leo constellation, TRAPPIST-1 is by far the most studied planetary system outside of our own. There, seven rocky planets orbit a small red dwarf star, three of which reside within its “Goldilocks zone”—the region astrobiologists believe could be conducive to supporting life.

“Many previous transmissions have employed the language of mathematics for communication, and our team did, too,” Lodder tells PopSci. “But we decided that extraterrestrials might be more interested in things unique to Planet Earth than Universal Truths like mathematics, so if we seek to attract visitors, it would be best to send something interesting and uniquely Earth.”

Collaborators ultimately decided on a package including black-and-white photographs of rolling Kentucky bluegrass hills, an audio recording of local blues legend, Tee Dee Young, and an original bitmap illustration—a type of image in which programmers use basic coding to create a grid with shaded blocks that form rudimentary images. Among other subjects, this bitmap art includes renderings of humans, horses, the elements necessary for life (as we know it), alongside the chemical composition maps of ethanol and water, aka alcohol—more specifically to Kentucky, bourbon.

With the message’s contents compiled, Lodder’s team then converted their advertisement into a one-dimensional array of light pulses using a computer-laser interface aimed at TRAPPIST-1. On a clear, dark autumn evening, VisitLEX hosted researchers and local guests at Kentucky Horse Park to fire off their tourism package into space.

While lasers are increasingly replacing radio communications in space due their increased data storage capabilities and lower costs, transmissions must be strong enough to travel millions of miles without degrading. This requires equally strong equipment, such as the Deep Space Optical Communications array aboard NASA’s Psyche spacecraft.

VisitLEX’s laser is far weaker than NASA’s equipment, but Lodder believes that at least some of the transmission’s light photons “will almost certainly” reach TRAPPIST-1. That said, it’s difficult to know if there will be enough photons to fully decode their message.

“The alien receiving technology could be worse than ours, or much better,” says Lodder.

[ Related: JWST just scanned the skies of potentially habitable exoplanet TRAPPIST-1 b ]

Regardless, if ETs ever do make a pitstop in Lexington because of VisitLEX’s interstellar commercial, it likely won’t happen until at least the year 2103—40 light-years for the broadcast to reach TRAPPIST-1, followed by another 40 light-years to travel the approximately 235-million mile trek over to Earth, assuming they’re capable of traveling at the speed of light. It all might sound like a lot both logistically and technologically, but both VisitLEX and Lodder’s team swear it’s worth the planning.

[ Related: To set the record straight: Nothing can break the speed of light ]

If there’s anyone out there listening and able to pick up this kind of admittedly weak signal—and if they have a taste for oak barrel aged bourbon and/or horses—well…

Update 1/12/24 9:00am: PopSci received the following response from Jan McGarry, Next Generation Satellite Laser Ranging Systems Deputy Lead at the NASA Goddard Space Flight Center, and her retired colleague, John Degnan:
“The distance to the nearest star is 2 light years away or many orders of magnitude farther than the edge of our solar system (Pluto). Since the strength of a laser communications link is proportional to 1 divided by the distance squared, it is highly unlikely that a laser system would be able to transfer any meaningful amount of information over that distance let alone one 20 times farther away where the signal would be 400 times smaller.”

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This article was originally featured in The Conversation.

Imagine you’re a farmer searching for eggs in the chicken coop–but instead of a chicken egg, you find an ostrich egg, much larger than anything a chicken could lay.

That’s a little how our team of astronomers felt when we discovered a massive planet, more than 13 times heavier than Earth, around a cool, dim red star, nine times less massive than Earth’s Sun, earlier this year.

The smaller star, called an M star, is not only smaller than the Sun in Earth’s solar system, but it’s 100 times less luminous. Such a star should not have the necessary amount of material in its planet-forming disk to birth such a massive planet.

The Habitable Zone Planet Finder

Over the past decade, our team designed and built a new instrument at Penn State capable of detecting the light from these dim, cool stars at wavelengths beyond the sensitivity of the human eye–in the near-infrared–where such cool stars emit most of their light.

Attached to the 10-meter Hobby-Eberly Telescope in West Texas, our instrument, dubbed the Habitable Zone Planet Finder, can measure the subtle change in a star’s velocity as a planet gravitationally tugs on it. This technique, called the Doppler radial velocity technique, is great for detecting exoplanets.

“Exoplanet” is a combination of the words extrasolar and planet, so the term applies to any planet-sized body in orbit around a star that isn’t Earth’s Sun.

Thirty years ago, Doppler radial velocity observations enabled the discovery of 51 Pegasi b, the first known exoplanet orbiting a Sunlike star. In the ensuing decades, astronomers like us have improved this technique. These increasingly more precise measurements have an important goal: to enable the discovery of rocky planets in habitable zones, the regions around stars where liquid water can be sustained on the planetary surface.

The Doppler technique doesn’t yet have the capabilities to discover habitable zone planets the mass of the Earth around stars the size of the Sun. But the cool and dim M stars show a larger Doppler signature for the same Earth-size planet. The lower mass of the star leads to it getting tugged more by the orbiting planet. And the lower luminosity leads to a closer-in habitable zone and a shorter orbit, which also makes the planet easier to detect.

Planets around these smaller stars were the planets our team designed the Habitable Zone Planet Finder to discover. Our new discovery, published in the journal Science, of a massive planet orbiting closely around the cool dim M star LHS 3154–the ostrich egg in the chicken coop–came as a real surprise.

LHS 315b: The planet that should not exist

Planets form in disks composed of gas and dust. These disks pull together dust grains that grow into pebbles and eventually combine to form a solid planetary core. Once the core is formed, the planet can gravitationally pull in the solid dust, as well as surrounding gas such as hydrogen and helium. But it needs a lot of mass and materials to do this successfully. This way to form planets is called core accretion.

A star as low mass as LHS 3154, nine times less massive than the Sun, should have a correspondingly low-mass planet forming disk.

A typical disk around such a low-mass star should simply not have enough solid materials or mass to be able to make a core heavy enough to create such a planet. From computer simulations our team conducted, we concluded that such a planet needs a disk at least 10 times more massive than typically assumed from direct observations of planet-forming disks.

A different planet formation theory, gravitational instability–where gas and dust in the disk undergo a direct collapse to form a planet – also struggles to explain the formation of such a planet without a very massive disk.

Planets around the most common stars

Cool, dim M stars are the most common stars in our galaxy. In DC comics lore, Superman’s home world, planet Krypton, orbited an M dwarf star.

Astronomers know, from discoveries made with Habitable Zone Planet Finder and other instruments, that giant planets in close-in orbits around the most massive M stars are at least 10 times rarer than those around Sunlike stars. And we know of no such massive planets in close orbits around the least massive M stars–until the discovery of LHS 3154b.

Understanding how planets form around our coolest neighbors will help us understand both how planets form in general and how rocky worlds around the most numerous types of stars form and evolve. This line of research could also help astronomers understand whether M stars are capable of supporting life.

Written by Suvrath Mahadevan, Guðmundur Kári Stefánsson, and Megan Delamer.

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For the first time, astronomers using data from the Keck II telescope have detected the presence of an infrared aurora on the planet Uranus. The discovery could shed light on some of the unknown properties of the magnetic fields of our solar system’s planets. It could also help explain why a planet so far from the sun is hotter than it should be. The findings are described in a study published on October 23 in the journal Nature Astronomy. 

[Related: Uranus got its name from a very serious authority.]

The NIRSPEC instrument (Near InfraRed SPECtrograph) at the Keck Observatory in Hawaii  was used to collect 6 hours of observations of Uranus in 2006. The study’s authors carefully studied 224 images to find signs of a specific particle–ionized triatomic hydrogen or H3+. They found evidence of H3+ in the data after collisions with charged particles. The emission created an infrared auroral glow over Uranus’ northern magnetic pole. The image itself is an artist’s rendition of the infrared aurora, superimposed on a Hubble Space Telescope image of Uranus.

Uranian auroras vs. Earth auroras

Auroras on the planet Uranus are caused when charged particles from the sun interact with the planet’s magnetic field the same way they do on Earth. The particles are funneled along magnetic field lines toward the magnetic poles. When they enter the Uranian atmosphere, the charged particles bump into atmospheric molecules. This causes the molecules to glow. 

The dominant gasses in Uranus’ atmosphere are hydrogen and helium and they are at much lower temperatures than on Earth. The presence of these gasses at these temperatures cause Uranus’ auroras to predominantly glow at ultraviolet and infrared wavelengths. By comparison, auroras on Earth come from oxygen and nitrogen atoms colliding with the charged particles and the colors are mostly blue, green, and red and can generally be seen with the human eye at the right latitudes. 

Uranus and Neptune are unusual planets in our solar system because their magnetic fields are misaligned with the axes in which they spin. Astronomers haven’t found an explanation for this, but clues could lie in Uranus’s aurora. 

Measuring the infrared

In the study, a team of astronomers used the first measurements of the infrared aurora at Uranus since investigations into the planet began in 1992. The ultraviolet aurorae of Uranus was first observed 1986, but the infrared aurora has not been observed until now, according to the team. 

By analyzing specific wavelengths of light emitted from the planet. With this data, they can analyze the light called emission lines from these planets, which is similar to a barcode. In the infrared spectrum, the lines emitted by the H3+ particles will have different levels of brightness depending on how hot or cold the particle is and how dense this layer of the atmosphere is. The lines then act like a thermometer taking the planet’s temperature.

The astronomers found that there were distinct increases in H3+ density in Uranus’s atmosphere with little change in temperature. This is consistent with ionization that is caused by the presence of an infrared aurora. These measurements can help astronomers understand the magnetic fields on the other outer planets in the solar system. They could also scientists identify other planets that are suitable for supporting life.

[Related: Ice giant Uranus shows off its many rings in new JWST image.]

“The temperature of all the gas giant planets, including Uranus, are hundreds of degrees Kelvin/Celsius above what models predict if only warmed by the sun, leaving us with the big question of how these planets are so much hotter than expected? One theory suggests the energetic aurora is the cause of this, which generates and pushes heat from the aurora down towards the magnetic equator,” study co-author and University of Leicester PhD student Emma Thomas said in a statement. 

Clues to life on exoplanets

According to Thomas, most of the exoplanets astronomers have discovered are in the sub-Neptune category, so they are a similar size as Neptune and Uranus. Similar magnetic and atmospheric characteristics could also exist on these exoplanets. Uranus’s aurora directly connects to the planet’s magnetic field and atmosphere, so studying it can help astronomers make predictions about the atmospheres and magnetic fields and their suitability for supporting life.

These results may also provide insight into a rare phenomenon on Earth called geomagnetic reversal. This occurs when the north and south poles switch hemisphere locations. According to NASA, pole reversals are pretty common in Earth’s geologic history and the last one occurred roughly 780,000 years ago. Paleomagnetic records show that over the last 83 million years, Earth’s magnetic poles have reversed 183 times. They’ve also reversed at least several hundred times in the past 160 million years. The time intervals between these reversals have fluctuated, but average about 300,000 years.

“We don’t have many studies on this phenomena and hence do not know what effects this will have on systems that rely on Earth’s magnetic field such as satellites, communications and navigation,” said Thomas. “However, this process occurs every day at Uranus due to the unique misalignment of the rotational and magnetic axes. Continued study of Uranus’s aurora will provide data on what we can expect when Earth exhibits a future pole reversal and what that will mean for its magnetic field.”

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About 40 light years away, a system of seven Earth-sized planets orbit a star that is much cooler and smaller than our sun— the exoplanetary system called TRAPPIST-1. When these exoplanets were discovered in 2016, astronomers speculated that they could one day support humans. Three of those worlds are located in the star’s habitable zone, also called the “Goldilocks zone,” where the conditions for life could be “just right.” Now, astronomers using the James Webb Space Telescope (JWST) have made important progress in understanding the atmosphere of one of its potentially habitable planets.

[Related: JWST’s double take of an Earth-sized exoplanet shows it has no sky.]

JWST observations ruled out the possibilities for a clear, extended atmosphere, failing to detect elements such as hydrogen. The telescope’s new detections also cut through the interference of the star at the center of this system, avoiding what astronomers call stellar contaminations. The findings are detailed in a study published September 22 in The Astrophysical Journal Letters.

The new study specifically sheds light on the nature TRAPPIST-1 b, the exoplanet that is closest to the system’s central star. The team from institutions in the United States and Canada used the JWST’s NIRISS instrument to observe TRAPPIST-1 b during two transits, when the planet passed in front of its star. 

The team used a technique called transmission spectroscopy to look deeper into the distant world. They saw the unique fingerprint left by the molecules and atoms that were found within the exoplanet’s atmosphere. “These are the very first spectroscopic observations of any TRAPPIST-1 planet obtained by the JWST, and we’ve been waiting for them for years,” study co-author and Université de Montréal doctoral student Olivia Lim said in a statement. 

In the past, stars at the center of solar systems may have hampered our understanding of far-off atmospheres. That’s because these suns can create “ghost signals” which fool observers into thinking they are seeing a particular molecule in the exoplanet’s atmosphere. This phenomenon, stellar contamination, is the influence of a star’s own features on the measurements of an exoplanet’s atmosphere.  A sun’s dark spots and bright faculae, or bright spots on its surface, can warp the chemical fingerprints that telescopes detect.

“In addition to the contamination from stellar spots and faculae, we saw a stellar flare, an unpredictable event during which the star looks brighter for several minutes or hours,” said Lim. “This flare affected our measurement of the amount of light blocked by the planet. Such signatures of stellar activity are difficult to model but we need to account for them to ensure that we interpret the data correctly.”

The team also used the observations to explore a range of atmospheric models for TRAPPIST-1 b. They ruled out the existence of cloud-free, hydrogen-rich atmospheres, which means that TRAPPIST-1 b likely does not have a clear and extended atmosphere around it. However, the data could not confidently rule out the possibility of a thinner atmosphere, perhaps made up of pure water, carbon dioxide, or methane. 

[Related: The James Webb Space Telescope just identified its first exoplanet.]

According to the team, this result underscores the importance of taking stellar contamination into account when planning future observations of all exoplanetary systems. This consideration is especially true for systems like TRAPPIST-1, because the system is centered around a red dwarf star which can be particularly active with frequent flare events and dark spots.

More observations will be needed to determine exactly what kind of atmosphere is surrounding this exoplanet and if it could support human life. “This is just a small subset of many more observations of this unique planetary system yet to come and to be analyzed,” study co-author and Université de Montréal astronomer René Doyon said in a statement. “These first observations highlight the power of NIRISS and the JWST in general to probe the thin atmospheres around rocky planets.”

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While it takes the Earth 365 days to revolve around our star (aka the sun), the exoplanet Beta Pictoris b takes 23.6 Earth years to orbit its star. Now, an astrophysicist and exoplanet imager at Northwestern University has used 17 years of footage to create a time-lapse video of this almost complete orbit of the giant planet around its star.

[Related: New image reveals a Jupiter-like world that may share its orbit with a ‘twin’.]

Beta Pictoris b is an enormous planet that has 12 times the mass of the gas giant Jupiter. It’s about 63 lightyears away from the Earth in the constellation Pictor. The whopping planet is about 10 times further away from its star than the Earth is from the sun, and Beta Pictoris b is  about 1.75 times as massive and 8.7 times more luminous than our sun. 

Astrophysicist Jason Wang used real time footage collected between 2003 and 2020 and condense the 17-year-long journey into 10 seconds showing Beta Pictoris b making roughly 75 percent of one full orbit of its star. 

“We need another six years of data before we can see one whole orbit,” Wang said in a statement. “We’re almost there. Patience is key.”

This very young planet is only 20 to 26 million years old and was first imaged in 2003. At the time, its size and brightness made it easier to spot compared to the galaxy’s other exoplanets. 

“It’s extremely bright,” Wang said. “That’s why it’s one of the first exoplanets to ever be discovered and directly imaged. It’s so big that it’s at the boundary of a planet and a brown dwarf, which are more massive than planets.”

Wang first constructed his first time-lapse footage of the Beta Pictoris b with five years of its circuit. He started working with a local high school student named Malachi Noel who used AI-driven image-processing techniques to uniformly analyze archival imaging data from the Gemini Observatory’s Gemini Planet Imager and the European Southern Observatory’s NACO and SPHERE instruments.

“Due to the long time-range, there was a lot of diversity among the datasets, which required frequent adaptations to the image processing,” Noel said in a statement. “I really enjoyed working with the data. While it is too early to know for sure, astrophysics is definitely a career path I am seriously considering.” 

After the data was uniformly processed, Wang used an algorithmic technique called motion interpolation to fill in the gaps to make a continuous video. This kept the image of the exoplanet looking more smooth as it orbits through space. 

“If we just combined the images, the video would look really jittery because we didn’t have continuous viewing of the system every day for 17 years,” Wang said. “The algorithm smooths out that jitter, so we can imagine how the planet would look if we did see it every day.”

Wang used a technology called adaptive optics to assemble the video, which also helped to  correct the image blurring that Earth’s atmosphere causes and suppress the glare of the central star in the system. The star’s glare is still so intense that it outshines Beta Pictoris b when it gets too close. 

[Related: The Milky Way’s shiniest known exoplanet has glittering metallic clouds.]

Wang hopes exoplanet videos give viewers a unique look into planetary motion and demonstrates the inner workings of the universe. 

“A lot of times, in science, we use abstract ideas or mathematical equations,” Wang said. “But something like a movie—that you can see with your own eyes—gives a visceral kind of appreciation for physics that you wouldn’t gain from just looking at plots on a graph.”

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Researchers using Chile’s Atacama Large Millimeter/submillimeter Array of telescopes (ALMA) may have found a rare “sibling” sharing the same orbit of a Jupiter-like planet about 370 light-years away from Earth in the Centaurus constellation. The newly discovered twin shares the same orbit as PDS 70b around a young star in the  PDS 70 system. 

[Related: How engineers saved NASA’s new asteroid probe when it malfunctioned in space.]

While two Jupiter-like planets, PDS 70b and PDS 70c, are already known to orbit this star, the team detected a cloud of debris within PDS 70b’s orbital path following this planet’s orbit. The debris could be the beginnings of a new planet, or even the remnants of one that is already formed. The findings were published on July 19 in the journal Astronomy and Astrophysics. If confirmed, this discovery would present the strongest known evidence that two exoplanets can share one orbit. 

“Two decades ago it was predicted in theory that pairs of planets of similar mass may share the same orbit around their star, the so-called Trojan or co-orbital planets. For the first time, we have found evidence in favor of that idea,” Olga Balsalobre-Ruza study co-author and a student at Centre for Astrobiology in Madrid, Spain said in a statement.

Rocky bodies that are in the same orbit as a planet called Trojans are common throughout our solar system. Jupiter’s more than 12,000 known Trojan asteroids that are in the same orbit as our sun are the most common example. The asteroids in Jupiter’s orbit were named after heroes of the Trojan War when they were first discovered, which is why the catch-all name Trojans is used to describe these celestial objects. 

Astronomers have speculated that systems like this could exist around a star other than our sun—appropriately called exotrojans.

“Exotrojans have so far been like unicorns: they are allowed to exist by theory but no one has ever detected them,” study co-author and researcher at the Centre for Astrobiology Jorge Lillo-Box said in a statement.

In this new study, an international team of scientists analyzed archival ALMA observations of the PDS 70 system system, and spotted the cloud of debris at the location in PDS 70b’s orbit where Trojans are expected to exist. Trojans typically occupy two extended regions in a planet’s orbit where the combined gravitational pull of the star and the planet can trap material called Lagrangian zones/points. By studying these two regions of PDS 70b’s orbit, the team noticed a faint signal coming from one of them, indicating that a cloud of debris that has a mass roughly two times that of our moon might be present. 

[Related: The James Webb Space Telescope just identified its first exoplanet.]

This cloud of debris could point to an existing Trojan world in this system, or a planet in the process of forming, according to the team.

 “Who could imagine two worlds that share the duration of the year and the habitability conditions? Our work is the first evidence that this kind of world could exist,” said  Balsalobre-Ruza. “We can imagine that a planet can share its orbit with thousands of asteroids as in the case of Jupiter, but it is mind blowing to me that planets could share the same orbit.”

Patience will be key to fully confirm this detection. The team will have to wait until after 2026, when they plan to use ALMA to see if both PDS 70b and its sibling debris cloud move significantly along their orbit together around the star. 

“The future of this topic is very exciting and we look forward to the extended ALMA capabilities, planned for 2030, which will dramatically improve the array’s ability to characterize Trojans in many other stars,” study co-author and European Southern Observatory Head of the Office for Science Itziar De Gregorio-Monsalvo concluded in a statement.

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Few scientific tools get introduced in a press conference by the commander-in-chief. But NASA’s James Webb Space Telescope is no ordinary instrument. President Biden unveiled the first image from JWST in July 2022, revealing the sharpest, deepest infrared view of the universe ever taken. And that was only the beginning. 

The solar-powered device, which drifts at a stable point 930,000 miles away from Earth, has since captured giant galaxies from the cosmic dawn; helped researchers discover the most distant and active supermassive black hole; snapped glowing views of Saturn and Jupiter; and found a new world beyond our solar system. It has teased out the details of the atmospheres above exoplanets and made the first-ever in-space detection of a molecule called methyl cation, a building block for the more complex carbon compounds found on Earth. 

The telescope was built on several aerospace innovations. Its mirrors are plated in a microscopic film of gold, optimized to reflect light. Its imagers, which include the Near-Infrared Camera and Mid-Infrared Instrument, allow JWST to look beyond cosmic dust and sense weak and ancient light from up to 13 billion years ago, just 800,000 years after the universe was born. And thanks to far more recent technology, it’s also incredibly easy to set up alerts for when the JWST has captured a new image, so you never miss out.

These remarkable James Webb Space Telescope images show stars, galaxies, and space in all their sparkling glory. What are your favorites?

[Related: The best telescopes for kids]

This post has been updated. It was originally published in July 2023.

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Astronomers from the European Space Agency (ESA) have discovered the shiniest known exoplanet in our universe to date. Named LTT9779 b, this ultra hot exoplanet revolves around its host star every 19 hours and is 262 light-years away from Earth.

[Related: Gritty, swirling clouds of silica surround exoplanet VHS 1256 b.]

In our night sky, the moon and Venus are the brightest objects. Venus’ thick cloud layers reflect 75 percent of the sun’s incoming light, compared to Earth’s cloud layers that just reflect about 30 percent. LTT9779 b and it’s reflective metallic clouds can match Venus’ shininess. Detailed measurements taken by ESA’s Cheops (CHaracterising ExOPlanet Satellite) mission shows that the glittering globe reflects 80 percent of the light that is shone on it by its host star. 

LTT9779 b was first spotted in 2020 by NASA’s Transiting Exoplanet Survey Satellite (TESS) mission and ground-based observations conducted at the European Southern Observatory in Chile. ESA then selected this planet for additional observations as part of the Cheops mission.

At around the same size as the planet Neptune, LTT9779 b is the largest known “mirror” in the universe. According to ESA, it is so reflective due to its metallic clouds that are mostly made of silicate mixed in with metals like titanium. Sand and glass that are used to make mirrors are also primarily made up of silicate. The findings are detailed in a study published July 10 in the journal Astronomy & Astrophysics.

“Imagine a burning world, close to its star, with heavy clouds of metals floating aloft, raining down titanium droplets,” study co-author and Diego Portales University in Chile astronomer James Jenkins, said in a statement. 

The amount of light that an object reflects is called its albedo. Most planets have a low albedo, primarily because they either have an atmosphere that absorbs a lot of light or their surface is rough or dark. Frozen ice-worlds or planets like Venus that boast a reflective cloud layer tend to be the exceptions. 

For the team on this study, LTT9779 b’s high albedo came as a surprise, since the side of the planet that faces its host star is estimated to be around 3,632 degrees Fahrenheit. Any temperature above 212 degrees is too hot for clouds of water to form. On paper, the temperature of LTT9779 b’s atmosphere should even be too hot for clouds that are made of glass or metal.

“It was really a puzzle, until we realized we should think about this cloud formation in the same way as condensation forming in a bathroom after a hot shower,” said co-author and Observatory of Côte d’Azur researcher Vivien Parmentier in a statement. “To steam up a bathroom you can either cool the air until water vapor condenses, or you can keep the hot water running until clouds form because the air is so saturated with vapor that it simply can’t hold any more. Similarly, LTT9779 b can form metallic clouds despite being so hot because the atmosphere is oversaturated with silicate and metal vapors.”

[Related: JWST’s double take of an Earth-sized exoplanet shows it has no sky.]

In addition to being a shiny happy exoplanet, LTT9779 b also is remarkable because it is a planet that shouldn’t really exist. Its size and temperature make it an “ultra-hot Neptune,” but there are no known planets of its size in mass that have been found orbiting this close to their host star. This means that LTT9779 b lives in the “hot Neptune desert,” a planet whose atmosphere is heated to more than 1,700 degrees.

“’We believe these metal clouds help the planet to survive in the hot Neptune desert,” co-author and astronomer at Marseille Astrophysics Laboratory Sergio Hoyer said in a statement. “The clouds reflect light and stop the planet from getting too hot and evaporating. Meanwhile, being highly metallic makes the planet and its atmosphere heavy and harder to blow away.”

While its radius is about 4.7 times as big as Earth’s, one year on LTT9779 b takes only 19 hours. All of the previously discovered planets that orbit their star in less than one day are either  gas giants with a radius that is at least 10 times earth (called hot Jupiters) or rocky planets that are smaller than two Earth radii.

“It’s a planet that shouldn’t exist,” said Vivien. “We expect planets like this to have their atmosphere blown away by their star, leaving behind bare rock.”

Cheops is the first of three ESA missions dedicated to studying the exciting world of exoplanets. In 2026, it will be joined by the Plato mission which will focus on Earth-like planets that could be orbiting at a distance from their star that supports life. Ariel is scheduled to join in 2029, specializing in studying the atmospheres of exoplanets. 

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Earth’s atmosphere is absolutely crucial for life on our blue marble, so it’s no wonder astronomers are eager to peer into the clouds of exoplanets around other stars. One popular far-flung world—TRAPPIST-1c—was so appealing to researchers because it was previously thought to be shrouded in a thick layer of carbon dioxide. But new observations from the James Webb Space Telescope (JWST), however, have revealed that it is more likely to be a barren rock, with no atmosphere in sight. 

When astronomers try to get a handle on how many planets out in space could support life, the first place to look is a rocky world like Earth, where the planet has a sturdy surface for biology to take root. “Small planets are abundant in the galaxy,” says Sebastian Zieba, exoplanet researcher at the Max Planck Institute for Astronomy and Leiden Observatory and the lead author of a study published in Nature on the new TRAPPIST-1c observations. “At least 20 to 50 percent of stars host a planet similar in size to the Earth.” Astronomers still don’t know much about these rocky planets’ atmospheres, or whether they have one at all. It’s also an open question whether M dwarf stars, the abundant kind of star TRAPPIST-1c orbits, might destroy those planets’ atmospheres, rendering them uninhabitable. 

JWST is quickly changing that reality. “There is no other observatory right now which can give us precise measurements like these,” Zieba adds—studying infrared light is where the telescope excels. The fingerprints of many molecules important for life show up in those infrared wavelengths, but these are challenging to detect. To make these measurements, JWST has to be far beyond freezing, a meager 7 kelvin (equivalent to -500°F).

“For many years, scientists have been modeling the atmospheres of these worlds,” says Daria Pidhorodetska, an astronomer at the University of California, Riverside not involved in the new research. “To finally get to see the real data come from JWST feels like a dream come true.”

[Related: A whopping seven Earth-size planets were just found orbiting a nearby star]

Observers have focused so much attention on TRAPPIST-1c for a good reason: it’s by far the best target to study rocky, Earth-sized planets in detail, since it’s nearby (about 40 light years away) and easy to see with current tech. “You would obviously start with the lowest-hanging fruit,” says Zieba. TRAPPIST-1c orbits the star TRAPPIST-1, which hosts a family of seven Earth-sized planets. Three of them might be in the star’s habitable zone. 

That solar system offers a unique chance for astronomers to look at Earth-like planets at different temperatures, getting a glimpse at a spectrum of possibilities for rocky worlds. By determining what molecules surround these worlds, “we may be able to infer whether they could indeed support life,” says University of California, Los Angeles astronomer Judah Van Zandt, who was not involved in the paper. 

[Related: What Earth looks like to far-out celestial bodies]

TRAPPIST-1 isn’t like our sun, though. It’s a small red star called an M dwarf, which happens to be the most common star type in the galaxy. One of the big questions in astronomy right now is: Can planets around M dwarfs keep their atmospheres, or do the brutal flares of these powerful little stars burn the skies away? If astronomers find that most planets around M dwarfs are bare rocks, maybe sun-like stars are necessary for life after all. So far, there are two strikes against M dwarfs—not only does TRAPPIST-1c lack an atmosphere, but a publication from earlier this year showed that TRAPPIST-1b is also barren. 

We will soon find out whether TRAPPIST-1c’s neighbors follow this pattern—or upend it. All seven TRAPPIST-1 planets will be observed with JWST within the year, and it’s yet to be seen if others may have kept their clouds. And even if they don’t, as Zieba says, “this is obviously just one M-type star.” Astronomers will have to observe many more planets to truly judge whether M dwarfs are fit to support life.

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Our solar system has a suite of eight planets—rocky Mars and Earth, the ice giants, and massive gas planets—but other stars often have a much smaller group. Some suns have just one exoplanet orbiting around them. These loner worlds are often one specific type: A huge gas giant that orbits very close to its star, known as a hot Jupiter.

A newly discovered exoplanet, however, has challenged this view, showing that maybe not all hot Jupiters go solo. Last week, astronomers announced that a hot Jupiter orbiting a star 400 light years away has a pal: It shares its solar system with WASP-84c, a rocky planet so large it’s known as a super-Earth. This discovery was made public as a preprint, a research paper that has yet to undergo peer review, and submitted to the journal Monthly Notices of the Royal Astronomical Society for official publication.

Hot Jupiters are a weird kind of planet. We don’t have any in our own solar system. Until the first was spotted, astronomers never expected them to exist. Gas giants like Jupiter usually only form far away from their stars, where things are cool enough for gas to stay safe from blazing solar heat. If a Jupiter-like planet has to be born at a distance, then, how can it get so close to its star? 

Astronomers have three main theories for how this happens. Two are gentle, and one is catastrophic. First, a hot Jupiter could move inward from its birthplace due to little gravitational nudges from the protoplanetary disk, a collection of dust and gas used to form planets in a star’s youth. Second, maybe we’re wrong about the theory that Jupiter-like planets must form far from stars. Instead, these planets are simply born where we see them. Both of these scenarios would allow hot Jupiters to have smaller friend planets hanging out nearby.

[Related: Ridiculously hot gas giant exoplanet is about to be swallowed by its dying sun]

But the third option is the most dynamic. Jupiters could form far out, but then encounter other planets that change the gas giants’ orbits. The gravity of the other planets would force a hot Jupiter into a stretched out, elliptical path, and then the gravity of the star would pull the gas giant in close, resulting in a circular, super-short orbit. In this violent dance, any low mass planets would be destroyed—creating the lonely hot Jupiter.

The best theory for the origin of this particular hot Jupiter, named WASP-84b, is the first—that a disk helped shepherd the planet through the solar system. Previous observations showed that the gas giant’s spin is aligned with the star’s, a sign that the large planet migrated within the protoplanetary disk instead of pinballing around with other planets. The discovery of super-Earth WASP-84c now adds more evidence to the case that this hot Jupiter formed with a nudge, not a planet-destroying bang—and that scenario may be more common than previously thought.

WASP-84c joins a growing list of smaller planetary buddies to hot Jupiters: WASP-47 b, Kepler 730 b, and WASP-132 b, to name a few. “The discovery of low-mass planetary companions like WASP-84c suggests that not all hot Jupiter systems formed under violent scenarios, as previously thought,” says lead author Gracjan Maciejewski from the Institute of Astronomy of the Nicolaus Copernicus University in Torun, Poland.

Maciejewski and his colleagues used NASA’s Transiting Exoplanet Survey Satellite (TESS) to spot WASP-84c. TESS hunts for exoplanets using the transit method, where a telescope watches a star for teensy dips in its brightness, caused by a dark planet passing in front. 

[Related: A deep-space telescope spied an exoplanet so hot it can vaporize iron]

WASP-84c “was too small in radius to have been discovered by the original WASP survey, who discovered the hot Jupiter,” according to Caltech astronomer Juliette Becker, who is not affiliated with the new discovery. “It’s a great example of what TESS can do,” she adds.

With the transit method, astronomers can figure out a planet’s dimensions. However, to find out how much it weighs, they need different data, from another exoplanet-detecting technique known as the radial velocity method. When WASP-84c’s discoverers gathered this extra data, they determined that the planet has about 15 times the mass of Earth. Like our Blue Marble, it’s probably made of iron and rocks, too.

Jonathan Brande, a University of Kansas astronomer not involved in the discovery, thinks such discoveries will become even more common as the James Webb Space Telescope brings in new exoplanet data, deepening our understanding of how these planet pairs came to be. “I would not be surprised if we see further results on this system in the near future,” he says.

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Our asteroid belt is home to more than a million space rocks, varying in size from a dwarf planet to dust particles, which float between Jupiter and Mars. Astronomers have just discovered another such belt—but this one circles a different star, not our sun.

NASA’s James Webb Space Telescope (JWST) detected this asteroid belt around the star Fomalhaut, only 25 light-years away. For years, scientists have studied Fomalhaut’s debris disk, a collection of rocky, icy, dusty bits from all the collisions that happen while planets are being created. This new data, published today in Nature Astronomy, shows the system in unprecedented detail, uncovering fingerprints of hidden worlds and evidence for planets smashing together.

Many telescopes have pointed to Fomalhaut over the years: the Spitzer Space Telescope, the Atacama Large Millimeter Array (ALMA) in the high desert of Chile, and even the Hubble Space Telescope. Fomalhaut, which is much younger than our sun, may be a good likeness of our solar system near birth; since astronomers can’t time travel back to our sun’s formation, they instead observe other young stars, using these still-forming planetary systems as examples of what the process of making planets can look like.

Fomalhaut is an appealing choice to astronomers because it’s nearby, meaning it’s easier for astronomers to notice fine details. “This system was definitely one of the first we wanted to observe with JWST,” says co-author Marie Ygouf, research scientist at NASA’s Jet Propulsion Lab.

Before JWST, other observations revealed that Fomalhaut is surrounded by a ring of dust analogous to our own solar system’s Kuiper Belt, which contains all the little bits of ice and rock beyond Neptune. The new data from NASA’s superlative space telescope spot not only this outer ring, but also an inner ring more analogous to the asteroid belt. There’s a third feature, too—a giant clump of dust, lovingly referred to as the Great Dust Cloud. 

[Related: These 6 galaxies are so huge, they’ve been nicknamed ‘universe breakers’]

Between Fomalhaut’s outer Kuiper-Belt-like ring and its inner asteroid-belt-like ring is a gap. “The new gap that we see hints at the presence of an ice-giant mass planet, which would be an analog of what we see in the solar system,” like Neptune or Uranus, says lead author András Gáspár, astronomer at the University of Arizona. This unseen planet could be “carving out the gaps” via gravity, explains fellow Arizona astronomer and co-author Schuyler Wolff.

Fomalhaut’s asteroid belt has a curious tilt, appearing at a different angle from the outer ring, as though something knocked it off kilter. A knock, in fact, might explain the misalignment, the researchers say—a major collision could have tilted the asteroid belt, creating the massive dust cloud, too. 

All signs in Fomalhaut “point to a solar system that is alive and active, full of rocky bodies smashing into each other,” says co-author Jonathan Aguilar, staff scientist at Space Telescope Science Institute, home of JWST’s mission control.

JWST was uniquely suited to take these photos of Fomalhaut’s dust. The dust glows brightest in the mid-infrared, at long wavelengths unreachable by most other observatories. A particularly powerful telescope is necessary, too, to resolve enough details—and JWST is the only scope with both these features. The space telescope’s Mid-Infrared Instrument (MIRI) also has a coronagraph, a small dot to block out a bright star and reveal the surrounding dust.

“Mid-infrared wavelengths are so important for debris disk observations because that’s where you observe dust emission, and the distribution of dust tells you a lot about what’s going on,” says Aguilar. The new view of Fomalhaut “showcases the scientific power of JWST and MIRI even just a year into operations,” he adds.

[Related: NASA sampled a ‘fluffy’ asteroid that could hold clues to our existence]

It’s certainly interesting to see what our solar system may have looked like in its infancy—but Fomalhaut isn’t an exact clone. Fomalhaut’s Kuiper Belt and asteroid belt doppelgangers are more spread out and contain more material than those features in our solar system. Although Fomalhaut has more movement and smashing than our solar system does now, our planets had a similar phase in the distant past, known as the Late Heavy Bombardment. Astronomers hope debris disks seen by JWST will help them figure out the details of how solar systems are born, and how they grow up to look like our own set of planets.

“We are at this frontier of unexplored territory, and I’m especially excited to see what JWST finds towards planet-forming disks,” says University of Michigan astronomer Jenny Calahan, who was not involved in the new findings. “Looking at these JWST images I was reminded of the moment that I got glasses for the first time,” adds Calahan. “It just changes your whole perspective when the world (or a debris disk) comes into focus at a level that you aren’t used to.”

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If you’ve ever been to the beach on a windy day, you’ve likely been treated to the not so fun feeling grains of sand hitting your face. That unpleasant experience would a walk in the park compared to what scientists have now discovered is happening in the atmosphere of the exoplanet VHS 1256 b.

A team of researchers using the James Webb Space Telescope (JWST) found that the planet’s clouds are made up of silicate particles that range in size from tiny specks to small grains.  The silicates in the clouds are swirling in nearly constant cloud cover. Silicates are common in our solar system and make up about 95 percent of Earth’s crust and upper mantle.

[Related: These 6 galaxies are so huge, they’ve been nicknamed ‘universe breakers.’]

During VHS 1256 b’s 22-hour day, the atmosphere is continuously rising, mixing, and moving. This motion brings hotter material up and pushes colder material down, the way hot air rises  and cool air sinks on Earth. The brightness that results from this air shifting is so dramatic that the team on the study say it is the most variable planetary-mass object known to date. 

The findings were published March 22 in the The Astrophysical Journal Letters. The team also found very clear detections of carbon monoxide, methane, and water using JWST’s data and even evidence of carbon dioxide. According to NASA, it is the largest number of molecules ever identified all at once on a planet outside our solar system.

VHS 1256 b is about 40 light-years away from Earth and orbits two stars over a 10,000-year period. “VHS 1256 b is about four times farther from its stars than Pluto is from our Sun, which makes it a great target for Webb,” said study co-author and University of Arizona astronomer Brittany Miles, in a statement. “That means the planet’s light is not mixed with light from its stars.” 

The temperature in the higher parts of its atmosphere where the silicate clouds churn daily reach about 1,500 degrees Fahrenheit. JWST detected both larger and smaller silicate dust grains within these clouds that are shown on a spectrum. 

“The finer silicate grains in its atmosphere may be more like tiny particles in smoke,” said astronomer and co-author Beth Biller of the University of Edinburgh in Scotland, in a statement. “The larger grains might be more like very hot, very small sand particles.”

[Related: JWST has changed the speed of discovery, for better or for worse.]

Compared to more massive brown dwarfs, VHS 1256 b has low gravity, so its silicate clouds can appear and remain higher up in its atmosphere where JWST can detect them. It is also quite young as far as planets are concerned, at only 150 million years old. As with most young humans, it’s going through some turbulent times as it ages. 

The team says that these findings are similar to the first “coins” pulled out of a treasure chest of data that they are only beginning to rummage through. “We’ve identified silicates, but better understanding which grain sizes and shapes match specific types of clouds is going to take a lot of additional work,” said Miles. “This is not the final word on this planet – it is the beginning of a large-scale modeling effort to fit Webb’s complex data.”

While these features have been spotted on other planets in the Milky Way by other telescopes, only one at a time was typically identified, according to the team. They used JWST’s Near-Infrared Spectrograph (NIRSpec) and the Mid-Infrared Instrument (MIRI) to collect the data and says that there will be much more to learn about VHS 1256 b as scientists sift through the data.

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Star Trek fans knew they would lose the planet Vulcan someday in a fiery implosion at the hands of the Romulans—but they probably didn’t expect it to lose the planet in real life, too. Now reality is once again following fiction: The exoplanet once considered to be the real Vulcan has been erased, based on a new analysis of old data.

The 2018 discovery of the exoplanet known as 40 Eri b, which is located around the real-life star canonically orbited by Spock’s fictional homeworld, has turned out to be a false alarm. In a new research paper accepted for publication in the Astronomical Journal, astronomers used years of observations to re-analyze many previous exoplanet detections, including that of 40 Eri b. Unfortunately, astronomers hadn’t actually found Vulcan after all.

“As we continue to study objects with better and more precise instruments, reevaluating things we thought we already knew can lead to new conclusions about what’s really going on,” says Ohio State University astronomer Katherine Laliotis, lead author on the new work. In the case of 40 Eri b, the signal previously thought to be a planet turned out to be activity on the star’s surface. This work, she adds, is “a reminder that re-studying and reproducing already published results is a very valuable use of time.”

40 Eri b was originally detected using the radial velocity method, in which astronomers analyze the different wavelengths of light coming from a star. As a planet orbits a star, it’ll tug on its sun ever so slightly. When this tug pushes the star away from Earth, the star appears redder—thanks to the Doppler effect—and if it moves toward us, it appears bluer. With this method, astronomers believed they found 40 Eri b: A Neptune-sized planet 16 light-years away, so close to its star that a year would last only 42 days. This wouldn’t have been a particularly pleasant or habitable planet, but it made waves thanks to its sci-fi ties.

[Related: Newly discovered exoplanet may be a ‘Super Earth’ covered in water]

Some astronomers, such as NASA astronomer Eric Mamajek, immediately expressed doubts about the supposed detection. That’s because the time it took for this planet to complete one orbit was suspiciously close to the time the star takes to rotate. His suspicions were right. By tracing a feature of the light spectrum known to be part of the star, Laliotis and collaborators confirmed the star’s rotation rate, marking the end of the possible planet 40 Eri b. 

They didn’t specifically set out on a mission to kill Vulcan, though. This work was part of a bigger analysis, looking into all of NASA’s top picks for future exoplanet exploration—and 40 Eridani just happened to be on the list. Astronomers are always collecting new data, observing different stars, but “​​many planetary systems haven’t been officially updated since they were published in the early 2000s,” according to Laliotis.

Astronomers are already starting preparation for the next big space telescope, known as the Habitable Worlds Observatory. This future NASA mission aims to take photos of Earth-like planets around sun-like stars, allowing scientists to directly look into these exoplanets’ atmospheres for oxygen and other signs of life. Laliotis’s work fits right into this plan—she says this study aimed to figure out “what [planetary] systems we already understand well, what systems we have a misunderstanding of, and what systems need to be observed a lot more in the coming years.” This review will help make sure the future telescope’s precious observing time is used wisely.

“NASA is planning to spend billions of dollars on future missions to fly telescopes to study planets,” says Jessie Christiansen, project scientist at NASA’s Exoplanet Archive. “Imagine if this had been one of the targets! It’s not real!”

Although astronomers are, of course, glad to see rigorous scientific work being done, they’ll also admit that they are a bit sad about losing an exoplanet with such a cool sci-fi crossover. “I’m sad whenever any planet gets disproven, but this one hit especially hard because I’ve been using it for a few years now as a provocative, intriguing tie between the real worlds we’re discovering and the fictional worlds we know and love,” says Christiansen, who also started a lively Twitter conversation on the topic.

[Related: In a first, James Webb Space Telescope reveals distant gassy atmosphere is filled with carbon dioxide]

This doesn’t completely rule out a real-world equivalent of Vulcan, though. The Neptune-sized planet discovered in 2018 isn’t there, but it’s possible a smaller planet—one we haven’t seen yet—still exists around the star 40 Eridani. With current technology and observations, astronomers simply can’t detect any planet smaller than 12 times Earth’s mass on an orbit similar to Earth’s. “This means there’s still a chance that Vulcan exists. In fact, there’s even a chance that Vulcan could be in the habitable zone for the star,” says Laliotis.

Even if Vulcan is gone for now, Trekkie astronomers will still find ways to have fun with sci-fi and outer space. “There are still many other planets in the Star Trek universe that haven’t been disproven,” adds Louisiana State University astronomer Alison Crisp. One potential planet orbiting Wolf 359, for example, could still exist—the site of a major Star Trek battle. 

UCLA astronomer Isabella Trierweiler actually sees a way this saga fits into Star Trek canon. “Until 2063, Vulcans are just observing Earth and waiting for us to develop warp capabilities,” Trierweiler says. “Maybe they were able to adjust our observations to hide the planet, maybe they found super strong cloaking devices, or maybe Vulcan was briefly one of those planets that phases in and out of dimensions!” Whatever Vulcan’s fate, humanity has a few more years of technological development ahead of us until we reach these sci-fi dreams. And perhaps those lofty goals will help us find a real planet around 40 Eridani.

The post Sorry, Star Trek fans, the real planet Vulcan doesn’t exist appeared first on Popular Science.

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After launching on Christmas Day 2021, the James Webb Space Telescope (JWST) has continued to dazzle us with its data and discoveries. Now, the multi-mirrored space observatory has identified its first new exoplanet named LHS 475 b. At only 41 light years away from Earth in the constellation Octans, the exoplanet is about 99 percent of our world’s diameter.

After reviewing the targets of interest from NASA’s Transiting Exoplanet Survey Satellite, the team from Johns Hopkins University Applied Physics Laboratory (APL) in Maryland honed in on hints of the exoplanet’s existence with JWST. With only two transit observations (when an exoplanet passes in front of its star), JWST’s Near-Infrared Spectrograph (NIRSpec) captured the distant celestial body clearly. “There is no question that it’s there. Webb’s pristine data validate it,” said Jacob Lustig-Yaeger, an astronomer and astrobiologist at APL, in a statement.

[Related: James Webb Space Telescope reconstructed a ‘star party,’ and you’re invited.]

“The fact that it is also a small, rocky planet is impressive for the observatory,” Kevin Stevenson, an astronomer also from APL, added in the statement,

JWST can characterize the atmosphere of exoplanets that are close to Earth’s size. The team tried to assess LHS 475 b’s atmosphere by analyzing its transmission spectrum. According to NASA, “When starlight passes through the atmosphere of a planet some of the light is absorbed by the atmosphere and some is transmitted through it. The dark lines and dim bands of light in a transmission spectrum correspond to atoms and molecules in the planet’s atmosphere. The amount of light that is transmitted also depends on how dense the atmosphere is and how warm it is.”

The data shows that the exoplanet is an Earth-sized terrestrial (not water covered) world, but it is not known if it has an atmosphere.

“The observatory’s data are beautiful,” noted Erin May, an astrophysicist at APL, in a statement. “The telescope is so sensitive that it can easily detect a range of molecules, but we can’t yet make any definitive conclusions about LHS 475 b’s atmosphere.”

That said, the team can definitely say what is not present. “There are some terrestrial-type atmospheres that we can rule out,” explained Lustig-Yaeger. “It can’t have a thick methane-dominated atmosphere, similar to that of Saturn’s moon Titan.”

While it is possible that the exoplanet doesn’t have an atmosphere, some environmental conditions haven’t been ruled out. One of those conditions is a pure carbon dioxide atmosphere. “Counterintuitively, a 100-percent carbon dioxide atmosphere is so much more compact that it becomes very challenging to detect,” said Lustig-Yaeger. To distinguish a pure carbon dioxide atmosphere from no atmosphere at all will take even more precise measurements that the team is scheduled to receive this summer.

[Related on PopSci+: There is no Planet B.]

JWST also revealed that LHS 475 b is much warmer than Earth. If clouds are detected, it could be more like Venus, which does have a carbon dioxide atmosphere. It also completes an orbit in just two days, which the JWST’s precise light curve from the telescope’s NIRSpec was able to reveal.

Findings like JWST’s also open up possibilities of pinpointing Earth-sized exoplanets orbiting smaller red dwarf stars. “This confirmation highlights the precision of the mission’s instruments,” said Stevenson.

In addition to LHS 475 b, NASA has confirmed 5,000-plus exoplanets with its many deep-space searching tools. The roster is incredibly diverse, with some looking like Mars’s pebbly terrain and others like Jupiter-esque gas giants. Some of them orbit two stars at once, while others orbit long-dead stars. It is very likely that there are hundreds of billions of exoplanets in the Milky Way galaxy alone. JWST will be able to tell scientists even more about these other worlds.

“We have barely begun scratching the surface of what their atmospheres might be like. And it is only the first of many discoveries that it will make,” stated Lustig-Yaeger. “With this telescope, rocky exoplanets are the new frontier.”

Correction (January 19, 2023): The story initially said that when an exoplanet “transits,” it passes in front of its moon, which was incorrect. It passes in front of its star.

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In the past few decades, astronomers have discovered thousands of exoplanets around other stars. Many of those worlds look nothing like the planets in our own solar system. One curious type of exoplanet is the Hot Jupiter, a planet similar in size to our own Jupiter–but, unlike our neighborhood gas giant, these are extremely close to their home stars.

A team of Japanese astronomers recently discovered one of the hottest Jupiters to date, around a star known as HD 167768, as part of their long-running Okayama Planet Search Program that began in 2001. To make the situation even weirder, this planet is around an old, dying star—a place no one would have expected a planet to survive. 

Huanyu Teng, astronomer at the Tokyo Institute of Technology and lead author of this discovery, considers this planet “a relatively lucky find” and “a rare case.”

This new planet, named HD 167768 b, is so close to its parent star that one year there is only 20 Earth days long. This planet is technically considered a warm Jupiter, since Hot Jupiters are defined as having a year shorter than 10 Earth days. But HD 167768 b is a whopping 3,000°F, about the temperature of a jet engine, which is hotter than nearly all other known Hot Jupiters, the study authors say. 

Although it takes a little longer than typical for this Hot Jupiter to complete a circle around its sun, this star has inflated, shortening the distance from its blazing surface to the planet. If most Hot Jupiters orbited stars the size of M&Ms, HD 167768 b’s star is something like a golf ball. The distance between the gas planet and its sun is one-and-a-half times the star’s diameter—for context, you could fit almost 108 of our sun’s lengths within Earth’s orbit. 

[Related: A deep-space telescope spied an exoplanet so hot it can vaporize iron]

Teng and co-authors published the discovery in November 2022 as what’s called a preprint paper, a way for scientists to share work before the expert review required for publication in a journal. In this case, the Hot Jupiter study has been accepted in the Publications of the Astronomical Society of Japan.

Astronomers previously thought the aging process of a star would be “fatal to close-orbiting exoplanets” like HD 167768 b, says University of Kansas astronomer Jonathan Brande, who wasn’t involved in the new report. As stars run out of the fuel that sustains their nuclear fusion, they puff up, expanding their outer layers and often engulfing the closest planets—or so astronomers think. There are still many outstanding questions about what happens at the end of a solar system’s life, including whether planets survive or change as their stars die.

“There have been tens of planets discovered around evolved giant stars, but almost all of these planets are at large distances from their host stars,” says Aurora Kesseli, research scientist at the NASA Exoplanet Science Institute. HD 167768 b “helps to answer some of these questions about what happens to planets when their host stars become giants.”

[Related: Newly discovered exoplanet may be a ‘Super Earth’ covered in water]

There are other curiosities about HD 167768 b, too—it’s in a strange part of the galaxy for a planet to exist. Our Milky Way is shaped like a crepe stuffed within a fluffy pancake, where the crepe is known as the thin disk and the pancake is the thick disk. The stars in the thick disk tend to be much older, and are thought to be less favorable environments for planets to grow up around. We’re in the thin disk–but HD 167768 b was found in the thicker one.

This curious world also shows signs that it’s not alone. HD 167768 b was discovered via the tried-and-true radial velocity method, where astronomers measure the movement of a star to infer hidden planets. The team noticed two more possible planet signals in the data, hinting at neighboring planets orbiting a bit further away from the star—they would have years 41 and 95 Earth-days long. To find out if these neighbors are real, astronomers will need to take a closer look at this system, such as with the Transiting Exoplanet Survey Satellite (TESS). Further observations of the new planet will allow astronomers to dig deeper into questions about old planets, now that they have this excellent specimen to analyze.

We don’t have forever to watch HD 167768 b, though. Teng and collaborators calculate that this planet will only exist for 150 million more years—an absolute blink of the eye for the timescales of the universe. (Earth, meanwhile, should stick around for at least another 5 billion years.) This is an exciting opportunity to see a planet so close to the end of its existence.

“Cosmically, this is just about the last possible time we’ll be able to study the planet,” says Brande. “As the host star is continuing to expand, eventually it will totally eat this planet for dinner.”

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The Kuiper Belt, the donut-shaped ring of icy bodies that stretches far beyond Neptune’s orbit, is home to some of the strangest objects in our solar system. Inside this icy region, there are trillions of comets, asteroids, and heavenly remnants leftover from the earliest days of our solar system, some of which many humans may already be familiar with, like Pluto, Eris, and Makemake. 

Yet one of its most interesting oddities is the dwarf planet, Haumea.

Though it was discovered less than two decades ago, information about the dwarf planet is sparse as Earth-based telescopes have a hard time making precise measurements because of how distant it is. But the little we do know about Haumea suggests that it is an extremely strange and important entity. Shaped almost like a deflated football, the planet spins faster than anything else of its size, whirling on its axis in only four hours. Besides having two moons, Haumea also has a very faint ring system and is covered almost exclusively in crystalline water ice, making it an excellent candidate to investigate whether it might have once hosted life. 

“From an astrobiological perspective, there are a lot of things we don’t yet know about how life got started, even on Earth, and we live here,” says Jessica Noviello, a scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “We’re still trying to figure out exactly what kinds of ingredients need to go into creating life in the first place, and we know that one of the most important is water.”

[Related: NASA’s first attempt to smack an asteroid was picture perfect]

Another reason researchers are so interested in learning more about Haumea is because it’s the largest of a dozen “sibling” water-rich objects that appear to have similar orbits to each other. To date, it’s the only such “family” system in the Kuiper Belt, but scientists like Noviello say one of the area’s biggest mysteries is how this unique system came together—including its intriguing configuration. 

To try and piece together a sharper picture of the planet’s origins and evolution, Noviello and a team of researchers used computer simulations to model billions of years of its past history to see what kind of conditions may have led a “baby Haumea” to the system’s mature modern-day incarnation.

By plugging Haumea’s estimated size, mass, and rotational rate into their model, the researchers were able to use these simulations to break the planet down and build it up from scratch to investigate many of the chemical and physical processes that helped its development. Once they had all three of these aspects, they calculated the object’s angular momentum (its ability to continue to spin) throughout history with the assumption that it stayed constant. After running dozens of simulations filled with different variables and small changes to test how each variable would affect its evolution, they came up with a few results that seemed to be on the right track. 

“One of the leading ideas is that these family members were knocked off by a big collision,” says Steven Desch, a professor of earth and space exploration at Arizona State University. If pieces of Haumea were bumped due to some clumsy meet-cute with another object, there would be considerably more fragments, and many of them would have differences in their orbits. But that isn’t the case, Desch notes. Instead, their models posit that when planets were still forming, Haumea did collide with another object, but the pieces that flew off back then are not what’s seen in today’s Haumean family, as other researchers have suggested. 

The family instead came much later, when the planet’s dense rocky structure settled in the center and became its core, while lighter density ice rose to its outer layers. “The effect of having all that water percolate through the core and react with rock and turn dense rock into a less dense clay is it swells up the core,” says Desch. In effect, some of the mass on the outside of Haumea was flung off, and those pieces created the Haumean family scientists study today. 

[Related: What’s hiding in the outer solar system?]

Their model was also able to make predictions about the amount of ice on Haumea, as well as the planet’s volume. With the help of another code called IcyDwarf, researchers even concluded that at one point Haumea was warm enough to sustain a liquid water ocean in its interior for about 250 million years. Though that ocean has since frozen over, Noviello says it’s invaluable discovering what the origins of another planet might have looked like, if only to help humans discover more icy and ocean worlds in the future. 

“Knowing about the diversity of ocean worlds and their potential for life in the solar system helps us put everything into context and focus on the best targets for more extensive observations for detecting any kind of bio signatures in the future,” she says. “On Mars, the phrase is to follow the water and it’s no different with exoplanets.”

Correction (October 20, 2022): This story has been updated to correct the amount of time the Haumea spins on its axis. One of the references of Jessica Noviello‘s name was previously misspelled. We regret the error.

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Scorching heat, pillars of darkened ash, gushing lava fountains. Volcanic eruptions on Earth are paradoxes of life and death, though they are nothing compared to entire planets embalmed in such a nightmare. 

Lava worlds and other volcanically active bodies are some of the most enthralling cosmic destinations astronomers have ever discovered, and still some of the most scientifically elusive. The James Webb Space Telescope’s first batch of findings could reveal their secrets in greater detail, when paired with research already in the works. In an upcoming issue of the journal Monthly Notices of the Royal Astronomical Society, a team of scientists at Cornell University took existing atmospheric and surface composition data to understand the mantles—or the interior—of 16 different exoplanets by modeling and synthesizing them here on Earth. They were able to create and cool artificial lava from other distant locales in our universe inside the lab, no volcanic eruption required.

Given that exoplanets are difficult to reach by even our farthest traveling space probes, there have rarely been experimental studies done on these faraway worlds, says Esteban Gazel, lead author of the study and engineering professor at Cornell University who studies geochemistry and volcanology. His team’s new research is the first to provide a “library of composition” for potential exotic exoplanet surfaces—a rolodex of building blocks that exoplanet hunters can reference in their search for faraway planets and fiery space environments. In their lab, Gazel and his colleagues meticulously combined star metallicity data, thermodynamic modeling algorithms, and physical experiments to whip up their synthetic lava batches using different measurements of starting chemicals like magnesium oxide, iron oxide, and silicon dioxide. The final result were several porous igneous rocks, crystallized magma with glass and minerals you can touch without burning your limbs off.  

[Related: Volcanoes, not alien life, might explain Venus’s weird atmosphere]

Eventually, astronomers could use the team’s data from the lava experiments to interpret the inner-makings of different exoplanets. In the future this interplanetary brochure could even be used to shed light on Earth’s red-hot beginnings. “There are so many exoplanets out there in different evolutionary stages,” says Gazel. “If we can figure out their composition, it will give us a lot of information about how our planet evolved.”

Before the dawn of its glittering blue oceans and towering green forests, Earth too was a lava planet—molten and uninhabitable. At one point in its 4.5 billion-year lifetime, the planet might have resembled the hellish landscape of other super-sized Earths, like 55 Cancri e residing some 41 light years away. Today, we know that volcanoes are vital to spawning and sustaining life, as these volatile processes help with atmospheric cooling, land formation, and turning dead dirt into fertile flesh once more. 

While using other planets to investigate our hot origins is hardly a new approach, it would be natural to expect alien planets to possess foreign elements—chemical compounds or materials that we would be unable to replicate on Earth. Yet Lisa Kaltenegger, co-author of the study and the director of the Carl Sagan Institute at Cornell and associate professor in astronomy, says that isn’t the case. She explains that while they may look different to the naked eye, many planets and stars in our celestial neighborhood actually hold the same celestial ingredients, just arranged in different ways. 

“When we look at other stars, we see the disks around them that make the planets,” she says. “And so far in those disks, we haven’t found anything we can’t explain.” That means that their team was able to create all 16 synthetic surfaces with chemical materials easily found here on Earth. Kaltenegger says their work is only just beginning to create a larger picture of the cosmos, and will only continue to improve. They plan to pull in exoplanet data from the James Webb Space Telescope, which will become more precise over time.

[Related: Astronomers are already using James Webb Space Telescope data to hunt down cryptic galaxies]

Despite some calibration issues since the telescope’s initial data release, Karl Gordon, an astronomer at the Space Telescope Science Institute, says that such small setbacks are expected of any mission. The only difference this time, he says, is how quickly scientists are jumping on the data. “The best way to describe calibration is it’s an exponential,” he says. “Right at the beginning, it’s not so good, and then it quickly gets better and better.” 

Kaltenegger agrees that the calibration issues are mere “stepping stones,” that will begin to clear up as JWST’s mission continues.  

“I think the more time we have with the data, the better we’re going to be in actually finding out nuances that we don’t even see yet,” she says. 

Correction (October 5, 2022): Information in the story originally implied that the new study used data from the JWST. We updated the language to clarify that the team plans to use JWST data in future experiments. An earlier version of this story misspelled Esteban Gazel’s name. We regret the error.

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Astronomers typically divide the planets in our solar system into two types: Rocky worlds and gas giants. But, according to a new study of planets in other star systems in our galaxy, there’s a third kind of world, which is made up of about 50 percent water and 50 percent rock. And such a water-rich world is a tantalizing place for astronomers to test their hypotheses about what makes a planet capable of supporting life. 

“Within our lifetimes, we may, for the first time, be able to say something scientifically proven about habitability on other planets,” says Rafael Luque, a postdoctoral fellow at the University of Chicago who is the first author on the new study published Thursday in the journal Science. “And that’s a major, major step.”

In recent years, astronomers have been rapidly detecting new planets orbiting stars beyond our own, called exoplanets. To date, more than 5,000 exoplanets have been discovered and confirmed. But figuring out exactly what those worlds look like—and therefore whether or not they might be habitable—from light years away is a difficult feat. 

Most exoplanets have been discovered using what is called the transit method, which identifies a planet indirectly by observing how its star’s light dims slightly when the planet passes in front of it. Astronomers can also infer the radius of an exoplanet by how much starlight it blocks. Scientists have used that information to compare these alien worlds with the planets in our own solar system as a way of hypothesizing what they might look like. A planet with the same radius as Earth, for example, is thought to be quite rocky.

But in orbit around many red dwarf stars, which are by far the most common stars in our galaxy, there’s a kind of planet that doesn’t have an analog in our solar system. Based on their radii, these worlds fit in the gap in size between Earth and Neptune. 

[Related: Newly discovered exoplanet may be a ‘Super Earth’ covered in water]

The thinking among astronomers has long been that those small planets fit into two categories: some were thought to be “super-Earths” and some were “mini-Neptunes.” This idea was bolstered by the observation of a dearth of exoplanets that had a radius around 1.6 times that of Earth, which is called a “radius valley,” explains Ravi Kopparapu, a planetary scientist at NASA’s Goddard Space Flight Center who was not involved in the new study. The way that a star’s radiation erodes a planet’s atmosphere, he says, has been thought to explain that gap in radii.  

By that logic, “super Earths,” which were on the smaller side of that radius valley, were left with very thin atmospheres and a largely exposed rocky surface. “Mini-Neptunes,” on the other hand, had retained thick, puffy atmospheres and therefore these gassy planets had larger radii. 

But there could be other ways to build an exoplanet to have those radii. Because they have no analogues in our solar system, these worlds could be truly alien. So to figure out what materials might make up these distant planets, Luque and his collaborator Enric Pallé sought to determine their density.

Density isn’t something that can be measured directly from so far away, but with a planet’s mass and radius, it’s a simple calculation (mass divided by volume equals density). The researchers used the radius and mass measurements from 34 planets newly detected by the Transiting Exoplanet Survey Satellite (TESS), which launched in 2018, to gather a sample of densities for these mysterious small exoplanets.

[Related: We may be underestimating how many cold, giant planets are habitable]

Based on their calculations, the radius valley is not what separates the different types of planets in orbit around red dwarf stars. It’s density. And they extrapolated that those exoplanets can be one of three types of world: rocky, gaseous, or, the new type, water-rich. 

“We may think of Earth as a water-rich planet, but the water on Earth is just 0.02 percent of its total weight,” Luque says. The density of these distant water worlds, meanwhile, indicates that about half of their mass is water. 

But don’t start picturing a world with a rocky core and a deep ocean of water sloshing around on top of it, exposed to space, Luque says. “What we’ve seen in our sample is that this water cannot be on the surface,” he says. “The water may be trapped below the surface or maybe mixed with the magma, but it is not going to be in the form of deep, deep oceans–at least not at the surface.”

The closest analogues that we have in our own solar system to such water-rich worlds are the moons of Jupiter and Saturn. For example, Europa, one of Jupiter’s moons, has a deep ocean sloshing around under a global water ice shell. 

It’s unlikely that these exoplanets have a water ice shell, Luque says, because they are much closer to their star–any water on the surface would evaporate. That is, at least, on the sun-facing side of the planet. These worlds do not turn on their axis to have a day and night cycle like Earth does. Instead, there is a permanent light and dark side. However, Luque says, perhaps there is a region where the light and dark side meet, in a sort of a perpetual twilight, where the temperature on the surface might be just right for liquid water to be stable. 

In the search for habitable worlds, astronomers typically use liquid water as a guide. That’s because it is essential for life as we know it (that is, life on Earth, because it is the only life we know of so far). 

“We only have one template of life in this universe, so we use that as a template to find life elsewhere,” Kopparapu says. But stable liquid water isn’t the only thing needed to make a place habitable by that definition, and just because a place is capable of supporting life doesn’t mean that something lives there, he adds. 

To investigate the habitability of these distant worlds, astronomers will turn to tools like the newly-launched James Webb Space Telescope (JWST), which can peer into the chemistry of exoplanet atmospheres to reveal more details about their composition. With telescopes like JWST, astronomers will look for water vapor to confirm the presence of H2O as well as gases like methane, oxygen, carbon dioxide, nitrogen, and more that are found in Earth’s atmosphere. 

“We are finding more and more evidence that there are a lot of potentially habitable worlds. Our Earth is not unique,” Kopparapu says. He uses an analogy: “If you move into a new neighborhood, and you want to introduce yourself to your neighbors, you may see a lot of houses but you don’t see many people. So we are finding lots of houses. Now we just need to find people.”

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NASA’s James Webb Space Telescope (JWST) continues its sizzling summer of scientific discovery, finding the first clear evidence of carbon dioxide in the atmosphere of an exoplanet. The findings have been accepted for publication in the journal Nature. Extrasolar planets, or exoplanets, are any planet outside of our solar system. Most of them orbit other stars the way Earth orbits the sun, but some free-floating exoplanets (aka rogue planets) orbit a galactic center, untethered to any other stars.

This new finding means that the groundbreaking JWST may be able to detect and measure key molecules like carbon dioxide in the thinner atmospheres of smaller rocky planets in the future. This kind of data gives scientists insight into the formation, composition, and evolution of the galaxy’s planets.

Exoplanet WASP-39b was first discovered in 2011. Seven years later, NASA’s Hubble and Spitzer space telescopes detected water vapor, sodium, and potassium in WASP-39b’s atmosphere, offering a glimpse at what’s going on around the planet. In 2022, it became the first exoplanet to be studied by JWST.

Spinning about 700 light-years away from Earth, WASP-39b is a hot gas giant with a mass about the same as Saturn, but a diameter about 1.3 larger than Jupiter (our solar system’s biggest planet). The planet’s puffiness is partially due to the fact that it’s about 1,600 degrees Fahrenheit (900 degrees Celsius), giving it the nickname “hot Saturn.” WASP-39b is in an endless summer because it orbits its home star very closely, unlike the cooler and more compact gas giants in our solar system. It’s so close that it completes a complete orbit of its star, or one “year,” in just over four Earth-days.

[Related: NASA’s official exoplanet tally has passed 5,000 worlds.]

WASP-39b was first reported using ground-based detections of periodic dimming of light from its host star. This is when the light from the planet’s host star dims as the the planet passes in front of it, like during an eclipse. Transiting, or this eclipse-like event, can provide researchers with ideal opportunities to probe planetary atmospheres.

Different gases absorb different combinations of colors, which means researchers “can analyze small differences in brightness of the transmitted light across a spectrum of wavelengths to determine exactly what an atmosphere is made of” according to NASA. WASP-39b’s combination of inflated atmosphere and frequent transits makes it a perfect target for a technique called transmission spectroscopy.

The team used JWST’s Near-Infrared Spectrograph (NIRSpec) for these observations. “As soon as the data appeared on my screen, the whopping carbon dioxide feature grabbed me,” Zafar Rustamkulov, a graduate student at Johns Hopkins University and member of the JWST Transiting Exoplanet Community Early Release Science team, which undertook this investigation, said in a statement. “It was a special moment, crossing an important threshold in exoplanet sciences.”

[Related: Newly discovered exoplanet may be a ‘Super Earth’ covered in water.]

Measuring such subtle difference in the brightness of so many single colors across the 3 to 5.5-micron range in an exoplanet transmission spectrum is a first for researchers, NASA reports. It’s critical to access this part of the spectrum when measuring how much gas, water, methane, and carbon dioxide in exoplanets.

“Detecting such a clear signal of carbon dioxide on WASP-39 b bodes well for the detection of atmospheres on smaller, terrestrial-sized planets,” team leader Natalie Batalha of the University of California at Santa Cruz said in the NASA statement.

For scientists, understanding what makes up a planet’s atmosphere is important because it offers a window into its origin and evolution. “Carbon dioxide molecules are sensitive tracers of the story of planet formation,” research team member Mike Line of Arizona State University said in the NASA statement. “By measuring this carbon dioxide feature, we can determine how much solid versus how much gaseous material was used to form this gas giant planet. In the coming decade, JWST will make this measurement for a variety of planets, providing insight into the details of how planets form and the uniqueness of our own solar system.”

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An extrasolar planet named TOI-1452 b was recently discovered by an international team of researchers led by Charles Cadieux, a graduate student at the Université de Montréal and member of the Institute for Research on Exoplanets (iREx). Their findings on this possible “Super Earth” were published in The Astronomical Journal.

According to NASA, extrasolar or exoplanets are any planets beyond our solar system. Most exoplanets orbit other stars like Earth does with our sun, but free-floating exoplanets (or rogue planets) orbit the galactic center and are untethered to any star. TOI-1452 b is about 100 light-years away from planet Earth and is orbiting a red dwarf star in a binary star system located in the Draco constellation. It is slightly bigger than Earth in both in size and mass and is potentially rocky.  TOI-1452 b’s temperature is what Goldilocks would call “just right,” since liquid water could exist on its surface due to the planet’s distance from its star.

The team believes that TOI-1452 b could be an “ocean planet.” These types of moist celestial bodies are completely covered by a thick layer of water, like some of Jupiter’s moons and Saturn’s moons. According to astronomers, some of the recently identified exoplanets have a density that can only be explained if a large fraction of their mass is made up of lighter materials than the ones that make up the internal structure of the Earth. Water is the primary suspect.

“TOI-1452 b is one of the best candidates for an ocean planet that we have found to date,” Cadieux said in a statement. “Its radius and mass suggest a much lower density than what one would expect for a planet that is basically made up of metal and rock, like Earth.”

Two experts in exoplanet interior modeling (Mykhaylo Plotnykov and Diana Valencia of The University of Toronto) analyzed TOI-1452 b and their modeling shows that water may make up as much as 30 percent of the planets mass.

[Related:NASA’s official exoplanet tally has passed 5,000 worlds.]

The team first got on TOI-1452 b’s trail through NASA’s Transiting Exoplanet Survey Satellite (TESS), a space telescope that searches the entire sky for planetary systems close to our own. According to the study, the TESS signal showed a slight decrease in brightness every 11 days, leading astronomers to believe that the exoplanet is about 70 percent larger than Earth due to this quick orbit time. According to NASA, one “year” on TOI-1452 b is only 11 days, since it takes that amount of time to orbit its star. The red dwarf star is smaller and cooler than our sun, so TOI-1452 b receives about as much light as what Venus gets from the sun. Cadieux and a group of astronomers follow-up TESS observations with ground based telescopes to confirm the planet type and other characteristics.

“I’m extremely proud of this discovery because it shows the high calibre of our researchers and instrumentation,” said René Doyon, Université de Montréal Professor and Director of iREx and of the Observatoire du Mont-Mégantic (OMM) in a statement. “It is thanks to the OMM, a special instrument designed in our labs called SPIRou, and an innovative analytic method developed by our research team that we were able to detect this one-of-a-kind exoplanet.”

[Related: Some exoplanets tilt too much, and it’s pushing everyone apart.]

More follow up is needed to confirm theories on the planet’s density and status as an ocean planet. Scientists say it might also be a huge rock, with little or no atmosphere or even a rocky planet with an atmosphere made up of hydrogen and helium. TOI-1452 b is perfectly positioned for further study by the recently launched James Webb Space Telescope. It’s only 100 light-years away (fairly close in astronomical terms). Its brightness should allow Webb to capture a spectrum of starlight shining through its atmosphere. These spectrums are kind of like a fingerprint of what makes of its atmosphere. Its position in the Draco constellation is also one that Webb can observe almost any time of year.

Since exoplanets are an emerging area of discover, The International Astronomical Union is launching the NameExoWorlds 2022 Competition to give the public a chance to name christen some of the first exoplanetary systems to be seen by the Webb telescope.

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In the past decade, hunting for Earth-like exoplanets has become one of astronomy’s top priorities. Combing through billions of galaxies and star systems for signs of life is akin to searching for a needle in a haystack, but a new NASA approach aims to make them infinitely easier to spot. 

The proposed study, dubbed the Hybrid Observatory for Earth-like Exoplanets (HOEE), will establish a two-pronged observatory—both on Earth and in orbit—to create one of the most powerful planet-seekers ever designed. HOEE plans to use the next-generation of powerful telescopes currently under construction, such as the Giant Magellan Telescope and the Extremely Large Telescope (ELT) in Chile’s Atacama Desert, along with a space-based instrument called a ‘starshade,’ an object that can be used to block the light of an extremely bright object. 

At the moment, there are two ways researchers can view exoplanets directly. Scientists can take pictures using telescopes’ high-powered cameras which can be sent back through the air to Earth via radio waves to spot where a planet might be orbiting a star. For example, the Hubble Space Telescope has found hundreds of exoplanets using its digital camera. Another strategy astronomers use is a method called transit spectroscopy. When light from a nearby star travels through the atmosphere of an orbiting planet, it takes on properties of what it’s passed through. As that light reaches a telescope in space and on the ground, scientists can process  loads of data, such as atmospheric and structural information, about the environments that light has passed through. The James Webb Space Telescope used this method to make observations of the exoplanet Wasp-96. But while the JWST is capable of detecting exoplanets, its primary research objectives and design aren’t focused on searching for extraterrestrial life on far-off planets. That’s where a hybrid observatory, a two-part system that utilizes instruments both on the ground and in space, could come into play. 

[Related: NASA’s official exoplanet tally has passed 5,000 worlds]

The light of distant Earth-like planets is extremely faint, making it easy for an exoplanet’s presence to be washed out by stars as brilliant as our sun, explains John Mather, a senior astrophysicist in the Observational Cosmology Laboratory at NASA’s Goddard Space Flight Center and lead for the HOEE study. That’s not a good thing when astronomers are searching for places in the galaxy similar to our solar system. 

“The sun is 10 billion times as bright as the Earth,” says Mather. “That’s an awful lot of glare.” Searching for small objects, especially “a little Earth,” within that intense glare is extremely difficult, he says. But a starshade offers a way to block a host star’s radiance. 

Overall, a starshade is an object that would be positioned in space between a telescope on Earth and a star astronomers would like to observe, essentially blocking the light before it reached the telescope’s mirrors. A functional starshade would have to be more than 300 feet in diameter, and be positioned at least 100,000 miles away from Earth. Because it would be so far away, it would also need to be able to operate without human intervention. That said, the starshade would merely be a tool that would allow any telescope on Earth to peer generally unimpeded into the cosmos, but it’s still up in the air if one could be made to conduct any sort of science of its own. 

If deployed, this kind of hybrid observatory would allow scientists to explore corners of the Milky Way and other systems of interest much closer than existing technologies can today. Mather says a one minute exposure taken by a hybrid observatory would be long enough to prove that there’s an exoplanet in the area, and a one-hour exposure could give clues into whether there is oxygen or water in its atmosphere. 

[Related: Let’s make 2022 the year of the sunbrella]

But the technology needed to construct a starshade is still years away, Mather says. One of the biggest challenges behind the concept is just how big it would need to be to operate the way scientists would want it to. Past preliminary designs made by NASA’s Jet Propulsion Laboratory have been too big to fit into a rocket, but researchers are looking to concepts that could be compartmentalized and then opened up later, similar to JWST’s folded mirrors. “Nobody’s ever even tried something so big. It’s just enormous,” Mather says. “It’s a very big deal to put something so big into space.”

Although NASA has not pursued development, the agency has recently launched the Ultralight Starshade Structural Design Challenge, a competition that seeks to collect observatory design ideas from the public. The top five submissions will have a chance to win prizes, with first place winning $3,000. At the time of this writing there are 11 entries, but interested participants have until August 22 to submit designs. Mather, who will lead the team that will select the winner, said tapping into the public’s ideas could help push the concept of starshades off the ground. 

 “We are trying to solve some very nearly impossible problems of mechanical engineering,” he says. “On the other hand, I think it’s worth trying.”

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On Monday evening, President Joe Biden and NASA released the first complete image from the James Webb Space Telescope (JWST), heralding a new era of scientific observation. 

Tuesday morning, during the opening remarks for the JWST image releases, Webb Program Director Greg Robinson asked the audience on NASA’s Goddard Campus if anyone had seen the scene released last night. 

“Well,” he said, after people cheered enthusiastically. “You ain’t seen nothing yet.”

The JWST team has released five images from its first six months of flight and observation. The telescope is the largest and most powerful observatory released into space, and part of its strength is its ability to capture visuals through infrared light—it adds depth that the human eye can’t detect. 

The telescope is able to look through dust and clouds to see the birth of stars and galaxies more than 13.1 billion years ago, further back in time than humanity had been able to previously observe. The universe is estimated to be 13.8 billion years old, which means, as NASA Administrator Bill Nelson said Tuesday, that humans are closer than ever before to understanding what happened after the Big Bang, when the universe started. 

“We will be determining questions we don’t even know to ask,” Nelson said. 

[Related: What comes after the James Webb Space Telescope? Some astronomers want LIFE.]

The JWST images depict clusters of galaxies formed about when the sun and Earth formed, water vapor in the atmosphere of an exoplanet 1,000 light years away, the planetary nebula around a dying star, the cosmic evolution of galaxies, and the birth of stars. 

And all of this is just the beginning, said Jane Rigby, the Operations Project Scientist for the JWST. With fuel for another 20 years, the telescope is anticipated to collect data that scientists haven’t yet developed the questions for. 

Prior to this, it took Hubble two weeks to take the farthest-ever image of a galaxy. The JWST will be able to capture images even more distant in a shorter amount of time—all of these images were captured within a week. “With Webb,” Rigby said, “we did this before breakfast.”

Carina Nebula (above)

The top image sparkles with stars—including freshly made ones—in a sea of gas and dust. JWST captured part of the Carina Nebula, an area called NGC 3324, revealing new regions where infant stars are born. Visible light can’t detect the stellar nurseries, thanks to the cosmic dust in the way. But because JWST’s Near-Infrared Camera and Mid-Infrared Instrument use infrared light, the telescope can pierce through the dust, unveiling stars by the hundreds and even galaxies in the background.

Ultraviolet radiation from the young stars has carved into the wall of the nebula, creating the appearance of crags and canyons in the image, which NASA named the Cosmic Cliffs. The scene, 7,600 light-years away, is immense: Some of the pillars of dust and ionized gas are 7 light-years high.

Southern Ring Nebula

Two JWST cameras observed the Southern Ring Nebula, also known as NGC 3132. Two stars, orbiting each other, are encased in layers of gas and dust 2,500 light-years away from Earth. One of the stars is nearing the end of its life; as it dims, the sun expels cosmic debris in bowl-shaped shells.

Data from these images will help astronomers understand these type of events, known as planetary nebulae, in greater detail. The gassy puffs are final gasps in slow-motion. It takes tens of thousands of years for planetary nebulae to extinguish. In the meantime, researchers can study images like this one to understand what molecules make up the stars’ shrouds.

Wasp-96 b

Though it isn’t as flashy as some of JWST’s other images, this data reveals that water vapor is present in the atmosphere of an exoplanet—a planet outside our solar system—more than 1,000 light years away. This information will be crucial in searching for potentially habitable planets beyond Earth. WASP-96 b is just one of more than 5,000 confirmed exoplanets in the Milky Way, and is an extremely hot, gas giant planet unlike Venus or Jupiter. It is also hotter and “puffier” than any planet that orbits our sun, with a temperature pushing 1,000°F and half of Jupiter’s mass but 1.2 times more its diameter. 

On June 21, the Near-Infrared Imager and Slitless Spectrograph on JWST measured light from the WASP-96 b system for more than six hours, producing a light curve that provides more data about the makeup of the exoplanet’s atmosphere. On the chart, the peaks and valleys indicate the presence of water vapor detected in the wavelengths of light, showing evidence of haze and clouds that previous studies of WASP-96 b were unable to detect. 

Stephan’s Quintet

This mosaic, constructed from nearly 1,000 image files and more than 150 million pixels, is JWST’s biggest image yet. Five galaxies are seen here. One, named NGC 7318B, is tearing a destructive path through the cluster. JWST has captured the shock waves from its intrusion, as well as gas and dust pulled into swirls and swoops as the galaxies’ gravities interact.

Because four of the five are so close, on the cosmic scale, they provide what NASA calls a “laboratory” to study fundamental processes of galactic evolution. Here, the galaxies have disturbed each others’ gases, and have even triggered the formation of new stars in their neighbors.

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Somewhere in the universe, there may be rocky worlds perhaps twice as distant from their host stars as Earth is from the sun. So far from their stars’ warmth, these planets should be quite cold—and any water on their surfaces should be frozen. 

But planetary scientists say there could be a class of rocky exoplanets covered in thick blankets of hydrogen and helium gases. If those layers insulate the planets’ cores from the harsh chill of space, their surfaces might be just the right temperature to host liquid water. And, if that’s the case, it’s possible that these worlds are habitable.

About a decade ago, scientists proposed that such worlds might be able to support life. They sometimes refer to these planets as “cold super-Earths,” because they’re probably up to 10 times more massive than our home. But the researchers hadn’t figured out whether water could stick around on these exoplanets long enough for life to evolve. 

Now, new calculations described in a paper published Monday in the journal Nature Astronomy suggest that the surface conditions of these worlds could have been temperate for more than enough time for life—for 5 billion to 8 billion years. Earth is only about 4.5 billion years old, by comparison, and life emerged here about 3.7 billion years ago. 

“Life needs some time to evolve. So it does matter that it has been a long period,”  says Björn Benneke, a professor of astrophysics at the Institute for Research on Exoplanets at the University of Montreal who was not involved in the new study. If super-Earths only had liquid water for relatively small slices of their existence–for instance, a million years or so–it would be “discouraging” for the hypothesis that these planets may be habitable beneath hydrogen atmospheres, he says.

The new calculations bode well for the potential habitability of these cold super-Earths. Their existence is still theoretical—none have been found yet—so this adds an incentive for astrophysicists to hunt for this exoplanet class as they seek to determine whether we’re alone in the universe. 

[Related: NASA’s official exoplanet tally has passed 5,000 worlds]

“It’s important to be really open-minded, and not to expect that life has to be under conditions that are just a copy of exactly Earth,” says Marit Mol Lous, lead author on the new paper and a PhD student studying exoplanets at the University of Zurich in Switzerland. “This gives us an extra argument to keep these exotic habitats in mind.”

Based on our only model of a known-habitable world, Earth, scientists often look for a planet that also orbits its star in a region where the planet’s surface is neither too hot nor too cold for liquid water. That region is often called the habitable zone, or nicknamed the “Goldilocks zone.” So-called cold super-Earths, in contrast, lie beyond their stars’ habitable zone. But that might also, counterintuitively, be part of what makes those alien worlds habitable. 

On Earth, atmospheric greenhouse gases such as carbon dioxide and methane help maintain that “just right” temperature for water. Hydrogen can also act as a greenhouse gas, if there’s enough of the stuff around.

The trick is keeping that hydrogen gas around long enough for it to build up. It’s a particularly light element, so unless a planet is massive enough and has enough gravity to hold onto the gas, hydrogen will vanish into space.  And if the planet is close to its star, the radiation can make those particles escape more quickly. The vast distance between these cold super-Earths and their stars could protect their hydrogen gas from being torn away.

To figure out what it would take for a cold super-Earth to maintain just the right thickness of a hydrogen-helium atmosphere over an extended period of time, Mol Lous developed computer models of various sized rocky exoplanets. She placed them at multiple distances from their simulated host stars. Then, she ran a simulation of how they might evolve over time. 

Mol Lous considered factors that would affect a planet’s surface temperature such as the rate of escape, how its host star might brighten or dim over time, and the heat emanating from radioactive material in its interior. 

[Related: On this blisteringly hot metal planet, a year lasts only 8 hours]

She found that the sweet spot for long-term liquid water was if the hydrogen-helium dominated atmosphere was between 100 and 1,000 times as thick as Earth’s atmosphere, the planet’s mass was one to 10 times that of the Earth’s, and it sat at least two times as far from its star as Earth does the sun. 

That distance, while it makes these cold super-Earths intriguing to study, it also makes them extremely difficult for astronomers to spot. The technique that scientists usually use to detect an exoplanet relies on the world passing in front of its star. Such a transit makes the host star’s light dim slightly, which astrophysicists use to calculate the presence of an orbiting world. But, says Benneke, when a super-Earth-sized planet is orbiting so far out, it is much less likely to be aligned at the right moment to be detectable with current technology. 

As such, it’s still unknown whether such super-Earths exist, he says. “But … what experts have shown is that this kind of diversity of planets, the whole range of planets that can exist is actually extremely big.” And if they do exist, many questions remain about how such a chilly, wet world might come to be. Mol Lous and her colleagues are already working on new models to explore the formation of cold super-Earths. 

But the best solution to these mysteries, Benneke says, “would be to simply find these exoplanets.”

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NASA has officially confirmed the existence of more than 5,000 exoplanets—planets that exist outside our solar system—as of Monday. A new batch of 65 confirmations pushed the tally up to 5,005 on the agency’s Exoplanet Archive. 

The 5,000-plus alien worlds are diverse. Some are small and rocky. Others are gas giants that dwarf Jupiter. Some exoplanets orbit two stars at once, while others orbit long-dead stars. So far, the confirmed exoplanets break down into: 30 percent gas giants, 35 percent Neptune-like dark and icy worlds, and 31 percent super-Earths (planets up to 10 times Earth’s mass but smaller than Neptune’s). Just 4 percent are rocky planets comparable in size to Earth or Mars. Confirming 5,000 of these planets is remarkable, but it’s only the start. There are likely hundreds of billions of exoplanets in our galaxy, the Milky Way, alone.

Five thousand is “not just a number,” Jessie Christiansen, science lead for the exoplanet archive and a research scientist with the NASA Exoplanet Science Institute at Caltech in Pasadena, said in NASA’s announcement. “Each one of them is a new world, a brand-new planet. I get excited about every one because we don’t know anything about them.”

Exoplanet discovery was, for a while, limited by the technology we have on Earth—we can only peer so far into the cosmos from our own rocky planet, and Earth’s atmosphere can interfere with readings. The advent of telescopes launched into space dramatically increased our exoplanet detection capabilities. And with even greater advancements in science, and new observatories like the James Webb Space Telescope, even more exoplanet discoveries are almost inevitable. 

“Of the 5,000 exoplanets known, 4,900 are located within a few thousand light-years of us,” Christiansen said in a Q&A with Caltech. “And think about the fact that we’re 30,000 light-years from the center of the galaxy; if you extrapolate from the little bubble around us, that means there are many more planets in our galaxy we haven’t found yet, as many as 100 [billion] to 200 billion. It’s mind-blowing.”

[Related: On this blisteringly hot metal planet, a year lasts only 8 hours]

Astronomers have been pinpointing exoplanets since 1992, when radio astronomers Aleksander Wolszczan and Dale Frail announced the discovery of two planets orbiting a pulsar, a rapidly spinning neutron star that pulses with radiation signals. They published their findings in Nature. 

Exoplanet research since then has boomed, especially after the Kepler space telescope launched in 2009. During its 9 years in operation, Kepler helped scientists rack up 2,700 exoplanet discoveries—and astronomers are still parsing its immense logs and readings to see if they missed any planets hiding in the mounds of data.

“Now, exoplanets are almost ordinary,” Christiansen told Caltech. “My colleague David Ciardi [chief scientist for the NASA Exoplanet Archive] pointed out the other day that half of the people alive have never lived in a world where we didn’t know about exoplanets.”

But there’s still much more to learn and discover, Christiansen said. “Now that we have enough planets, we can really slice and dice and ask how different kinds of planets are made,” or how the different ages of stars affect their orbiting planets. “The more planets we have,” she added, “the more answers we have.”

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The molten cores of larger rocky exoplanets should stay hot longer than those within small worlds, according to a study published Thursday in the journal Science. That’s good news for interstellar explorers–because a molten core is probably required for life to develop on a planet.

Determining this feature of exoplanets required an experiment with giant lasers and an incredibly thin sliver of iron placed under unprecedented pressure. “We’re finding so many planets, and [one of] the big questions people have are: are these planets potentially habitable?” says Rick Kraus, a physicist at Lawrence Livermore National Laboratory who led the study.

To answer this question, researchers don’t normally start with thinking about a planet’s core. Instead, they ask whether the planet is the right distance from its star or whether it has water. But Kraus and his team wanted to find other ways to discern whether a planet is habitable.

They explored a planet’s ability to form a magnetosphere—a magnetic field that protects it from solar radiation, like the one around Earth does for us—as a window into habitability, Kraus says. Life as we know it wouldn’t be possible without the Earth’s magnetic field.

Magnetic fields are a result of molten planetary cores. Earth has a core composed mostly of iron, split into a solid inner core and a liquid outer core. Earth’s magnetic field is caused by the convection of the liquid iron, meaning how it swirls: The cooler, denser liquid areas sink to the bottom, while the hotter ones rise like wax in a lava lamp.

Studying an exoplanet’s core in a laboratory is difficult because there are few ways to recreate such intense pressures and temperatures. This is the first experiment to measure iron’s melting temperature at pressures exceeding those in Earth’s core, Kraus says. To achieve these extremes, the team needed some big lasers, specifically the National Ignition Facility in Lawrence Livermore National Lab–where big lasers are their specialty.

In the experiment, those lasers blasted a multilayered sample of iron. Layers of beryllium, a metal element, and some filters formed the outside of a super-thin iron “sandwich” while a piece of transparent lithium fluoride made up the other half, Kraus says. The outer beryllium layer heated up thousands of degrees in “a fraction of a billionth of a second,” he says, and that side of the sandwich cooked into a plasma. The plasma then expanded, driving an intense shockwave into the sample.

[Related: Saturn has a slushy core and rings that wiggle]

This process emulates the conditions that a section of hot iron would experience as it descends through a planet’s molten core. “You’re shocking the hell out of it,” says Peter Driscoll, geophysicist at Carnegie Science who models the core of Earth and other planets and was not involved in the study, who adds this was a difficult process to study. It destroys the sample, so the experimenters have to collect their data in one go. The process only produced “a couple of data points,” he says, but “these kinds of experiments are very valuable.”

As the sample reached peak pressures, another instrument tested whether that iron remained solid or liquid at key times, to help researchers home in on iron’s behavior at these high pressures and temperatures.

The team found that “as you increase the pressure, the temperature increases, quite rapidly,” Kraus says. For exoplanets, that means the larger they get, the longer it will take their cores to solidify. The super-Earths that are between four and six times Earth’s mass would take the longest, he says. The team estimates that it will take a total of 6 billion years for Earth’s core to solidify, whereas cores in large exoplanets of similar composition to Earth should take up to 30 percent longer. 

“While that may sound sort of intuitive,” it wasn’t a given with all the different factors, Kraus says.

Measuring how iron melts in extreme conditions is so important because it tells you if and how a planet’s core will solidify, Driscoll says. Even at the boundary between Earth’s solid inner core and liquid outer core, scientists don’t know precisely what the temperature is–though it’s estimated to be near that of the sun’s surface, at roughly 10,000°F.

One issue with extrapolating these results to exoplanets is that those super-Earths can contain elements other than iron in their core, which would change their melting temperature by an unknown amount, Driscoll says. It will also be hard to predict how exoplanets cool because the mantle, the layer of hot rock surrounding the core, plays a huge role in how quickly the core can cool. And those exoplanet mantles could be made of “pretty much anything,” he says.

Venus, Driscoll says, is the go-to example of this disconnect. On paper its composition is very similar to Earth’s, but it lacks a magnetic field and plate tectonics.

Other factors can decide whether a magnetosphere will form, too, such as how well the material in the core lets heat or electricity flow through it. But these characteristics are difficult to measure, even on Earth–scientists have only succeeded in measuring the flow of heat through Earth’s core in the last decade. Still, Driscoll says, that would be, “the next thing to go after.”

Correction January 21, 2022: This article previously stated this experiment was the first to use iron at pressures exceeding Earth’s core. In fact, it was the first to measure iron’s melting point at those pressures.

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Astronomers may have found at least 70—and possibly as many as 170—new free-floating exoplanets, which are planets outside our solar system that are not tethered to any stars. The new collection of these candidates, also called rogue exoplanets, roughly doubles the known catalogue of such worlds.

The Kepler Space Telescope, which has helped astronomers confirm almost 3,000 exoplanets, retired in 2018. But the trove of data it collected during its nine-year tenure in space still holds secrets for astronomers to uncover, such as these new exoplanet candidates. Rogue exoplanets are exceptionally hard to detect because they do not have the benefit of a nearby star to illuminate them. Researchers circumvented that obstacle by looking for young planets, just a few million years old, that were still hot enough to glow. Their findings were published in Nature Astronomy. 

“We measured the tiny motions, the colors and luminosities of tens of millions of sources in a large area of the sky,” Núria Miret-Roig, an astronomer at the Laboratoire d’Astrophysique de Bordeaux in France and the University of Vienna in Austria, and the first author of the new study, said in a statement. “These measurements allowed us to securely identify the faintest objects in this region, the rogue planets.”

Most confirmed exoplanets orbit a star, which astronomers typically detect first. They can observe the exoplanet thanks to that sun’s proximate glow– more specifically, the period of darkness that results when the planet passes between the star and an observing telescope. 

Star-less exoplanets cannot be found this way. Researchers instead typically rely on a similar technique, known as “gravitational microlensing.” Astronomers find rogue planets by seeing where the light of distant stars bends in space—that distortion can reveal where free-floating exoplanets are hiding in the dark. Unfortunately, microlensing events tend to be one-off, which means astronomers are likely to never see the rogue planet again–a huge limitation when looking for these worlds.

[Related: On this blisteringly hot metal planet, a year lasts only 8 hours]

But looking for young, hot planets, as Miret-Roig and her team did, allows new candidate exoplanets to be observable in the future, providing the potential for future study. And there are many to follow up on. They identified as many as 3,455 total exoplanet candidates—70 to 170 of which are Jupiter-size objects and likely true rogue exoplanets. They are all floating in space about 420 light years away, in a region of the Milky Way known as the Upper Scorpius OB stellar association.

“We did not know how many to expect and are excited to have found so many,” Miret-Roig said in a statement. 

The team is planning a follow-up study to measure the precise age and mass of these presumed free-floaters, as well as spectroscopic observations to “determine other physical properties such as the effective temperature and the composition,” Miret-Roig told Gizmodo. With these future studies, astronomers may be able to tease apart how starless planets form in space. 

The new findings suggest there are many more of these hidden, rogue planets floating in the dark to discover, Hervé Bouy, an astronomer at the Laboratoire d’Astrophysique de Bordeaux in France, and project leader of the new research, said in a statement. “There could be several billions of these free-floating giant planets roaming freely in the Milky Way without a host star.”

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Since 1992, astronomers have discovered nearly 5,000 exoplanets and estimate that our galaxy alone has billions and billions (and billions) more. Given those stats, it’s nice to imagine that light-years away, another orb like Earth might exist, awaiting discovery by enterprising humans. It could house continents to step foot on, a reasonable atmosphere to breathe, water to guzzle, resources to extract, and food to be foraged. Blessed as our exploratory spirit will one day surely be with warp drive.

This hypothetical planet has a name: Planet B. As in, Plan B. The proverbial Planet B functions as a sort of escape hatch, real or philosophical, for when things get hairy here on Planet A. This terrestrial cousin has long shown up in science fiction, shaping how Earthlings conceive of such a place, sometimes subconsciously. “We don’t even think about the fact that something like Star Wars takes place on exoplanets,” says Lisa Messeri, a Yale anthropologist and author of the book Placing Outer Space. A New Hope, after all, preceded the discovery of any actual exoplanets by 15 years. 

There’s a big gap, however, between the scant worldmaking of the scientist, and the vivid imagination of the public. Real planets’ details remain fuzzy, with telescopes only able to determine their size, mass, distance from a star, rough temperature, and—in certain conditions—some molecules floating in their atmospheres. Scientists aren’t sure how many Planet B candidates there might be, or if any of those are truly Earth-like at all.

The James Webb Space Telescope, launching December 24, will help stitch that gap (a little), its big mirror and instruments bringing sharper focus to far-off places. But in the public imagination, planets may always have more personality and promise than we can scientifically discern, in part because of science fiction’s long history of developing their characters.

Planets have long appeared as the endpoints of “extraordinary voyages.” As early as the 16th century, “we were ‘discovering’ what was called the New World, and all of this flora and fauna, and descriptions and all of this cool stuff was being brought back to Europe,” says Ana Klimchynskaya, a scholar of science fiction at the University of Chicago. By the 18th century, writers had begun extrapolating that novelty beyond the atmosphere, to different planets where Earth-people could live. In the politically and socially experimental thought around the Age of Enlightenment, they imagined ways humans’ lives might be different: Other worlds became vessels for political satire and blue-sky what-ifs. “What other ways can we build a society?” Klimchynskaya says. “What might a utopia look like?” 

That form of writing was a type of proto-science-fiction. True sci-fi, as we think of it today, only started in the 19th century, as science itself became popular with the public, countries grew industrialized, evolution became a widely accepted thing, and we learned Planet Earth was pretty old and used to have dinosaurs. Scientifically rigorous speculation seeped into literature. It produced, says Klimchynskaya, “this new storytelling form that was based on a new sense of humanity’s power over the world.” And other worlds.

In the early to mid 20th century and to this day, many fictional planets are only sort of Earth-like, though. They’re what science fiction scholar Katherine Buse of the University of Chicago calls “nonecological:” encompassing only an aspect or two of a real world. A globe made only of rubber, a desert planet, or one populated only by women. Writers didn’t gin up these characteristics for a physical, technical reason. The planets, like those at the end of extraordinary voyages, existed to house speculation. 

A shift in literary possibilities occurred, says Buse, when author Harry Clement Stubbs, whose nom de plume was Hal Clement, published Mission of Gravity in 1954. In this serialized novel, he imagines a planet where gravity is up to 700 times stronger than Earth’s. It’s cold, fast-spinning, full of liquid methane. Aliens adapted to those conditions. The plot revolves around characters’ attempts to understand weather, geology, the atmosphere, and gravity. Rational investigations get them out of proverbial hot water. “The answer is always some kind of bringing together different scientific disciplines,” says Buse. 

Stubb’s work also demonstrated how to bake a from-scratch planet and have readers experience it as a whole world. His work, and fiction that followed, gave humans the sense that ours is not the only globe out there, and that others could be survivable, even if not totally Earthy, with the tools of science. 

Visual science fiction, though, has arguably had a stronger influence on how the average person thinks of what “an Earth-like exoplanet” might mean. Worlds in, say, Star Trek infuse us with ideas about exoplanets’ appearances, the visuals seeping subconsciously into societal conceptions. 

But the resulting visions are pretty arbitrary. Treky worlds, for instance, tend to look like the area around Los Angeles, but not because exoplanets likely resemble our tech hub. “They had no budget, so they just went outside,” says Klimchynskaya. Stargate, meanwhile, was filmed in British Columbia, so all the planets look Vancouverish.

The number of North American-style orbs in the public imagination is also misleading. “People watch Star Trek, and they’re like, ‘The galaxy must be littered with habitable planets,’” says Kaitlin Rasmussen, a University of Michigan astronomer who researches exoplanets. 

That litter feels particularly shiny now, as Earth confronts existential issues, from climate change to nuclear weapons. “It’s especially appealing to face that there’s another world that people haven’t completely messed up,” says Rasmussen. The very idea of such a world can function as a philosophical Planet B anyway—an escapist fantasy, if not an escape plan.

But “littered” might not be the right word for the density of nonfictional Planets B. “The reality is that we just don’t know,” says Rasmussen. “We haven’t found any Earth-like planets in the solar neighborhood yet. It’s possible that we could, but the range and the lifespan of habitability—it’s just so narrow.”

That scarcity is easy to forget, or never know, when news articles regularly tout the discoveries of “Earth-sized” planets or those in the “habitable zone.” Those terms sound a lot like “actually akin to Earth” and “actually habitable”—you know, like in the movies. But astronomers simply mean the planet is a non-gaseous world where liquid water could exist. 

That’s a pretty empty Tinder profile to swipe right on. Planets’ dating faces also don’t show anything close to a clear picture—more like a photo taken in a dark club, with a bunch of neon backlighting. 

Scientists can discern basics like how wide, how massive, how far from a star, and so how-ish hot or cold a globe is. And with today’s instruments, like Hubble or the European Southern Observatory’s 3.6-meter telescope and its High Accuracy Radial velocity Planet Searcher, they can determine how abundant certain atmospheric molecules are…but only for large planets close to their stars.

When a world passes in front of its star, from Earth’s point of view, it blocks a small amount of its sun’s light—like a mosquito flying in front of your camp lantern. (That blockage is often what reveals its existence in the first place.) The glimmers of starlight that pass through the planet’s atmosphere, and the signatures in that filtered light, can reveal what’s inside the atmosphere. Larger orbs orbiting close-in block and filter their stars’ light more, ratio-wise, making them easier to discern. “Over the next 10 years, we will start to move towards smaller planets that are still too hot to be in the habitable zone,” says Rasmussen. That’s all still a loud shout from being able to tell what those planets are truly like, and whether they have characteristics for life. 

Still, sci-fi enthusiasts aren’t the only ones interested in imagining, and finding, Earth-like orbs. Astronomers are motivated not so much by the hunt for an escape hatch but by the potential to understand how our planet fits, and so how we fit, into the broader universe. 

Different people grapple with that existential “hmm” in different ways. A religious person might turn to scripture, a philosopher to axioms. For an astronomer, the question morphs: “‘Are we like anywhere else in the universe?’” says Messeri. The answer requires finding out whether Earth is unique, common, or somewhere in between—to understand whether we and the conditions that keep us and the biosphere going might be unique, common, or somewhere in between. 

Her research has revealed another emotion behind scientists’ interest in Earth-twins, one not totally unlike the philosophical escape hatch: a sort of nostalgia. “A fantasy of Earth that might have been otherwise, an Earth that is pristine, an Earth that is not bothered by politics,” Messeri says. Exoplanets, particularly in their current data-deprived form, are blank slates. Onto their purely hypothetical continents, humans can project the most platonic version of this planet.

In that way, the scientist’s quest for and the public conception of the could-be Planets B are motivated by a preoccupation with what’s right here, right now. “When we’re thinking about other planets, we’re actually always already thinking about Earth,” says sci-fi scholar Buse.

With JWST, scientists are one thrust closer to finding a place like this one. Its big-mirror energy will help astronomers see smaller worlds farther away. “It can collect more light, which can give us a clearer signal,” says Caprice Phillips, a graduate student at The Ohio State University who studies whether JWST might be able to detect biosignatures from “gas dwarf” planets larger than Earth but smaller than Neptune. JWST also sees a wide range of wavelengths of light, reaching much farther into the infrared than Hubble did, but also keeping an eye on some visible wavelengths, unlike the infrared-only Spitzer Space Telescope. That’s not just longer than the wavelengths your eye can pick up, it’s also where chemicals like ammonia—which biological activity can produce, when microbes split apart hydrogen and nitrogen—spit out more signals.

But even if JWST, or a future telescope, finds a promising sign of potential biology—like ammonia in an atmosphere, which is Phillips’s speciality—the work is just starting. “You can’t just jump right away and say, ‘We found life. It exists,’” she says. Follow-up observations need to reaffirm that the signature showed up at all. And other processes, like volcanic or solar activity, can also cause that chemistry, so astronomers have to separate out possibilities—an ambiguous process, especially since astronauts can’t just rocket there and go see what’s up.

Phillips and other astronomers use a software tool called Pandexo to estimate what JWST might be able to reveal about real planets’ atmospheres. When they input the characteristics of an exo-solar system—like the star’s temperature, the planet’s radius, and how many times the telescope will watch the planet pass in front of its star—Pandexo spits out simulated data from the telescope, showing what scientists think the beryllium mirrors might be able to see. “It’ll be even cooler when we actually see what the data looks like,” Phillips says. The real world, after all, rarely reflects fictional predictions perfectly—even those that pop out of software. 

Astronomers are interested in that real data from, in part, promising solar systems like TRAPPIST-1, which has seven Earth-sized planets, three of which sit in the habitable zone. But getting a clear portrait of those places isn’t a tomorrow-type goal. “We may be a little ways off from that,” says Phillips. “But keep it in the back of your mind.”

Patience is required because humans’ ability to see exoplanets—at all—is new. “It’s a very budding field, and there’s so many unknowns,” says Phillips. JWST and follow-on instruments might, and probably will, debunk some surprising things humans thought they knew about planets and their atmospheres. To scientists like Phillips, that’s a sort of extraordinary voyage of its own. “Into the unknown,” she says. “Always.”

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Astronomers have discovered a massive exoplanet orbiting around the binary star system b Centauri. The two stars are so hot and huge that researchers previously thought that no planet could exist around them. 

B Centauri sits in the Centaurus constellation, some 325 light-years outside of our solar system. Its main star is more than three times hotter than our sun, and its two stars have a combined weight of roughly 6 to 10 suns. Until now, no planet has been found orbiting stars more than three  times our sun’s mass. The new exoplanet, b Centauri b, is also a whopper—it probably has a similar gaseous composition to Jupiter, but it’s at least 10 times more massive. It’s one of the biggest exoplanets ever discovered. And with a distance of 52 billion miles separating b Centauri b from its stars, it has one of the widest orbits ever detected. Astronomers captured images of the planet using the European Southern Observatory’s Very Large Telescope in Chile, and the findings were published in Nature on Wednesday. 

“Finding a planet around b Centauri was very exciting since it completely changes the picture about massive stars as planet hosts,” lead study author Markus Janson, an astronomer at Stockholm University, Sweden, said in a statement.

The stars of b Centauri are relatively very young—just 15 million years old, compared to our sun’s 4.6 billion years. “The planet in b Centauri is an alien world in an environment that is completely different from what we experience here on Earth and in our solar system,” co-author Gayathri Viswanath, a PhD student at Stockholm University, said in a statement. “It’s a harsh environment, dominated by extreme radiation, where everything is on a gigantic scale: the stars are bigger, the planet is bigger, the distances are bigger.”

[Related: On this blisteringly hot metal planet, a year lasts only 8 hours]

B Centauri now has planetary scientists rethinking the parameters around planet formation—the binary stars’ combined size and heat, and the tremendous amount of radiation they must emit, should create an environment inhospitable to planets. “It poses quite a challenge to our models,” Michael Meyer, a University of Michigan astronomer and co-author of the new study, said in another statement. “But this is what makes it exciting—when you are proven wrong, you learn something.”

Astronomers have yet to figure out how b Centauri b came to be, and will now be working to untangle this unlikely system’s origin story, a “mystery at the moment” that will be “an intriguing task to try to figure out,” Janson said in a statement.

Since 1992, scientists have confirmed the existence of thousands of exoplanets, revealing the often surprising diversity of conditions where planets can form. “It seems that no matter where we look—around small or big stars, single stars or binary stars, alive stars or dead stellar remnants—we always find planets in some form,” Janson told Gizmodo, “even in places we didn’t think possible.”

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A team of astronomers used data from the Transiting Exoplanet Survey Satellite (TESS) to find an exoplanet so close to its star, its surface could be molten. This “ultrashort-period” planet has a tight orbit, with a year lasting only eight hours—alien birthday parties there would accumulate so fast they’d get very tedious.

The exoplanet, called GJ 367b, is three-quarters the width of Earth, falling into the elusive category of sub-Earth. Earth-size and smaller exoplanets are difficult to detect. The go-to methods of exoplanet detection rely on measuring how much light a planet blocks while crossing its host star, or looking at how the star wobbles as the planet orbits it. Both of these features are harder to spot for smaller, lighter planets. GJ 367b is one in only a handful that have been so closely characterized.

Among these tiny worlds, “our planet is probably one of the only ones that have a precise mass and radius [measurement],” which the team could use to guess at the planet’s interior, says Kristine Lam, an exoplanet astronomer at the German Aerospace Center and lead of the study, published today in the journal Science.

The abundance of would-be birthdays on GJ 367b probably won’t be an issue, in reality, because the sun-facing surface of the planet is more than 2600°F. That’s close to the temperature at which “metal will start to melt,” Lam says.

GJ 367b is a unique planet, unlike anything scientists have observed before, says Mercedes López-Morales, an astrophysicist at the Center for Astrophysics | Harvard & Smithsonian who specializes in exoplanets and was not involved in the study. The team’s detection is solid, too, she says.

The team determined the size of the planet with TESS, and then used a ground-based instrument at the European Southern Observatory called HARPS to measure the mass of the planet by looking at the star’s “wobble.”

Credit: The Vega Astronomical Association/Nándor Dénes and Gabriella Balogh

For a typical star and exoplanet, these instruments wouldn’t have the precision to measure a sub-Earth exoplanet. But in this case, the scientists got lucky; the host star is a red dwarf that is bright and small relative to other stars. Both these attributes help the exoplanet’s signal stand out, Lam says.

The team estimated the planet’s density from its radius and mass. Astronomers can’t directly measure a planet’s core from this distance, but they can use models to infer what layers probably make it up. The team thinks the interior cross-section of GJ 367b is likely about 86 percent iron. That’s similar to Mercury in our solar system, which is about 83 percent iron, Lam says. Though this planet, because it’s about ten the mass of Mercury, is its own beast, López-Morales points out.

[Related: Why aren’t there more super Earth-sized exoplanets? Astronomers think they’ve figured it out.]

Lam plans to apply for time on the James Webb Space Telescope to investigate what kind of atmosphere the planet has–if it has one at all. The planet’s original atmosphere should be long gone, but it’s possible that vaporized elements on its hot surface form a secondary atmosphere, López-Morales says.

Scientists don’t have enough evidence to be confident how a planet like GJ 367b formed. López-Morales says she thinks it’s unlikely the planet formed so close to its star, because this region usually lacks enough material for a planet to form. 

It could have originally been Earth-like but had its rocky mantle blown apart by a massive impact–perhaps involving two smaller planets that scattered their mantles and merged into one, López-Morales says. Or it could be a remnant of a much larger gaseous planet that was whittled away by the star’s rays.

But the argument that the planet couldn’t have formed that close to the star is based on certain planet-formation models, not direct evidence, says Li Zeng, a researcher studying exoplanets at Harvard’s Department of Earth and Planetary Sciences, who was not involved in the study. “The frank answer is, we don’t know.”

If the planet used to be a gas giant, wherever it formed, that could drastically change how scientists understand the structure of gaseous planets because it “gives you a hint that gas giants actually have heavy element cores,” López-Morales says.

Correction, 12/3/2021: A previous version of this story named the institution where López-Morales works as Harvard & Smithsonian Center for Astrophysics. The center is, in fact, now called the Center for Astrophysics | Harvard & Smithsonian. 

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The James Webb telescope’s launch has been delayed till at least December 22 after a clamp fastening it to its ride malfunctioned. But when the spacecraft finally gets to orbit, exoplanet astronomers look forward to a game-changing view of exoplanets.

One in two sun-like stars in our galaxy has a sub-Neptune exoplanet, a world between the size of Earth and Neptune, says Jacob Bean, an exoplanet astronomer at the University of Chicago and co-leader of two planned exoplanet observations outlined in a recent NASA announcement. Astronomers still know little about the formation and composition of these plentiful worlds. Are they rocky Earth-like planets that grew a little larger and acquired a thick atmosphere? Or are they composed of ice like Neptune?

Most exoplanet experts hypothesize that these worlds are rocky, Bean says. And if that’s the case, the planets are also important for understanding how Earth-like planets form.

“If you want to understand anything about planets, you have to at least understand the most common type of planet,” meaning sub-Neptunes, says Björn Benneke, an astrophysicist specializing in exoplanets at the University of Montreal. Benneke isn’t involved with Bean’s team but will work on other Webb exoplanet observations. He previously found evidence there may be water on at least one sub-Neptune exoplanet.

But even the composition of sub-Neptunes’ atmospheres is tricky to observe because they’re often obscured by haze or clouds.

[Related: A newly discovered planet orbiting a dead star offers a glimpse of Earth’s future]

Such features are thought to be common in many planets’ skies. In fact, all the atmospheres in our solar system contain clouds or haze. Those are two different ways that aerosols—tiny specks of liquid or solid matter—manifest in the atmosphere, Bean says. A cloud forms when something that’s normally a gas in the atmosphere “condenses out”—a phenomenon when a gas such as water, which is typically in the air as vapor, condenses into clouds if the air is saturated. A haze is similar to clouds, Bean says, but occurs when ultraviolet radiation from a star splits up molecules in the atmosphere which makes them condense out when they wouldn’t otherwise. 

This planetary haze is different from a pollution-caused haze on Earth. A go-to example of a nearby hazy atmosphere is the one covering Saturn’s moon Titan, where nitrogen and methane in the atmosphere are broken up by sunlight and form aerosols.

James Webb can see into “mid-infrared” wavelengths that are longer than what other space telescopes see. This will allow astronomers to see deeper into planetary atmospheres because when viewed at longer wavelengths, clouds and haze are generally more transparent, Benneke says. The Spitzer Space Telescope specialized in infrared and was also a powerful tool for exoplanet astronomy, he says. James Webb is the successor to the Hubble Space Telescope, the first and most iconic large space telescope that has taken a vast trove of images over three decades in service. The Webb will be larger and more precise than both of them.

[Related: After 20 years, NASA finally finished building the James Webb Space Telescope]

Webb’s infrared view will also be able to precisely measure the temperature of exoplanets such as GJ 1214 b—one of the oldest known, most thoroughly studied exoplanets, Bean says. GJ 1214 b is easier to see because of its large size relative to its parent star, which is a red dwarf and is only 40 light-years away.

The team hopes to be able to directly measure what kind of molecules are present in its atmosphere, Bean says. But even if they can’t, because the planet is tidally locked, with one side always facing its star, the team should be able to learn about its composition with a different approach: They can take the planet’s temperature and study how the atmosphere transfers heat from the day to the night side through the super rotating jet—an equatorial jet stream that flows around the planet.

Most of the sub-Neptunes that are easy to explore are close to their stars, which makes their existence even harder to explain. They retain thick gaseous atmospheres, which should be very difficult for a small planet to hold onto with the intense solar winds and heat that close to a star. “How in the heck could these planets pull in so much [gas]?” Bean says.

Because sub-Neptunes are “at the borderline” of what Hubble could detect, James Webb could be a “complete game-changer” for studying them, Benneke says. Webb’s large size, gold-plated mirrors, and the fact that it’s kept very cold, mean it “was really built to take the temperature of the universe.”

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For the first time, astronomers have detected evidence of a planet in a galaxy beyond our own. The yet unnamed exoplanet lies in the Messier 51, often referred to as the “Whirlpool” galaxy, around 28 million light-years from Earth.

Astronomers and planetary scientists have discovered nearly 5,000 exoplanets so far, but all were found within the confines of our own Milky Way galaxy. The new discovery is the first to detect and place a planetary body in an entirely different galaxy—a feat achieved by using NASA’s Chandra X-ray Observatory telescope to observe “transit,” when a planet passes in front of a star and blocks its rays. The findings were published this week in Nature Astronomy. 

“We are trying to open up a whole new arena for finding other worlds by searching for planet candidates at X-ray wavelengths, a strategy that makes it possible to discover them in other galaxies,” Rosanne Di Stefano, Harvard University astrophysicist and leader of the study, said in a NASA statement.

Most exoplanets have been found in transit by observing dips in optical light as a planet passes in front of a star, but Di Stefano and her team instead looked for dips in x-rays. Regions where x-rays can be detected are small but bright, and this technique could allow astronomers to find exoplanets at much greater distances than with current optical light transit studies.

[Related: A newly discovered planet orbiting a dead star offers a glimpse of Earth’s future]

Though an exciting find, scientists still need to confirm the evidence—a process that, in this case, will take decades. The potential new planet won’t cross in front of its star for another 70 years, giving astronomers a long and undetermined wait before they can confirm the findings.

“Unfortunately to confirm that we’re seeing a planet we would likely have to wait decades to see another transit,” said co-author Nia Imara, a University of California at Santa Cruz astrophysicist, in the NASA statement. “And because of the uncertainties about how long it takes to orbit, we wouldn’t know exactly when to look.”

That uncertainty with timing has other planetary scientists wondering how useful this method of detecting x-ray transits is and how often it should be used. Bruce Macintosh, a Stanford University astrophysicist who wasn’t involved with the research, told NBC that studying X-ray transits is “clever,” but since “you can only see transits when objects line up just right between you and the thing you’re looking at” (and those alignments only ever last a couple hours at most) it’s unlikely that it could be used to find hundreds of thousands of planetary candidates.

But Di Stefano told NBC that she’s excited that this new method, which she and her colleagues first proposed in 2018, yielded such exciting results in the search for extragalactic exoplanets. “We did not know whether we would find anything, and we were extremely lucky to have found something,” she said. “Now we hope other groups around the world study more data and make even more discoveries.”

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A team of astronomers found the remains of a dead star, known as a white dwarf, with a surviving exoplanet that resembles Jupiter.

The team used a technique called microlensing, in which astronomers wait for two stars to line up perfectly as viewed from Earth and watch to see how the light from the distant star is bent by the gravitational pull of the closer one.

White dwarfs are small stars that are slowly cooling off because they no longer burn nuclear fuel. As they near death, stars like our Sun will expand into a red giant, then eject their outer layers leaving only a small, dense core: the white dwarf. This remnant represents “what we think will happen to our solar system in about eight billion years,” says Joshua Blackman, an astronomer at the University of Tasmania who led the study. The findings were published in the journal Nature.

As the sun grows into a red giant it will “obliterate Mercury and Venus and quite possibly earth as well on the way,” before it shrinks to a white dwarf, Blackman says.

Microlensing requires looking at how light that passed a star has been distorted. In looking at how a star changed the passing light, astronomers can figure out “the geometry of the system,” learning about the mass of a star and potentially the exoplanets that orbit it, Blackman says.

It is an indirect way to make a measurement, but “the team did a very thorough analysis” and the study was convincing, says Dániel Apai, an astronomer and planetary scientist at the University of Arizona, who was not involved with the study. Apai heads NASA’s Alien Earths project for exoplanet study.

The microlensing, which took place in 2010, required a network of telescopes, and though that data told the team about the mass of the star and its exoplanet, it didn’t provide a direct picture. So, the team followed up years later with the Keck Observatory in Hawaii—which houses one of the largest optical telescopes in the world—to try and observe the star itself. The team had to wait until the conjunction (which had allowed the microlensing) was over and the two stars got far enough apart in the sky so they could get a clear look at each, which would sort out how bright and how big they are.

From the microlensing data, the team got “a very strong indication that there’s about a Jupiter mass planet there with a star,” Blackman says. But perplexingly, using the Keck Observatory, they couldn’t spot the star.

The telescope should have been powerful enough to see any typical star at that distance. Eventually, they realized that the fact that they couldn’t detect the star wasn’t a failure in the equipment—it meant that the star was simply too dim to see. That left only a few explanations.

“It could either be a white dwarf,…a black hole, or a neutron star,” Blackman says. But the microlensing observation showed the object should be less than the mass of our Sun, and there’s no known way for a black hole or neutron star to form that small, so a white dwarf was by far the best explanation, he says.

In the future, the team hopes to observe the white dwarf directly with the Hubble or James Webb Space Telescope, Blackman says, both of which “see deep enough into the sky that we will be able to directly look at the light from the white dwarf.”

But why is spotting a planet around a white dwarf special?

First, it’s rare. This is the first time microlensing has been used to find a white dwarf and only the fifth white dwarf ever to be found with an exoplanet, according to Blackman.

And as a window into our future, none of the other white dwarfs make for a convincing solar stand-in. Two of the exoplanets are very close to their white dwarfs—only a fraction of the distance at which Mercury orbits our sun, Blackman says. Astronomers don’t know how they got there, but our planets aren’t nearly so cozy with our Sun.

[Related: White dwarf star spotted nibbling on the atmosphere of a nearby icy planet]

Another exoplanet orbits a white dwarf and a pulsar, or pulsating neutron star. Cool, but not what’s in our backyard. The last planet orbits so far away from its white dwarf astronomers aren’t even sure if it belongs to that star at all, Blackman says, so none are a good match.

The system Blackman’s team found is a lone star with a gas giant about 40 percent larger than Jupiter that’s traveling in a roughly similar orbit to it. The planet appears to have survived the death of the star “more or less untouched,” Blackman says. The find is the first concrete evidence to the idea that our outer planets could survive the death of the sun.

“We expect that Jupiter and Saturn will survive [the death of the Sun], but we didn’t have direct evidence of this being the case,” Blackman says. If Earth hasn’t yet been destroyed by eight billion years’ time, “it will be full of lava lakes and very inhospitable.”

This glimpse of a white dwarf is a kind of trial run, he says, “this is the first detection of a white dwarf planet using microlensing” but with the Roman Space Telescope, planned for the mid-2020s, scientists hope to find hundreds.

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A team of astronomers found 19 strange radio signals from red dwarf stars, four of which they think could be coming from orbiting exoplanets, potentially marking the first time exoplanets have been discovered using radio frequencies.

Detecting these stars wasn’t a big deal—they were all relatively close to Earth and the team compared the detections with existing optical observations—but “discovering them in radio was a big deal,” because they shouldn’t be bright in radio frequencies, says Joe Callingham, a radio astronomer at Leiden University in the Netherlands and lead author of the study. He and his colleagues used a massive radio telescope called the Low Frequency Array or LOFAR to look at nearby red dwarfs in radio frequencies, and published their findings in the journal Nature Astronomy.

Stars aren’t very bright in radio frequencies. If you could turn your eyes into radio antennae, when you looked into the sky, “you would not see stars, generally,” Callingham says, “you’d see the sun a little bit, you’d see Jupiter really bright, and you would see mostly galaxies.”

The team haven’t proved any of these signals are from exoplanets, but after weighing the possible explanations of the strange radio signals, they consider exoplanets a good bet for four of the stars, Callingham says.

The exoplanet hypothesis is “definitely one possibility,” agrees Jake Turner, a radio astronomer at Cornell University who was not involved in the study, and last year measured a radio signal which may also have been generated by an exoplanet. “There’s so much about [red] dwarfs we don’t understand,” he says, so these readings could also be explained by stellar physics that we don’t yet comprehend.

To make sense of the 19 signals, the team focused on what Callingham calls the most “boring stars.”

Though stars are usually radio-dim, the most active ones—those that have many solar flares and coronal mass ejections—often produce radio signals. There’s also a correlation between how quickly a star rotates and how much activity is in its corona, the shroud of plasma that wreathes the star. The slower and more boring a star is, the less likely it is to give off radio signals, and the more likely the signal is coming from an exoplanet, Callinghan says.

As for how an exoplanet would make a radio signal, we have a great analog for the process in our own solar system.

[Related: Astronomers discover disappearing radio source in the Milky Way’s center]

Jupiter is the loudest pirate radio station in the solar system because it interacts with Io, one of its largest moons, in a way that produces tons of radio waves. By looking at Jupiter, scientists know this type of interaction produces a distinct kind of light called circularly polarized light. The four most promising radio signals had 60-100 percent of their light polarized this way, Callingham says. For comparison, he says, an active star alone shouldn’t be above 50 percent.

It’s hard for a star to produce these kind of radio signals, Callingham says, “that’s how we knew we’re on to something really special.”

Jupiter and Io make their bright radio emission through two means. One is through solar winds. Just like Earth, solar winds blast Jupiter with electrons, and the magnetic field which wraps the planet funnels the electrons to the poles, Callingham says. The shower of electrons makes beautiful auroras and emits radio waves.

Though striking, this is the lesser contributor to Jupiter’s radio emissions. The main method is the motion of Io around the planet, which creates a kind of huge electric generator.

Any electric generator works by making a conductor move within a magnetic field. The magnetic field pushes on electric charges in the conductor and makes them flow. In our solar system, Jupiter is the magnet and Io (along with its cloud of volcanically-launched particles) is the conductor moving around it. This motion accelerates nearby electrons, which then shoot off their excess energy in the form of radio waves which become brighter or dimmer depending on the angle we’re seeing them from.

Astronomers think exoplanets and their host stars could be playing out this Jupiter-Io interaction to generate radio signals which should cycle over time like Jupiter’s.

Callingham and his collaborators are now trying to get more data from the most promising red dwarfs to see if and how their radio signals change over time, which could sort out whether they’re exoplanets.

Astronomers will only be able to verify the existence of these planets with more observations. The upcoming upgrade to the LOFAR telescope, LOFAR2.0, and eventually the Square Kilometer Array project, will allow for much higher resolution data to help solve these kinds of astronomical puzzles, Turner says.

For the time being, Callingham thinks exoplanets aren’t too far-fetched an explanation. “Like our optical colleagues have shown us, most stars do have exoplanets…so it’s actually not that wild,” Callingham says. With thousands of exoplanets discovered in just a few decades, the landscape is changing rapidly. “In 1996 if I tried to do this,” he says, “I would have been laughed out of the room.”

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Plenty of planetary research suggests that Mars was once flowing with water, even if it has none today. But why Mars couldn’t hold on to its lakes and reservoirs, yielding its current dry and rocky terrain, is still an open question—though new research suggests it has to do with size. 

Mars is a pretty small planet. It’s diameter is just over half that of Earth, and it has only about one tenth of our planet’s mass. Because of its compact body, Mars may have never stood a chance at keeping its watery surface. New research shows that Mars’s small size and weak gravity made it easier for water to escape the planet’s thin atmosphere and run away into space. The findings were published in the Proceedings of the National Academy of Sciences.

“Mars’ fate was decided from the beginning,” said Kun Wang, a planetary scientist at Washington University in St. Louis and the senior author of the paper, in a statement. “There is likely a threshold on the size requirements of rocky planets to retain enough water to enable habitability and plate tectonics, with mass exceeding that of Mars.”

The research team examined 20 Mars meteorites and looked at volatile potassium levels. That’s because potassium isotopes can act like a “tracer” to indicate how water likely reacted on the planetary surfaces. The meteorites they examined ranged from 200 million to 4 billion years old. Analyzing meteorites with these different ages allowed them to see how potassium levels, and water levels by proxy, changed over time. They found that when our solar system was forming, Mars lost its elements at a faster rate than Earth, but at a slower rate than our moon. 

[Related: After a few hiccups, NASA’s Perseverance begins its main missions on Mars]

Wang told NPR that the team’s data showed this trend even in the oldest of the meteorites, signaling that Martian water started depleting almost immediately. Some water on Mars did stay long enough to carve out canyons and river beds, he added. But that likely only lasted for as long as it did because of freezing, as the red planet’s atmosphere cooled. 

The new findings could assist future astronomers in their search for life. If planet size can reliably predict the presence of water, then that could help planetary scientists quickly and easily rule out unlikely candidates.

“The size of an exoplanet is one of the parameters that is easiest to determine,” Wang said in a statement. “Based on size and mass, we now know whether an exoplanet is a candidate for life, because a first-order determining factor for volatile retention is size.”

“This does probably indicate a lower limit on size for a planet to be truly habitable,” Bruce Macintosh, deputy director of Stanford University’s Kavli Institute for Particle Physics and Cosmology, told NPR. “Understanding that lower limit is important—there are lines of evidence that small planets are more common than big ones, so if the small ones are dry, then there are fewer potentially habitable worlds out there than we thought.”

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Reddit Solves SpaceX Debris Mystery

Periodic Table of Legos

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JÖRN HELBERT was standing outside a stranger’s apartment in the north end of Berlin with a bouquet of yellow roses. It was June 2020, and the woman behind the door was in mandatory quarantine. She had just moved to Germany from the United States, and as a favor to Helbert, a fellow planetary scientist, she was acting as a courier, bringing rocks far too precious to be put in the care of international postal systems hopelessly backlogged because of the pandemic. Already one shipping snafu had sent the package to a nail salon in Tucson and nearly lost it. Helbert was familiar with the kind of questioning you might run into when carrying geologic samples through German customs, so the flowers were a gift for her trouble.

The handoff had involved so much effort and intrigue that he felt as if the parcel should be in a suitcase that got handcuffed to his wrist. Instead, Helbert was amused to see a rumpled plastic Walgreens bag left outside for contactless pickup. It held 30 disks made of various rocks analogous to those that might be found on Venus. They had been painstakingly collected and analyzed by Darby Dyar, an astronomy professor at Mount Holyoke College in Massachusetts.

Helbert, Dyar, and a team of colleagues were in the last stages of pitching NASA on a mission called VERITAS, which would send a satellite to map Venus at higher resolution than ever before. Despite the pandemic, their deadlines hadn’t budged. NASA selects low-cost (around $500 million) projects through a program called Discovery only every few years. The team was desperate to get the rock disks into Helbert’s lab at the German Aerospace Center, where he was calibrating an instrument for the VERITAS spacecraft that could determine what sorts of rocks make up Venus’ geological formations; getting a better sense of these would help write the planet’s history. Granite could show us where there were oceans. Basalt could lead us to active volcanoes. Stitching the features together could show us the steps that turned the planet into an uninhabitable inferno.

If you imagine that our solar system is a cul-de-sac where Earth is our cozy home and Mars is the empty lot down the street where developers pitch a shiny future, then Venus is the haunted house a few doors down, camouflaged by an overgrown yard and drawn curtains. It’s similar to Earth in size, density, mass, composition, and gravitational pull, but at its surface, it has lead-melting temperatures of more than 850°F and air pressure equivalent to standing under half a mile of ocean water. Its magnetic field is too weak to protect it from the solar wind, it spins backward, and it has a permanent layer of heat-trapping clouds that veil its face from view.

The best topographic radar maps we have were produced in the 1990s, and they’re quite coarse compared to our charts of Earth and Mars. We know Venus’ surface has mountains, valleys, volcanoes, lava fields, and bizarre geological goodies, but among its many mysteries, scientists still don’t even really know what kind of rocks might reside there.

[Related: What NASA’s twin Venus missions hope to uncover]

Venusophiles say it’s embarrassing that we haven’t gotten to know our neighbor better. Magellan, NASA’s last expedition there, left Earth in 1989. Since then, the space agency has launched 14 missions to Mars while researchers submitted about 30 Venus proposals to no avail. VERITAS was already in that ignominious club of the unchosen; earlier iterations had been put forward for more than a decade. During the last round, in 2017, VERITAS and DAVINCI, a very different Venus project aimed at sampling the planet’s noxious atmosphere, had been part of a five-team Discovery shortlist, but hadn’t made the final cut.

After that disappointment, David Grinspoon, one of the DAVINCI scientists, wrote an essay titled “Not Venus Again,” lamenting that he and his colleagues were like long-suffering Cubs fans but if the Cubs had made it to the World Series and lost.

In the spring of 2021, both teams were back at the plate, anxiously awaiting NASA headquarters to call with their Discovery decisions. “I’ve really put my heart and soul into this particular mission, so for me, it is now or never,” says VERITAS principal investigator Sue Smrekar, a geophysicist at NASA’s Jet Propulsion Laboratory in California. “I can’t imagine investing this intense effort again into getting a mission selected.”

Other countries are planning Venus missions, because there are good reasons to go. As scientists have studied solar systems beyond our own with instruments like the recently retired Kepler Space Telescope, they’ve found dozens of exoplanets with Earth-like properties. That prospect has reawakened the question that has confounded astronomers and philosophers alike for millennia. Are we alone? Except here’s the thing: We have a rocky twin world next door that looks nothing like ours. “I want to understand why Earth is the place where life can exist, and that’s what Venus can tell us,” says Martha Gilmore, a planetary geologist who is on both teams. “I think it’s of the highest priority for understanding how we got to be here.”

VENUS SOMETIMES appears as a twilight star that chases down the sun, other times as a morning star that rises at dawn. Early revelations about the planet gave just enough license for wild speculation about what—and who—might be living there. In 1761, Russian physicist Mikhail Lomonosov observed Venus transiting in front of the sun like a roving freckle, a rare phenomenon that allowed astronomers to estimate its diameter. Lomonosov noticed a strange fuzziness around its edges. That haze, he concluded, was a thick atmosphere. Because clouds on Earth were made of water, it stood to reason that Venus should be a very steamy and swampy place.

In the late 18th century, astronomers also developed a theory that the orbs in our solar system got progressively older the farther from the sun they were. By the late 19th, some imagined Mars, the fourth planet, to be covered in ruins of abandoned canals dug by long-dead thirsty beings. Meanwhile, Venus, the second, enjoyed a reputation as our more primordial twin, full of landscapes that resembled our world in the Carboniferous Period 350 million years ago, when fern forests grew, freakish sharks dominated the seas, and four-limbed creatures were just beginning to stretch out across the land. Perhaps old myths that associated Venus with fertility goddesses contributed to this Edenic image. The Victorian poet Alfred, Lord Tennyson gave it “never fading flowers.” Ray Bradbury, in one short story, pictured the planet more grimly as covered in a sickly white jungle with “cheese­colored leaves,” soil like “wet Camembert” and ceaseless rainfall that feels like a thousand hands touching you when you don’t want to be touched.

Lush visions of Venus dried up as new evidence trickled in. One especially damning sign came in 1956, when a team at the Naval Research Laboratory in Washington, D.C., pointed the 50-foot dish of its radio telescope at the planet. They found it emitted the amount of radiation they would expect from an object hotter than 600°F. NASA’s Mariner 2 spacecraft—the first-ever successful planetary probe to leave Earth—confirmed the hot atmosphere during a flyby in 1962.

It was during this decade that astronomer Carl Sagan made a name for himself proposing that a greenhouse effect was at work on Venus, with poison gases in the clouds locking heat in. In October 1967, the Soviets sent their Venera 4 probe there, this being the first time a spacecraft entered another planet’s atmosphere. It beamed back disconcerting data: The air was much denser than expected and was made up of 95 percent carbon dioxide with negligible amounts of oxygen and water vapor. So crushing was this result that in 1968, science fiction authors Brian Aldiss and Harry Harrison put together a mournful anthology called Farewell, Fantastic Venus,gathering suddenly unscientific essays and stories from researchers and sci-fi writers that had been set on the “no-longer magical” world.

Although astronauts lost any hope of planting their boots on Venus, exploration continued. In 1975, Venera 9’s descent vehicle delivered the first photograph of the surface, a 180-degree panorama showing a desolate field strewn with shattered rocks and boulders. NASA’s 1978 Pioneer Venus mission produced the first crude radar maps. But in the decade that followed, NASA launched no planetary science missions. President Ronald Reagan, who took office in 1981, helmed this dark age, focusing the agency’s efforts on near-Earth orbits reachable by the space shuttle.

One casualty was the planned Venus-mapping VOIR (Venus Orbiting Imaging Radar) spacecraft. When the news came in 1982, Dyar, now deputy principal investigator of VERITAS, was a graduate student in plan­etary science at MIT. She arrived that day to find classmates openly crying. Eventually the research community was able to patch together a simpler, cheaper version, which launched in 1989 as Magellan, an orbiting spacecraft that mapped what was beneath Venus’ impenetrable cloud layer by bouncing radar waves off the planet’s surface.

In the early 1990s, then–NASA administrator Dan Goldin established the Discovery program to fulfill his “faster, cheaper, and better” mandate, emphasizing the use of ready-made commercial hardware and software to get small missions off the ground. The second project to launch, in 1996, was Pathfinder, which included a Mars lander and the first-ever rover, a wagon­size vehicle named Sojourner. It was a huge success and drummed up public support for exploration of the red planet. NASA approved projects with increasingly big budgets: the Mars Odyssey orbiter (2001), the rovers Spirit and Opportunity (2003), the still-operating Mars Reconnaissance Orbiter (2005). Those undertakings paved the way for Curiosity, InSight, and now Perseverance. Since the 1990s, the guiding principle for these efforts has been to “follow the water,” looking for conditions that could once have supported life—but undoubtedly driven by the tantalizing prospect of future human exploration.

With so much money going into Mars, that’s where planetary scientists go. Curiosity alone has had nearly 500 working on its 10 instruments, and untold numbers of grad students have cut their teeth on its data. Success begets success in the eyes of the public too. New Mars rovers aren’t presented like $2.5 billion pieces of hardware but lovable extraterrestrial road-trippers who narrate their journeys on social media and share photos along the way. NASA knows how to sell Mars to taxpayers. It’s less clear how to market Venus, hostile to human eyes and rovers alike.

THROUGHOUT THE PAST couple of decades, interest in places beyond Mars hasn’t entirely disappeared. NASA’s next flagship mission, the $4.25 billion Europa Clipper, will launch in 2024 to spend about six years traveling to Jupiter to study the ice shell and ocean of the planet’s sixth-farthest moon. But Venus has been a glaring blind spot, especially considering it’s so close to Earth. (A spacecraft takes only about four months to get there.) Although NASA hasn’t dedicated a line of funding to studying Venus since the 1990s, a passionate research effort has persisted. Scientists are still reanalyzing data from Magellan and even the Pioneer and Venera missions. They’re also looking at info from the European Space Agency’s Venus Express and the Japanese Akatsuki climate orbiter—the only two such undertakings since Magellan.

Sue Smrekar, the VERITAS leader, was a postdoc at MIT when Magellan sent the first results of its radar mapping to JPL. The whole team was assembled, along with many guest investigators from around the world, to look at what she recalls as the “familiar yet alien images.” She thought it was the closest she would come to “setting foot on another world.” Here were topographic surveys of geologic features found nowhere else, such as tesserae, strange upland regions with such chaotic-looking ripples that researchers named them with the Greek word for mosaic tiles. Some scientists think the formations could be the equivalent of Earth’s continents; others believe they might be more like the scum on top of a pond of hardened magma.

Magellan also documented a small number of meteorite craters, most of which were quite pristine, suggesting that Venus’ current surface is relatively fresh, around 500 million years old. Many think this overhaul happened in a planetwide volcanic event, perhaps on par with the end-Permian extinction that wiped out most species on our Pale Blue Dot. Volcanism on Earth is linked to plate tectonics; however, scientists have yet to find evidence of Venus’ crust shifting, so what drives its eruptive properties remains opaque.

The data left gaps Venusophiles were determined to fill in. Magellan’s image resolution was around 100–250 meters across each pixel. VERITAS (short for Venus Emissivity, Radio Science, InSAR, Topography & Spectroscopy) would improve that by an order of magnitude. Perhaps more impressively, it would boost the topographic resolution by two orders of magnitude. In its pitch to NASA, the VERITAS team showed how Hawaii’s Big Island would look in Magellan’s view: like an unintelligible collection of pixels. The VERITAS view brought the volcanic island’s ridges and valleys and the peak of Mauna Kea into sharp relief.

“I often compare where we are with Venus to where we were with Mars in the ’80s,” says Paul Byrne, a planetary geologist at North Carolina State University in Raleigh who’s due to take up a new post soon at Washington University. He’s not part of either mission but has advocated for more research on the planet in general. He leads the Venus panel of the Planetary Science Decadal Survey, which helps set the field’s priorities for the next 10 years. “We had global image coverage of Mars, but it was relatively coarse. And it was when we started to fly more capable instruments there we started seeing stuff that we could never have dreamed we’d see in terms of the detail. We don’t have that for Venus yet.”

[Related: What does the surface of Venus look like?]

VERITAS, which would launch around 2028, would also glean new data about the composition of Venus’ geologic formations using spectroscopy, an imaging technique to identify matter based on how it absorbs and reflects light. Because Venus’ thick clouds block most light, Dyar, Helbert, and their colleagues had to invent a whole new way to interpret the data that can squeeze through the narrow wavelength range that can penetrate the cover.

Helbert created a Venus-simulating chamber in his lab that would heat Dyar’s rocks to ungodly temperatures to test a prototype of the Venus Emissivity Mapper, or VEM, one of the instruments proposed for VERITAS. COVID-19, of course, was the wrench in their international collaboration, especially considering the teams found out only in February 2020 that they were moving to the next level of Discovery program selections. They needed more data from various igneous rocks to expand their calibration of the instrument. During those early confusing months of the pandemic, Dyar sent frantic emails to colleagues across the country asking for samples and soon had a large collection from locations like Pikes Peak in Colorado, Mount St. Helens in Washington, and the Leucite Hills in Wyoming. Some of the samples were the size of softballs and needed to be cut into small disks to fit in the Venus chamber. With her college closed, Dyar appealed to a retired mineral collector who had special saws and grinders in his basement to do the job. In a rendezvous in a Friendly’s parking lot, she received the 30 rock disks that would eventually make their way to Berlin. 

WHILE VERITAS would have its eyes on the ground, DAVINCI+—for Deep Atmosphere of Venus Investigations of Noble Gases, Chemistry and Imaging (the plus sign added for this round of proposals)—is primarily designed to search for clues about the planet’s history in its opaque atmosphere. The concept was born out of a Venus summit in late 2007 and early 2008, but the current principal investigator, Jim Garvin, chief scientist at NASA’s Goddard Space Flight Center in Maryland, has been dreaming of a new expedition since he finished his Ph.D. in the 1980s. The spacecraft would launch around 2029 and drop a parachute-equipped, aeroshell-protected spherical probe that would sail through the cloud cover. Using spectrometers similar to the ones developed for the chemistry lab aboard Curiosity, it would measure inert gases like krypton and xenon (think of them like fossils of the early processes that formed Venus’ atmosphere) as well as hydrogen isotopes, which could determine when and at what rates the planet lost the oceans it is suspected to have had in its early history.

That water-loss data would be hugely important. Michael Way, a physical scientist at NASA’s Goddard Institute for Space Studies in New York, and his colleagues produced models in 2016 suggesting Venus not only had water before Earth did but also was covered in a shallow ocean for some 3 billion years. Those findings have energized researchers and revived the image of a wet world, at least in its past. “You put that 3 billion years of water on Venus next to the 300 million years that Mars had water and you realize that if we’ve been looking for signs of life somewhere else in our own solar system, maybe we’ve been barking up the wrong tree,” says Dyar. 

The DAVINCI+ team also proposes to put a camera on its descent vehicle to capture views of the surface far better than the Venera 9 images that hooked Garvin when he was a student. He’s convinced his spherical probe can see mountains at scales not possible from orbit. To prove it, he hired a UH-1 (Huey) helicopter test crew in August 2016 to take him for a series of daredevil rides over a quarry in Maryland. As the aircraft plunged toward the ground, trying to mimic the path of the descent vehicle, he hung out the window taking pictures of the rocks below. This past winter the team heated a full-scale prototype in the lab to make sure it could operate in the atmosphere long enough to send readings home.

Coloring in our image of Venus’ long-gone seas could help answer the Big Question. In the 260 years since Lomonosov watched the planet’s transit, scientists have developed telescopes so sophisticated they can observe the transit of faint planets in systems thousands of light-years away. Based on their size, their motion, and the wavelengths of light they emit, astronomers can estimate the conditions of the orbs. Some 60 are considered potentially habitable, meaning they appear to have the right parameters to sustain liquid oceans. But by those same parameters, if we were observing our own solar system from afar, we might think Venus should be Earth-like too. “If you can’t understand Venus, which is our closest Earth-like neighbor, what chance do you have of believing anything some astrophysicist tells us about exoplanets?” says planetary scientist Sanjay Limaye of the University of Wisconsin–Madison.

Limaye is part of a contingent of Venus researchers interested in finding out whether its cloud layer could still host microbial life. In 2020, investigators reported in the journal Nature Astronomy seeing signatures of phosphine—a chemical known thus far only to come from biological sources—in the atmosphere. Though claims about the possible discovery didn’t pan out, the news helped to spotlight the planet as an overlooked astrobiology target.

The Indian Space Research Organization plans to fly its own radar-mapping orbiter at the end of 2024—and it’s not the only foreign space agency actively pursuing a Venus trip. The ESA intends to launch a satellite called EnVision in the early 2030s to look at recent geological activity. And Russia is considering a mission called Venera D that would sniff for signals of life. In 2016 NASA launched its HOTTech program to fund research into hardware that could survive at hellish temperatures for at least a couple of months; with such tech, a Venus lander or rover could be a possibility.

What the Venus research community needs most is more data. Lauren Jozwiak, a VERITAS volcanologist at Johns Hopkins University who got her Ph.D. in 2016, says she was told to look elsewhere in her studies since there were few prospects for Venus. An influx of new data, though, will feed the next generation. “There is so much that we don’t know about Venus,” she says.

[Related: What jostling in Venus’ crust could reveal about Earth’s early geology]

In the early hours of June 2, 2021, Smrekar and Dyar were sitting in their respective kitchens on opposite sides of the country, texting back and forth. Neither had slept much. This was the morning they knew they’d find out which Discovery missions NASA had greenlit. Around 5:30 a.m. Pacific Daylight Time, Smrekar got the call: VERITAS had been approved.

“It is an indescribable feeling to work toward something for 10 long years with heart and soul and finally have it come to fruition,” Dyar says. She spent the day wandering around in shock until she could pop corks with her colleagues in a virtual fete. Smrekar was ecstatic. “I don’t plan to stop celebrating for a while,” she says.

When the agency phoned Garvin that same morning, he nearly fell off his chair. DAVINCI+ would be going to space too. The next few days were a blur—his team buzzing. Both missions had beaten out their competitors, spacecraft proposed to explore Jupiter’s moon Io and Neptune’s moon Triton. After a 30-year drought of new NASA missions to Venus, two will rocket there within the decade, the product of countless hours of research and testing, rock fetching, helicopter riding—and relentless optimism.

“We’ve got this brilliant planet sitting next door with a giant atmosphere and a fascinating crust and a history that somehow didn’t end up like our own planet’s,” says Garvin. “To look back in time at what that world was like—probably Earth-like and maybe even better—is an opportunity for the people of planet Earth at this point. Maybe 30 years ago we weren’t ready. But now we are.”

This story originally ran in the Summer 2021 Heat issue of PopSci. Read more PopSci+ stories.

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Astronomers have discovered perhaps the first “super-Earth” with an atmosphere, and say that there’s a strong possibility of the planet having liquid water on its surface. That’s still no Earth — super-Earths are bigger than Earth but smaller than gas giants — but it’s darn close compared to other known exoplanets. Perhaps equally stunning, astronomers simply used a small array of 16-inch telescopes that any amateur stargazer could have in their garage or backyard.

The new world orbits a red dwarf star just 40 light years away from Earth, and became visible to Earth-based telescopes during a planetary eclipse when it passed in front of its relatively dim star. That crucial moment allowed astronomers to not only spot the super-Earth, but also to calculate the planet’s size and mass. They even hope to figure out the chemical makeup of the planetary atmosphere, based on the filtering effect that it has on light from the red dwarf.

Scientists have mostly figured out the existence of super-Earths indirectly, based on the wobble effect that such orbiting planets have on their host stars. The newly-discovered GJ 1214b now joins CoRoT-7-b as the only two super-Earths that have actually been seen passing in front of their host stars. Such instances provide the ideal circumstances for astronomers to gauge characteristics of the planets.

But those passing moments have proved when looking at sun-like stars, where planets have large orbits that make such planetary eclipses relatively rare. Sun-like stars also shine relatively brightly and can blind most telescopes trying to spot any passing planets, which means astronomers would need to rely on serious space hardware such as NASA’s Kepler Space Telescope.

GJ 1214b

In this case, astronomers chose a different strategy of scoping out the more common dim stars. A relative lack of brightness compared to sun-like stars meant that even relatively weak ground-based telescopes could spot any planets passing in front of the stars. The team had barely begun its survey of 2,000 pre-selected red dwarfs when it hit the jackpot, and that bodes well for turning up many more planets.

“Either we got really lucky, or these planets are common,” said David Charbonneau, an astronomer at the Harvard-Smithsonian Center for Astrophysics, during a special media webcast.

Luck also involved finding a super-Earth that orbits its host star once every 38 hours. Such an orbit puts the planet closer to its star than the planet Mercury is to our sun.

GJ 1214b still represents an almost-paradise as far as habitable planets go, because its host star’s feeble light compensates for the close orbit and ensures more balmy temperatures than those of hellish Mercury.

But the crushing atmospheric pressure — not unlike that of Venus — probably means that no life as we know it exists on the planet. That same atmosphere probably also prevents any light from reaching the planetary surface.

Still, Charbonneau thinks that the discovery of GJ 1214b just marks the beginning. He points out that other super-Earths may very well have wider orbits around the same host star, which would mean that they pass less frequently in front of said star. Given some time, astronomers may yet find those unknown cousins to GJ 1214b — and the wider orbits would mean cooler temperatures that could make them more likely candidates for hosting life.

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In our solar system, only one world has just the right size, just the right temperature and just the right home for liquid water. Long ago, at least one other rocky planet had water, too, but it’s gone now; Mars dried up and turned to rust. A distant moon called Europa has a lot of water, but too far from the sun’s warmth, the moon remains frozen. Closer in, Mercury and Venus are too hot to keep it.

“Between the fire and the ice is this green zone, the habitable zone, where a planet could have liquid water on its surface,” said William Borucki, principal investigator on the planet-hunting Kepler Space Telescope. In that zone, conditions are right for thick greenhouse atmospheres, and for planets with sufficient gravity to hold on to them.

Now for the first time, exoplanet hunters think they’ve spotted not one such world, but three, hanging out smack in the middle of that Goldilocks zone, in solar systems very far from this one. The planets are just a tad bigger than Earth and orbit stars very much like our sun. One system, Kepler-62, has two Earth-sized planets orbiting in the cozy habitable zones. The Kepler-69 system has one possibly habitable planet. These could be the most similar worlds to our own astronomers have ever found.

“They are the best candidates so far for habitable planets outside our solar system,” Borucki said.

Here’s the breakdown: The Kepler-62 system has five planets in all: 62b; 62c; 62d; 62e and 62f. The Kepler-69 system has two planets, 69b and 69c. Kepler-62e, 62f and 69c are super-Earth-size planets. 62-e is 60 percent larger than the Earth while Kepler-62f is about 40 percent larger, making both of them “super-Earths.” They are close together, so much that each would appear like our full moon in the other’s sky. Life forms living on either world would not have very far to travel to meet their neighbors.

“Kepler-62e probably has a very cloudy sky and is warm and humid all the way to the polar regions. Kepler-62f would be cooler, but still potentially life-friendly,” Harvard astronomer and co-author Dimitar Sasselov said in a statement.

As for the composition of Kepler-69c, scientists are not sure, but its orbit of 242 days resembles that of Venus. They are too small for their masses to be directly measured, but astronomers think they are likely composed of rock and water without a significant amount of gas surrounding them.

(Possibly) Watery Worlds Of Kepler-62

Just so it’s clear, there are a lot of assumptions in these statements. Astronomers can’t know for sure whether the planets in the Kepler-62 system are rocky, or have atmospheres that could provide sufficient pressure to keep water on their surfaces. They make educated guesses about this based on the planets’ size–too small to be gas giants, so probably rock worlds like Earth–and their location. This gives an assumption about the amount of radiation they receive from their sun, which could warm the worlds enough to keep water liquid and to impact the weather.

“We are not clear what makes up these planets, because we don’t have any [like them] in our solar system. We have to go to models and theory to understand what’s going on,” explained Thomas Barclay, a Kepler scientist at the Bay Area Environmental Research Institute in Sonoma, Calif.

Based on their size and locations, they could have water. If they have water, they could theoretically, maybe, be host to life. We’ll probably never know, because no mission–neither existing nor planned–can detect that. But that doesn’t stop planet-hunters from getting excited, and wondering what waterborne creatures may live there. If there are life forms on any of those worlds, they would impact the planets’ atmospheres in ways that could maybe be detectable far in the future.

Now into its fourth year staring at 170,000 distant suns, the Kepler Space Telescope has racked up plenty of impressive finds, from adorably tiny scorched worlds to gigantic super-Jupiters to binary star systems harboring planets straight out of Star Wars. Today’s news ups the ante, astronomers said.

“Kepler has brought a resurgence of astronomical discoveries, and we are making excellent progress toward determining if planets like ours are the exception,” Borucki said, “or the rule.”

The papers are published in Science and The Astrophysical Journal.

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The dancing lights of the aurora are entrancing, but they’re hardly unique to Earth. All the other planets in our solar system have auroras too, and now, for the first time, scientists have caught a glimpse of an aurora outside our Sun’s neighborhood—and it’s really flippin’ huge.

The aurora of LSR J1835+3259 (which, unfortunately, doesn’t have a catchier name) gives off at least 10,000 to 100,000 times more power than Jupiter’s. If you could stand on the object’s surface without getting crushed by its gravity, “you probably wouldn’t be able to see anything else in the sky because of this intensely dazzling, red aurora,” says Gregg Hallinan, one of the astronomers who discovered the aurora.

LSR J1835+3259 is suspected to be a brown dwarf—an old star that can no longer sustain hydrogen fusion in its core. It’s located about 20 light-years away. It’s about the same sized as Jupiter, but much heavier, weighing in at 50 to 80 Jupiter masses.

“You probably wouldn’t be able to see anything else in the sky because of this intensely dazzling, red aurora.”

About 15 years ago, scientists were surprised to find that brown dwarfs can emit radio waves—usually that sort of activity is left to the more youthful stars. Hallinan’s team found the radio waves were pulsing like the beam from a lighthouse—which they’ve also observed on Jupiter—and they suspected that an aurora might be the cause.

When charged particles from the sun crash into Jupiter’s magnetic field, it creates the solar system’s largest aurora. Jupiter’s magnetic field attracts the charged particles, which collide with molecules in the atmosphere, resulting in tiny explosions of color. And as those charged particles cascade through the magnetosphere, they also emit intense radio waves in pulses.

Closeup Of Jupiter’s Aurora

By watching it for four years, Hallinan’s team found that the brown dwarf’s radio pulses were more similar to Jupiter’s radio wave pulses than to the sun’s, which led the team to conclude that it’s an aurora that’s causing the pulses.

“The signal was consistent with the spectrum that you see when electrons hit the atmosphere, although it was so much brighter than anything we’ve ever seen,” says Hallinan.

The immense power that the aurora emits suggests that the brown dwarf’s magnetosphere is about 200 times the size of Jupiter’s. That’s pretty large, considering Jupiter’s magnetic field is bigger than the sun. You could line up about 430 Jupiters inside the brown dwarf’s magnetosphere.

The team isn’t sure what’s fueling the massive aurora. On most planets, the winds from the sun supply a stream of charged particles–but the brown dwarf doesn’t have a star, because it is one.

The mechanism behind Jupiter’s own gigantic aurora could provide some clues. Jupiter’s aurora is partly powered by the moon Io, which orbits close to the planet, erupting volcanic debris and plasma into Jupiter’s magnetosphere. Perhaps something similar is happening on the brown dwarf, says Hallinan.

“It may be like an Earth-sized planet sitting inside magnetic sphere of this brown dwarf, spewing stuff into its magnetosphere.”

The team suspects that 10 percent or more brown dwarfs may have auroras.

“Maybe having a magnetic field is a really important part of having life evolve on this planet.”

But using radio waves to find auroras is not just about tracking down a pretty phenomenon—it’s also a way to measure a magnetic field really easily, and in the search for Earth-like planets, that could be important.

Earth’s magnetic field protects us from the sun’s harsh radiation as well as damaging cosmic rays. “Maybe having a magnetic field is a really important part of having life evolve on this planet,” says Hallinan. “We want to find out if other planets have these same kinds of shields.”

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At the very center of the image above is the sun-like star HL Tau, surrounded by rings of dust and gas. You may never have heard of HL Tau, but this picture will go down in the astronomic annals as the first high-resolution image of the birth of a planetary system. Using the Atacama Large Millimeter/submillimeter Array (ALMA), an international observatory in northern Chile, scientists were able to capture this image, showcasing the early stages of a planetary system forming around HL Tau—a celestial ultrasound of a distant solar system..

HL Tau, sometimes called HL Tauri, is located 450 light years away in the constellation Taurus. The star has been the subject of numerous studies, and researchers had already discovered at least one embryonic planet in orbit around the star, but they hadn’t actually been able to observe its planetary formation first-hand. They knew that there was a disc of dust and other pre-planetary material surrounding the star, and they even were able to observe the magnetic field of the disc. But with the high-resolution capabilities of ALMA, they were able to get a beautiful image of the birth of planets.

“When we first saw this image we were astounded at the spectacular level of detail. HL Tauri is no more than a million years old, yet already its disc appears to be full of forming planets. This one image alone will revolutionize theories of planet formation,” Catherine Vlahakis, ALMA Deputy Program Scientist and Lead Program Scientist for the ALMA Long Baseline Campaign said in a statement.

In the image above, HL Tau is shining brightly in the very center of the ringed disc. The surrounding bright rings are just dust and gas in orbit around the star, but as they circle HL Tau, the particles of dust smash into each other, sticking together and forming larger and larger bodies. Eventually, these bodies build up into proto-planets, large enough to clear a path through the dust and gas; the trails of these early planets are visible in the image above as dark rings.

“Most of what we know about planet formation today is based on theory. Images with this level of detail have up to now been relegated to computer simulations or artist’s impressions. This high resolution image of HL Tauri demonstrates what ALMA can achieve when it operates in its largest configuration and starts a new era in our exploration of the formation of stars and planets,” Tim de Zeeuw, Director General of the European Southern Observatory said in a statement.

As you can see in the comparison below, HL Tau’s planetary disc (left) stretches for a much greater distance than our own solar system (right). Scientists estimate that even though HL Tau is smaller than our sun, the distance from it to the edge of the pre-planetary disc of dust and gas is three times larger than the distance of our sun to Neptune (2,798,000,000 miles).

Solar system comparison

The image taken by ALMA is particularly exciting for researchers, because it demonstrates the capabilities of the array located in Chile. ALMA captures images in wavelengths that are much longer than the wavelengths of visible light, which in this case allowed them to see the structure of the cloud surrounding HL Tau. If they had tried to look at it using an instrument that collected visible light, the dust and gas would have gotten in the way, yielding an image that was not-so-clear (or as exciting).

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Astronomers may have solved the mystery of why exoplanets of a certain size seem to be so rare. In a new study, scientists have found evidence that certain rare sizes of planets become more common over time, as gas planets shrink down to unveil their rocky cores.

Small planets that orbit close to their sun tend to fit into either larger or smaller size categories, but rarely end up in the middle. This size gap, or “radius valley,” means that after finding thousands of exoplanets, astronomers have turned up with a surprisingly small number of planets between 1.5 and two times Earth’s size—called super Earths and sub Neptunes, respectively. It was only a few years ago that astronomers documented enough exoplanets to notice this lack of certain sizes. We don’t have any in our own solar system, either. Our inner planets, Mercury, Venus, Earth, and Mars, are all below super Earth size.

But it looks like that radius valley fills in with age, says Trevor David, an astronomer at the Flatiron Institute’s Center for Computational Astrophysics who led the study.

David stresses that his team hasn’t proved a cause-effect relationship. They don’t know for certain whether older planets are indeed shrinking down to fill in the gap. But age “appears to be the most likely” culprit for planet size differences, David says. His team explored a few possible reasons why planets could be shrinking as they age.

“It’s yet another proof” that both super Earths and sub Neptunes “seem to be born as one population,” says Hilke Schlichting, a planetary scientist at UCLA who studies planet formation and was not involved in the study. She says the study makes a convincing argument that sub Neptunes lose their atmospheres over billions of years and become super Earths.

[Related: These 6 exoplanets somehow orbit their star in perfect rhythm]

The team assembled a list of more than 700 exoplanets and separated them into two groups: one of older planets and one of more newly formed planets. They found that the lack of middle-sized planets—which was obvious in the younger group—virtually disappeared in the older group.

There are two likely causes for shrinking exoplanet atmospheres. The first is high-energy light—ultraviolet and X-rays—from young stars, which can blast off molecules from a planet’s upper atmosphere. The second is the heat from a planet’s molten core, which raises the temperature of the atmosphere until some of its molecules get enough energy to reach escape velocity and fly free into space, David says.

There’s also a chance asteroid-type impacts are leading to a loss of atmosphere, he says. But that doesn’t really fit the data well.

Much of planet formation is still a mystery. For instance, sometimes a rocky planet can be right next to a gassy planet four times its size, David says. You’d think they would be similar having formed near each other, but that isn’t the case.

Looking at early, still-forming solar systems, called protoplanetary disks, partially explains how some planets end up with huge atmospheres. The gas available in the disk disperses relatively quickly. “It’s a race against time,” David says, for planets to build up enough mass to capture an atmosphere before it disperses. Much of his work is disentangling differences in how exoplanets formed initially and evolved over time.

Schlichting, a theorist, has led the study of the core heating idea in her lab. She says she hopes future research can determine which method of atmosphere loss is stronger or if both are significant contributors. “We are hoping that one is dominant,” she says. Then, “we can figure out which one is dominant in terms of shaping this radius valley.”

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What was Earth’s atmosphere like 4.5 billion years ago? It’s a tough question to answer. Back then, Earth was barely a planet and more like a churning mishmash of rocks. When life eventually took hold, it spewed oxygen everywhere and irrevocably changed the blend of gases we now call air.

But it’s a question that has grown urgent as the study of alien planets outside our solar system—exoplanets—has boomed. Current telescopes can spot atmospheres around worlds bigger and hotter than our own, and the next generation will soon bring the blurry outlines of Earthlike planets into focus. 

To work out what those planets are made of, whether they have water, and perhaps even whether they host life, researchers need to be able to link the gaseous silhouettes with the worlds’ bones: their rocks and minerals.

Earth’s weather, life, and plate tectonics have recycled beyond recognition the materials that first forged our world. But pristine leftovers that escaped the chaotic production of Venus, Mars, and Earth have survived as asteroids. Now, a team of researchers has pulverized, baked, and analyzed a handful of nuggets from those primordial materials to catch a whiff of gases that can’t be collected any other way.

“They’re really the only direct samples that you can hold in your hand and actually study in the labs here on Earth to try to get an understanding of what early Earth or other rocky planet atmospheres might have been made out of,” says Maggie Thompson, an astrophysicist at the University of California at Santa Cruz.

How to make an atmosphere

For gas giants like Jupiter and Saturn, lasting atmospheres come easy. They just grab whatever’s hanging around—usually hydrogen and helium—with their massive gravitational pull.

Rocky, terrestrial planets make their own air. This kind of world takes shape from a swirling cloud of mega-asteroids tens to hundreds of miles across. The coalescing space boulders smash together and heat up to thousands of degrees Fahrenheit. The inferno boils away frozen materials in the rock, and these gases become the planet’s starter atmosphere.

Researchers have long realized that asteroids, as samples of the stuff that Earth formed from, are the key to understanding our planet’s origins. But they’re far away and hard to get to, so instead planetary scientists study the remnants of asteroids that have made their way into the inner solar system and fallen to Earth: meteorites.

[Related: Watch live as the OSIRIS-REx spacecraft snags a chunk of asteroid]

“They really are like leftover Legos of planets in our solar system,” Thompson says. “It’s really lucky that they come to us.”

Meteorite madness

Early attempts to work out the makeup of young Earth’s atmosphere used models. Laura Schaefer, now a planetary scientist at Stanford University, led one such effort in 2010. She already knew what minerals and elements had been found in the main class of meteorites thought to be linked to planet formation. So she used chemistry to predict the gases those materials would release when heated. 

She found that water and carbon dioxide would have dominated the early atmosphere, with traces of less expected gases, including types of sulfur and carbon. It was a reasonable result, but one assuming ideal conditions and pure materials.

Years later, Thompson and her advisor Myriam Telus reached out to Schaefer. They planned to take the Stanford scientist’s simulations and make them a reality, by baking real meteorite fragments in an oven to see what gases would be released. 

Other researchers had heated up meteorites before, but they were typically driven by other questions that required different experimental techniques. No one had ever used the space rocks to cook up a version of Earth’s primordial atmosphere. Schaefer was in. 

“It’s every modeler’s dream that somebody will come along and test their models with real data,” she says.

Baking with meteorites

Telus leveraged her network in the meteorite community to procure a few raisins’ worth of material from three meteorites, one of which had just fallen to Earth in 2019, when it crashed through the roof of a dog house in Costa Rica.

Thompson ground up shavings from the meteorites and stuck them in an oven, where she exposed them to conditions thought to be similar to what the powdered rocks would have experienced 4.5 billion years ago if they had helped form the Earth. She heated them to nearly 2,200 F (1,200 degrees Celsius) in a near vacuum, at pressures a hundred million times lower than at sea level. Then a sensitive instrument meant to search for trace contamination from gases sniffed what came out.

[Related: This distant world is a lot like Earth, but you wouldn’t want to live there]

The proto atmosphere released by the hot meteorite powder was about 66 percent water vapor, 18 percent carbon monoxide, and 15 percent carbon dioxide, along with smaller amounts of hydrogen, hydrogen sulfide, and a handful of other gases. It was mostly in line with what Schaefer had predicted, although with a few differences, such as more sulfuric gases. “That’s something we’re still working out,” says Schaefer, who helped analyze the results. The researchers announced their results last Thursday in Nature Astronomy.

The Santa Cruz group still has roughly 80 percent of their meteorite material left, so they plan to continue their baking. Next, they hope to fine-tune the gas sensor to look for rarer gases (it can only sniff out ten at a time). They’d also like to try switching up their ingredients and cook with a different class of meteorites to see what kind of atmosphere those rocks produce.

From the oven to the stars

The team’s home-baked atmosphere will help astronomers better understand what they’re looking at when the James Webb Space Telescope and the next generation of ground-based telescopes start coming online over the next decade. As the telescopes return raw data describing the light that makes it to Earth from the atmospheres of rocky planets (like those in the TRAPPIST solar system), researchers will compare those observations with atmospheric predictions to see which blends fit best.

Thompson’s atmosphere will be among those. A strong match would tell us how much water and carbon dioxide are in the atmosphere, as well as whether that solar system sculpted its planets from the same type of asteroids ours did.

The research also lays the groundwork for interpreting biosignatures, or signs of life. Organisms on Earth drastically transformed our atmosphere. Now that researchers have a better handle on how the atmospheres of rocky planets might start out, they’ll be more prepared to recognize an atmosphere that life has tampered with.

“To understand biosignatures, we have to get a handle on what’s the natural range [of atmospheres that] rocky planets will make without life,” Schaefer says.

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Two hundred light years away sits a planetary system unlike any other yet discovered. It contains at least six worlds, five of which are locked together in a particular type of gravitational tango. More bizarrely, the planets have arranged themselves with complete disregard for the standard layout that most solar systems tend to follow. The band of misfits, dubbed TOI-178, challenges planetary scientists to refine their theories of how solar systems settle down.

“It’s a milestone system,” says Nathan Hara, an astronomer from the University de Geneva, Switzerland, one of the astronomers who identified the exoplanets. “It’s something that will be studied in the future.”

TOI-178 caught researchers’ attention in 2018, when NASA’s exoplanet hunting TESS satellite spotted a star with a dimming pattern that indicated a first-of-a-kind planetary system. When researchers look for far-off planets, they do so by watching stars and noting when planets pass in front of them, measuring the resulting dim in brightness. Of this system’s three planets, two appeared to share a single ten-day orbit, one chasing the other around their host star.

The configuration was strange enough to merit devoting 11 days of observations on Europe’s CHaracterizing ExOPlanet Satellite (CHEOPS)—the largest chunk of time allotted to a single target for CHEOPS so far—last August.

But when astronomers read through the data, they found that TOI-178 was not what it seemed. Two exoplanets had been masquerading as one, their 15- and 20-day orbits conspiring in just the right way to eclipse the star every ten days, as if they were a single world. “In the TESS data we had an extremely improbable configuration, where one of the true planets was falling exactly between the two transits of other planets,” says Hara. “It had a 1-in-1,000 chance of happening.”

And the longer they watched, the more planets they saw. The CHEOPS observations confirmed intermediate work from other telescopes, and eventually a collaboration of roughly 200 astronomers managed to piece together a more complete picture of the system. The dimming and wobbling of TOI-178′s star betrayed the presence of six exoplanets packed tightly together. The first races frenetically around the star every two days, while the sixth takes three weeks. (Mercury, in contrast, spends nearly three months orbiting the sun.) The team described the system in a preprint on Monday, and it has been accepted for publication in Astronomy and Astrophysics.

One of TOI-178′s most intriguing features is how most the motions of its planets harmonize in a phenomenon known as “resonance.” If you tossed a handful of planets into orbits around a star, you might expect their years to have completely unrelated lengths, but that’s not exactly what happens. Astronomers often observe worlds orbiting such that they find themselves forming the same configuration with their neighbor at regular intervals, similar to how notes line up in music to form chords (mathematically speaking, the ratios of the orbital periods make simple fractions). You can see how the orbits of the TOI-178 exoplanets align—and hear their celestial song—in this video, produced by the European Southern Observatory.

Such a system can form in different ways, but the general idea is that planets in resonance “talk to each other,” Hara explains, almost as if they are “attached by a spring.” When the worlds line up every few orbits, they draw close enough to pull on each other gravitationally, preventing either from drifting out of resonance.

In TOI-178, all planets except the first pair up with their neighbors to form a “chain” of resonances—a structure that actually let the astronomers discover one of the planets when they went to look for a missing link.

The resonant chain also serves as a window into the system’s past. The links between planets are tenuous, and easily broken by common solar system drama such as a near miss with a passing star, or if one planet sends another one flying. The survival of TOI-178′s delicate chain suggests that, as Hara puts it, “nothing too drastic happened in the last billion years.”

Impressive chains of resonance weave together other systems, such as TRAPPIST-1, but what really sets TOI-178 apart is the clash between its orderly orbits and its haphazard arrangement.

Most solar systems put their dense, rocky planets—your Mercuries, your Venuses—up close to their stars. Then the planets get thinner and gassier as you go out (Jupiter is huge, but just a quarter as dense as Earth). Researchers are still working out the details of why this happens, but the general theory is that inner planets tend to run hotter, which boils away their gassy atmospheres, leaving mainly rocky cores behind. Distant planets also benefit from frigid temperatures that let ices play a bigger role in the planet-making process.

When TOI-178 formed, however, it ignored these norms. It starts off reasonably, with two rocky supersized Earths near the star. Then things get wacky. The third planet is nearly the wispiest of the whole system, less dense than Jupiter. The densities jump up for the next to planets, a small hop to a Neptunian density and a big leap up to nearly Martian density. The last planet is the least dense of all.

While the standard ordering is more suggestion than rule, the existence of TOI-178 poses a puzzle to researchers, especially considering that its tidy chain of resonances makes violent, recent reorderings of planets unlikely. “How can you have something which evolved gently like this, but still you have these huge [density] discrepancies,” Hara says. “We are not used to this.”

While theorists mull over how the system came to be, astronomers anticipate expanding their portrait of TOI-178. Future observation campaigns may attempt to extend the resonant chain, searching for additional planets that would add complementary notes to the celestial chords. (The next two links would fall in, or near, the star’s habitable zone).

The host star shines unusually brightly too, which is one of the reasons Hara and his colleagues were able to get such precise measurements of the masses of the planets. It puts out so much light that the upcoming James Webb Space Telescope should be able to deduce the atmospheres of the planets, giving researchers additional clues to how they might have formed.

“It’s the brightest system in resonance,” Hara says, “one which will lead to very rich follow up observations.”

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When Caroline Piaulet first started looking at an exoplanet called WASP-107b, a gas giant orbiting a star in the Virgo constellation about 212 light years away, she was mostly interested in finding out what was inside it. “I essentially wanted to get the most precise data on what the atmosphere was made of,” says Piaulet, a Ph.D student at the Université de Montréal’s Institute for Research on Exoplanets. To do that, she says, she had to first calculate its mass—a routine part of conducting transmission spectroscopy, which astronomers use to analyze the chemical makeup of exoplanets. Instead, what Piaulet found would upend what astronomers know about how some planets form. “We weren’t expecting to find what we found.”

Up until now, planet formation has tended to follow patterns we see in our own solar system. When stars form, they’re surrounded by a disc of dust and gas called a protoplanetary disc; this is the stuff that provides the building materials for what eventually becomes a planet. In classic models, based on what astronomers know about Jupiter and Saturn, gas giants need to have a solid core at least ten times as massive as the Earth to gather enough gas before the disc disappears. Without that giant core, astronomers believed, planets wouldn’t be able to build up and keep the large gas envelopes that make them gas giants.

But WASP-107b is breaking those rules: even though it’s comparable to Jupiter in size, it’s ten times lighter, bringing it closer to the mass of Neptune and making it a “super puff,” or one of the least dense exoplanets ever discovered. Piaulet concluded that the core of WASP-107b is no more than four times the mass of the Earth, which means that more than 85 percent of the planet’s mass can be found in the thick layer of gas swirling around its core. On Neptune, by comparison, the gas layer only accounts for 5 to 15 percent of its total mass.

To make matters even more complicated, WASP-107b is incredibly close to its star—over 16 times closer than the Earth is to the Sun, with an orbital period of just 5.7 days. If the planet had originally formed where it is now, explains Piaulet, there’s no way it would have become a gas giant. “To accrete enough gas to become a gas giant, it has to happen really quickly,” says Piaulet. “So it has to happen in a colder environment, which means it has to be far from the star.” WASP-107b’s existence, then, didn’t make any sense.

To explain how WASP-107b came to be, Piaulet and her team looked towards another planet—and to a theory that previously had only been applied to smaller “super puff” planets. The astronomers noticed that WASP-107c, another planet orbiting WASP-107b’s star but with a much larger orbital period of three years, had an eccentric, or oval-shaped, orbit. “That tells us something about the history of the system,” Piaulet explains. WASP-107b had most likely formed further away from its star than where it is now, and was essentially slingshotted into its current orbit by WASP-107c. While WASP-107b’s orbit normalized into a circle because of its proximity to the star, Piaulet explains WASP-107c’s eccentric orbit “kind of keeps the memory of what happened in the system.”

“This work addresses the very foundations of how giant planets can form and grow,” said Björn Benneke, Piaulet’s supervisor and an astrophysics professor at the Université de Montréal in a press release.

Now that her work establishing the mass of WASP-107b is complete, Piaulet can go back to her original goal of finding out what the planet is actually made of. But, she says, it has forever changed the way she approaches her work. “This is making me think more about the formation of the planets,” she says. “That’s not something I thought about so much before; I was focused more on the chemistry. Now I’m asking what the interior structure can tell us about the history of the planet. Mass and radius tell you much more than you would think.”

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Some 336 light-years from Earth, a giant exoplanet circling a pair of stars may offer clues to a mystery closer to home.

The massive gas world—HD 106906 b—clocks in at 11 times the size of Jupiter, and sits mind-bogglingly far away from its host twin stars at 730 times the distance between the Earth and the sun. According to a paper released last week in the Astrophysical Journal, the distant world could help scientists learn more about whether there is a large Planet Nine lurking in the far edges of our own solar system.

The exoplanet was first discovered in 2013, but it took Hubble’s accurate measurements (and looking back at the planet’s movements over a 14-year period) to pinpoint its bizarre elongated and inclined orbit. HD 106906 b is far from its stars—one orbit, its “year,” is equal to 15,000 years. As the planet advances at a snail-slow pace around its stars, measuring “even a fraction of that orbit requires ultra-precise measurements of its position and motion,” says astronomer Meiji Nguyen, of the University of California-Berkeley, who led the study.

Nguyen says it’s as if Jupiter traveled beyond the Kuiper Belt—a region of mainly icy, dusty debris, around the outskirts of our solar system. If Planet Nine exists, this is how it might orbit the Sun. “The fact that we’ve found a system that behaves like this in nature shows that the Planet Nine scenario is possible and could potentially happen very early on in the evolution of a stellar system,” says Nguyen.

The hunt for the hypothetical Planet Nine has stirred the scientific community. In the past decade, many astronomers have proposed that odd orbital arrangements of objects beyond Neptune mean the existence of a world that has yet to be observed, or possibly some heavy exotic object like a primordial black hole might be lurking out there.

It’s not certain how HD 106906 b achieved such a distant and strangely inclined orbit like we believe our own Planet Nine might have. The prevailing theory, and the one researchers proposed in the new study, is that it formed much closer to its host stars, about three times the distance that Earth is from the Sun. Drag within the system’s gas disk could have pulled it inward toward its stellar duo, Nguyen says. Then, the combined gravity from the whirling twin stars kicked it out onto an eccentric orbit that almost threw it out of the system and into the void of interstellar space, but a passing star may have stabilized the orbit and prevented the world from becoming a rogue planet.

According to researchers, a similar scenario may have played out in the early days of our Solar System to form the mysterious, much sought-after Planet Nine. Its interaction with our giant planets early on in our solar system’s history punted Planet Nine into the boondocks, after which passing stars in our local cluster likely put the brakes.

“The planet’s orbit is very inclined, elongated and external to a dusty debris disc that surrounds its host stars,”  astronomer Avi Loeb, chair of Harvard’s astronomy department who wasn’t involved in the study, told Salon. “In that sense, it resembles the orbit postulated for Planet 9 in the Solar system.”

According to Nguyen, there’s more work to be done on HD 106906 b. Researchers hope to use the James Webb Space Telescope, Hubble’s spiritual successor slated for launch next year, to confirm their data. Additional observations of HD 106906 b could help us determine how to go about hunting for the elusive Planet Nine, too

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Earth regularly endures highly charged belches from our Sun, sometimes even prompting a dancing curtain of ever-changing color known as aurora. But could similar violent eruptions in other solar systems make far-off worlds inhospitable to life?

Earlier this year, astronomers confirmed there were two Earth-like planets orbiting the cool, faint red dwarf Proxima Centauri—the closest star to our sun at 4.2 light-years away. One of them, Proxima Centauri b, is in its star’s habitable zone where temperatures might allow liquid water to exist on its surface.

In a new study, outlined today in The Astrophysical Journal, researchers used a suite of optical telescopes, including NASA’s Transiting Exoplanet Survey Satellite and Australian-based radio telescopes like the Australian Square Kilometre Array Pathfinder (ASKAP) and Zadko Telescope at the University of Western Australia, to observe the stars for 11 nights in a row. Hyper-energetic sun burps are usually harmless here on Earth thanks to our planet’s magnetosphere, but the team was curious what they might look like in other systems. On planets without a magnetic shield, all of that energy could easily wipe out life.

“We thought that Proxima Centauri would be a great sort of laboratory for understanding these phenomena,” says lead author Andrew Zic, who undertook the research while at the University of Sydney. Sure enough, they caught a solar flare and a series of radio bursts. The simultaneous observations allowed the team to link the two events; according to Zic, there is a probability of less than one in 128,000 that they weren’t related.

Red dwarfs are very active stars, crackling with activity and hurling blistering pulses of energy into space. Often, Zic says, solar flares are accompanied by the release of giant bubbles of stellar material known as coronal mass ejections, or CMEs. The findings strongly suggest planets around this type of star—by far the most abundant in the cosmos—are likely to be showered with a lot of punishment over the eons in the form of powerful stellar flares and plasma ejections, dampening hopes that some type of life could exist on its surface.

While Earth gets barraged with intense blasts of solar plasma, our planet’s magnetic field shields us. Whether the exoplanets orbiting our solar system’s nearest neighbor have similar shields remains an open question.

“We think this is a very good indication that we’re seeing for the first time, some solar-like radio burst activity from Proxima Cen that indicates that there may be space weather events occurring around the star,” Zic says.

Still, coronal mass ejections are observationally elusive, and not everyone is convinced that the team truly spotted one. The characteristic burst of radio noise indicated it was a type IV burst,– known for its trailing long-duration. Ofer Cohen, a solar physicist at the University of Massachusetts at Lowell who was not involved in the study, says that “the flare is obviously there, but it is not guaranteed that a CME had been launched from the star.” In his view, a type II radio burst would be a better bet for confirming a CME, since it indicates the shockwave in front of the stellar belch.

“The paper describes an observation and an interpretation. The observation seems ok, but you may argue that the interpretation may go beyond what we can actually tell based on it,” Cohen adds.

Zic agrees that the prospect of finding type II bursts around active stars like Proxima Centauri is a very exciting one. “It would be a really exciting detection because you can actually sort of make out some of the details of the coronal mass ejection.” On the other hand, if a coronal mass ejection is like a bullet leaving a gun, a “type IV burst is a bit like the smoke from the gun.”

Although it’s not direct evidence of a red dwarf CME, it’s the most compelling evidence for a solar-like radio burst from another star to date. And if it’s true, it could mean lower chances of life in our nearest star system. But the picture isn’t totally complete yet. Researchers like Zic are hoping they’ll be able to detect similar events in order to map out the dramatic effects of space weather on solar systems beyond our own.

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Some 322 light-years away in the constellation Libra lies one of the most extreme and hottest worlds discovered by astronomers so far. Launched into Earth orbit last December, the European Space Agency’s shiny new exoplanet-hunting satellite CHaracterising ExOPlanet Satellite (or CHEOPS) spotted exoplanet WASP-189b, a gas giant circling close to one of the hottest known stars with a planetary system.

WASP-189b, the first alien planet studied by CHEOPS, is a strange one: it can reach a toasty 5,792 degrees Fahrenheit, where even iron turns to gas, and it has a year that lasts a scant 2.7 days, orbiting sideways around an egg-shaped star. The details of this bizarre exoplanet were revealed in a study published Monday in the peer-reviewed journal Astronomy and Astrophysics.

“This object is one of the most extreme planets we know so far,” says Monika Lendl, lead author of the study from the University of Geneva. WASP-189b is a hot Jupiter planet, a gas giant similar to our own Solar System’s Jupiter, but with more extreme temperatures.

“We can’t see the planet itself, because it is too close to its bright host star,” Lendl says. But she knows it’s there based on how much the star dims when the behemoth passes in front of it. WASP-189b’s star is larger and a few thousand degrees hotter than our sun, making the star the star appear blue and not yellow-white.

To glean details about the system, Lendl and her team measured that tiny dip in starlight when the planet passes in front of its host star from our perspective. The team also observed the WASP-189 system during occultation—when a planet passes behind a star. “Comparing the system brightness before and during occultation allows us to measure how bright the planet itself is,” Lendl adds. Lendl and her team also saw that the planet’s host star itself was a doozy. It’s not perfectly round, but larger and cooler at its equator than at the poles, making the poles of the star appear brighter. Apparently, the star is spinning so fast it’s being pulled outward at its middle.

The discovery was in 2018 during the UK-led Wide Angle Search for Planets or WASP survey—hence the planet’s name. CHEOPS’ job is not to find exoplanets, but to find out more about exoplanets discovered by other exoplanet-hunting missions like Kepler and TESS with higher quality observations. “This was precisely the mission that CHEOPS had in mind: following up on known discoveries to better characterize those discoveries,” says Jason Steffen, a member of NASA’s Kepler Team who was not involved in the research. “On the whole, it is a great paper that really showcases the capabilities of this satellite.”

To date, researchers have discovered more than 4,000 exoplanets. And on top of that, there are at least as many starlight dips that, under further observation, could turn out to be exoplanets. The hope is that studying extreme systems like WASP-189b will help scientists understand other worlds and provide insights on how unique the Solar System and our Earth are. “We will of course continue exploring a range of planetary systems, and a few more results will soon become public,” Lendl says.

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About 1,300 light-years away, a young triple-star system is warping and splitting a disk of dust and gas where planets could one day form. Unlike the flat disk that gave rise to the planets in our own Solar System, the system’s disk consists of three misaligned rings.

GW Orionis, as the wonky system is known, consists of two stars locked in a close do-si-do that are orbited by a third star farther out at a distance of eight times that of Earth to the sun. According to new research, as the stellar trio move in their complicated paths, their gravities tug on the gas around and between them. The findings, published in Science last week, provide the first concrete evidence that stars’ gravities can carve bizarre and fantastic shapes in planet-forming disks, providing new insight into how planets are born in bizarre orbits.

“This is the first time that we see this disk-tearing effect in a real astrophysical system,” says Stefan Kraus, professor of astrophysics at the University of Exeter and lead author of the paper. “We can directly link it to the gravitational influence from the three stars that are in the center of the disk.”

There are three separate rings with different orientations in the massive protoplanetary disk of the triple system, located roughly 46, 185, and 336 times the Earth-Sun distance from the disk’s center. (For perspective, Neptune is about 30 times the distance from Earth to the sun.) Properly envisioning the shape and cause of the system’s misalignment meant studying GW Ori for a staggering 11 years—one complete orbital period—using different instruments on the Very Large Telescope (VLT) and the Atacama Large Millimeter/submillimeter Array (ALMA). The extensive observations allowed them to reconstruct the three-dimensional structure of the disk torn apart by the influences of the three stars.

GW Ori has long been an exemplar for all the special dynamical effects that go on in such a system. But this is the first time there’s really been a clear picture of the system’s geometry: “This study is really a truly comprehensive look at the stellar orbits and the disk at very high spatial resolution,” says Penn State astronomer Ian Czekala, who was not involved in the study.

An independent team of researchers had also examined GW Ori and its tilted discs in a study published in May. However, the researchers speculate that a separate, existing planet may have caused the disk to be torn apart in the first place—not only by the star trio. “Our simulations show that the gravitational pull from the triple stars alone cannot explain the observed large misalignment,” says Nienke van der Marel, co-author of the May study, in a press release. “We think that the presence of a planet between these rings is needed to explain why the disc was torn apart.”

Kraus and his team don’t rule out a planet as a potential cause: The system’s inner ring has enough dust to build 30 Earths, which he says is sufficient to form a planet within the ring. He adds that a planet formed in this misaligned part of the fractured disk would have a highly unusual orbit.

“What we find here is that multiple stars can move material out of the disk plane and put it onto these extreme oblique orbits,” Kraus says. “That’s a completely new mechanism for forming wide separation planets on misaligned orbits; you can basically get any orbit orientation with this mechanism.”

Future studies will have to determine for certain what is happening in the cattywampus system. With the next generation of telescopes like the European Southern Observatory’s Extremely Large Telescope (ELT) scheduled to come online in 2025, the hunt for young, wonky-ringed stellar systems like GW Ori should pick up steam.

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Space telescopes like Kepler and the Transiting Exoplanet Survey Satellite (TESS) have made hunting for exoplanets an industrial pursuit. Their mechanical eyes watch thousands of stars simultaneously, and software efficiently sifts through the mountains of resulting data, highlighting only the most promising stellar flickers and wobbles for manual confirmation. The process has revolutionized planetary science like the assembly line revolutionized manufacturing: just 28 years after the first confirmed exoplanet discovery, NASA’s catalog is bursting with more than 4,000 confirmed exoplanets spanning more 3,000 systems.

Sandra Jeffers, a researcher at the Institute for Astrophysics at Goettingen University in Germany, is part of a team taking a more bespoke approach, searching nearby stars one by one for high-quality exoplanet targets that could someday be studied directly. Now years of analysis based on decades of data has uncovered one of the most promising targets yet, the group announced Thursday in the journal Science. Two, possibly three “super-Earths” orbit a bright but quiet red dwarf star sitting just 11 light years from Earth. Astronomers generally struggle to infer much more than an exoplanet’s orbit or size, but the rare combination of traits in the so-called Gliese 887 system means that upcoming telescopes may be able to access information about the gases surrounding the planets—and therefore learn something about their climates—as well.

“We know it’s the best star in close proximity to the sun with the aim of understanding the exoplanets atmospheres,” Jeffers says.

Jeffers leads a collaborative project called RedDots, which targets stars within about 16 light years of the sun—most of these are dim, red dwarf stars, hence the name. She’s spent years chasing down astronomers at conferences who she suspects might have recorded observations of nearby stars and inviting them to collaborate. In the case of Gliese 887, Jeffers managed to cobble together a dataset representing 20 years of work from more than two dozen researchers on a handful of telescopes. “[The field of] exoplanets can be cutthroat,” she says, “but working with this team it was very cooperative.”

The group saw hints of planets in 2017, but their observations were too sporadic to be conclusive. In the fall of 2018, they went back and stared at Gliese 887 every night for nearly three months with the High Accuracy Radial Velocity Planet Searcher (HARPS) instrument in Chile.

That did it. By generating a visualization analogous to a time-lapse movie, the team could clearly tell that Gliese 887 was jiggling. Specifically, it bobbed approximately every nine, and every 22 days—unmistakable signs of two nearby planets, which they concluded weigh at least 4 and 7 times as much as the Earth, respectively. Both worlds orbit a bit too close to their sun for water to likely exist on their surfaces, but the team also noticed a tentative sign—a single jiggle—of a potential planet making a 50-day orbit in the star’s temperate zone. They have since returned for a further two months of observations, which should be enough to prove or disprove the third planet with more number crunching in a future paper.

Although the two confirmed planets seem too hot to comfortably host life as we know it, the system is an observational dream. On top of being just 11 light years away (our nearest star system is about three times closer, but many exoplanets are hundreds to thousands of light years away), Gliese 887 is an unusually chill star. It has few sunspots and rarely flares up, unlike many of its hothead red dwarf peers. Its calm disposition makes it an ideal target both practically (a calmer star is more of a blank canvas that cleanly showcases planets’ features without completely washing them out), and scientifically (because it’s less likely to strip its planets of their atmospheres with bombastic solar flares).

Current telescopes can’t quite make out the atmospheres around such planets since they don’t pass directly in front of their stars—a special case that has made it possible for astronomers to peep the atmosphere of certain other exoplanets. But Jeffers expects the next generation of telescopes to change that. “This is an ideal science case for the [James Webb Space Telescope] due to be launched next year,” she says.

Other researchers are cautiously optimistic. “This one’s good,” says Tomas Greene, an astrophysicist at the NASA Ames Research Center who studies how the space-based Hubble successor will help study exoplanet atmospheres. “The first question is whether it has an atmosphere or not, and JWST should be able to help with that.”

Specifically, JWST should be able to watch for fine temperature variations of the whole system as the planets swing in and out, alternatively showing their daytime side and nighttime side to Earth. A naked, rocky planet with no atmosphere should experience wild temperature swings. It’s groundbreaking work, but it won’t be easy. “These will be difficult observations that will take a lot of time,” Greene cautions. Researchers will need to stare at the system for multiple orbits of each planet, much like they did for the HARP observations.

Not even JWST will have keen enough eyesight to spot the individual planets and find out which particular gasses might swaddle these super-Earths. Those studies may have to wait for the next generation of ground based telescopes, such as the Giant Magellan Telescope and the Thirty Meter Telescope, which could come online toward the end of the decade. With better resolution than JWST and (somewhat) less competitive observing time for longer projects, these instruments should be able to accumulate enough direct light from the planets to spot signs of water, oxygen, and perhaps methane, Greene says. While these nearby worlds may not be top candidates for life themselves, they could serve as windows into the nature of other exoplanets too far off to image directly.

Understanding alien atmospheres represents one of the next frontiers for exoplanet science. One can infer only so much about a world from its location and size, but knowing the molecules that surround it takes researchers a step toward being able to predict its climate. Gliese 887′s second planet, for instance, could turn out to be a somewhat hospitable place, Jeffers says, if it has an atmosphere to help spread the heat around. “It could be a hot beach day on the actual surface of the planet,” she says.

While they wait for JWST to launch and for construction on giant ground telescopes to move forward, the RedDots team remains focused on readying as many nearby targets as possible. The team has already detected planets around Proxima Centauri (four light years away) and Barnards Star (six light years away), and they intend to keep systematically working their way out, uncovering our nearest neighbors one by one.

“That’s our long-term goal,” Jeffers says, “to get them all.”

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In 2009, the Kepler space telescope constantly watched over some 200,000 stars in our corner of the Milky Way. It was looking for where life might exist—by pinpointing small, rocky planets in the temperate zones of warm, yellow suns, and figuring out just how special Earth is in the grand scheme of things. While the mission revolutionized the study of exoplanets, those main objectives went largely unfulfilled. A mechanical failure cut short Kepler’s initial survey in 2013. Astronomers would later discover just a single Earthlike planet in its dataset.

A decade later, researchers are finally closing in on some of the answers to the questions Kepler raised. Earthlike planets are probably rare, but not exceedingly so. Roughly one in five yellow stars could have one, according to a new analysis of Kepler’s data published in May in The Astronomical Journal. If the researchers’ conclusions are correct, that would mean the Milky Way might be home to nearly 6 billion Earths. Yet of the 4,000 likely exoplanets we’ve spotted, just one looks anything like our home planet. So where are the rest?

“[Truly Earthlike planets] are not hiding per se, it’s just that the sensitivity of our telescopes is simply not good enough yet [to find them],” says Dirk Schulze-Makuch, an astrobiologist at the Technical University Berlin, Germany, who was not involved with the research.

If astronomers want to find Earth 2.0s, research calculating the frequency of such worlds will give future telescopes their best chances of success.

In the current context of exoplanets, the phrase “Earthlike” doesn’t necessarily imply a pale blue dot. From a telescope’s point of view, there’s no dot at all—just an occasional dimming of a star as a planet passes by, blocking some tiny fraction of its light. Yet from this flickering, researchers manage to extract a few key facts. Deep flickers indicate giant planets, for instance. And frequent dimming is the mark of a planet in a fast, tight orbit. A planet earns the moniker Earthlike if these characteristics place it in the star’s so-called “habitable zone,” a balmy band of orbits where back-of-the-envelope math suggests the star’s warmth will allow surface water to stay liquid.

Michelle Kunimoto, the exoplanet scientist who led the recent analysis, adopted one standard definition of what it takes to be an Earthlike planet: a world between three-quarters and 1.5 times as large across as ours, orbiting a sun-like (“G-type”) star, at between 0.99 and 1.7 times our orbital distance. Only Earth satisfies those criteria in our solar system, with Mars being too small and Venus orbiting too close for inclusion.

Worlds checking all three boxes are almost certainly out there, as Kunimoto’s work, which earned her a PhD from the University of British Columbia, suggests. But they’re hard to spot. Dimming from small planets is hard to see. Plus, they might transit in front of their star just once every few hundred days—and astronomers need at least three transits to confidently claim a detection. To make matters worse, yellow suns are rare to begin with, making up just 7 percent of the 400 billion stars in the Milky way. The vast majority of the galaxy’s stars are dim red dwarfs, which may bathe nearby planets in lethal flares.

Mission planners didn’t know it at launch, but Kepler had almost no chance of completing its initially intended search. To rack up three transits of slower planets orbiting at the outer edge of their suns’ habitable zones, the telescope would have needed to peer unwaveringly at the same patch of sky for more than seven years. But its pointing machinery broke down after four, long enough to find planets only in roughly the inner half of their stars’ temperate zones.

What’s more, Kepler was designed with our sun in mind. But our star turns out to be special in more ways than one. “The sun tends to be quite quiet,” Kunimoto says, while Kepler’s stars crackled more from their intrinsic burning. “Essentially, it’s a lot harder to find the Earthlike planets [than mission designers expected].”

Kepler delivered the scientific goods in the form of a huge haul of thousands of exoplanets, mostly massive giants hugging their host stars. But researchers have been trying to infer the less epic, more familiar worlds that Kepler couldn’t quite make out ever since. (Kepler 452b, which is 10% wider than Earth and has a year that’s only three weeks longer than ours, is one prominent Earthlike exception.)

The new work builds on a method developed by Danley Hsu, an astronomer at Penn State, in 2018. Previously, many researchers assumed there’d be an even spread of planet sizes and orbits, but as the population of exoplanets has grown, some kinds of worlds seem common than others. For planets with years shorter than 100 (Earth) days, for instance, many are 50% wider than Earth and many are 150% wider, but few have twice our planet’s girth. To accommodate these unexplained oddities, Hsu and Kunimoto both broke the Kepler data into many different categories of size and orbit and analyzed them all in a more independent way. Kunimoto went a step further and generated her own list of exoplanet candidates, not relying on the official catalogue.

In the end, Kunimoto found that an Earthlike planet may circle one in approximately every five sun like stars. She stresses that this figure represents an upper limit, however, and that the worlds could well be somewhat rarer. Her results represent an emerging consensus that the Earth-to-sun ratio of the local Milky Way should hover in the ballpark of 1:10. That figure remains a bit rough, Kunimoto acknowledges, but it’s tighter than the wide ranges published previously, which suggested between one earth per fifty suns, to two earths orbiting every single sun.

Schulze-Makuch calls the estimate “reasonable” and says that this kind of research gives us a valuable glimpse at the answers to otherwise unknowable questions, such as “whether our solar system is typical or kind of a freak system.”

He cautions, however, against letting one’s imagination run wild with images of a galaxy awash in billions of blue and green, cloud-studded orbs. The limited criteria of orbit, size, and star type say little about whether the planets have protective atmospheres and magnetic shielding, water, or the materials needed for life to emerge.

Estimates like Kunimoto’s may also shape future missions and give them more of a chance of finding more Earthlike planets than Kepler had. The more common these planets are, the more mission planners will be able to focus on designing instruments that scrutinize individual worlds, as opposed to wider sweeps.

Schulze-Makuch hopes, for instance, that the Keplers of the future will carry “star shades” that block out stars to capture exoplanets as single pixels, whose variations could betray the passage of seasons or the presence of ice caps. Such innovations could narrow researchers’ definitions of what it means to be an Earthlike planet, but he predicts a clear-cut discovery of a true Earth 2.0—one sculpted by life—remains a long way off.

“If we just use the technology we have right now,” he says, “it feels like we’re light years away.”

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With astronomers constantly discovering new exoplanets orbiting distant stars and planetary scientists better understanding the warm, wet corners of our own solar system, the universe is looking more and more hospitable to life. Until someone spots far-off extraterrestrial technology or uncovers a more local microbe, the existence of extraterrestrial life will remain an open question. But that doesn’t stop some from trying to narrow it down.

In the absence of hard proof, two researchers have made a new soft estimate of how alone humanity might be based on the (limited) information at hand. Their calculation, which appeared Monday in the Astrophysical Journal, blends current astronomical observations with one big assumption—that life on Earth is in no way special—to conclude that dozens of radio-capable civilizations may currently exist in the Milky Way, with 36 being the most probable number. They consider that figure to be a low-ball prediction but admit that they’re playing a highly uncertain and theoretical game, one guided by an infamous formula first laid out by astronomer Frank Drake in 1961.

“The Drake Equation is our best and only tool for trying to tackle this age-old question, even though it’s based on things that are still wildly speculative,” says Tom Westby, an engineer at the University of Nottingham in the UK and coauthor of the research.

Westby and his colleague, astrophysicist Christopher Conselice, are far from alone in their fascination with the Drake Equation, which inspires multiple publications each year. Such calculations take something of a gambler’s approach to astrobiology. For example, given what’s known about the abundance of stars and habitable planets, and making some intelligent guesses about the likelihood of life developing on those planets, how many instances of complex life might one bet have emerged?

The challenge, naturally, is that the calculation rests on a string of assumptions, some of which require significantly more guesswork than others.

Westby and Conselice focused the bulk of their analysis on what has been measured with decent accuracy—stars and planets. They considered observations of how quickly other galaxies generate stars, how many of those stars have the rich materials necessary to build planets, and how many planets NASA’s Kepler telescope has spotted in our own galaxy.

For the unknowable parts of the Drake Equation, such as the odds that hospitable planets sprout life, and the chances that life can grow complex enough to develop radios, they turned to philosophy. Leaning on a notion called the mediocrity principle, they assumed that humanity has nothing special going for it. If a sufficiently Earthlike planet exists, they presume, technologically capable life will inevitably evolve there after about five billion years, just as it did here. For the same reason, the duo also assumed that a civilization survives for at least 100 years after switching on their radios, just as humanity has (so far).

These are huge assumptions, Westby agrees, but he suggests that they’re a necessary and reasonable evil for doing such a calculation. “That’s the great problem with astrobiology, trying to extrapolate from one data point here on Earth, he says. “But if we are one of a sample, we should expect ourselves to be typical in most respects.”

Other researchers, however, have criticized this premise. David Kipping, an astronomer at Columbia University who recently published an analysis of the odds of extraterrestrial life based on a different statistical framework, pointed out that we have no way of knowing whether humanity is the exception or the rule.

“If you take a lottery winner and ask them how many tickets they had to buy to win, they’d probably say a few dozen or so, but that doesn’t mean that we should expect everyone wins the lottery after just a few tries,” he explains in an email to PopSci. “Winner’s bias distorts their view of reality. This is the fundamental flaw in their argument.”

And there are reasons to think Earth might be a special place. Our yellow sun, for instance, is not so mediocre in a galaxy where red dwarf stars are the norm.

But if we didn’t hit any particular cosmic jackpot, we should expect company in our mediocrity. After mixing together their observations, estimates and guesses, Westby and Conselice calculated that between four and about 200 civilizations (and most likely about 36) could be alive and broadcasting at this very moment. As he crunched the numbers, Westby felt encouraged by this Goldilocks result—not so large that astronomers should be deafened by alien radio stations but not so tiny that no intelligent life should exist anywhere. We know that we’re here, at the very least.

“One of the most satisfying moments when I was throwing all the numbers together into the final simulation, that [final] number [of 36 civilizations] was relatively close to one,” he says, in comparison with less plausible estimates like a billion or 0.00000001. He adds that he considers the figure “a bare minimum based on our toughest assumptions,” such as “assuming we are near our own extinction.”

The pair also ran the numbers for relaxed assumptions, such as technological civilizations developing faster than the 5 billion years it took for us to emerge here on Earth, and the possibility that such species can survive for extended periods of time, keeping their radios on for longer than a century. In those cases, they found that thousands of civilizations could be broadcasting at this very moment, rather than dozens.

The results give searches for extraterrestrial transmissions long, although not quite impossible odds. Enthusiasts hoping to establish contact, however, may not want to hold their breath. Even under the researchers’ more optimistic assumptions (which yield nearly 3,000 currently broadcasting civilizations), our nearest neighbor would likely live almost 2,000 light years away, making an inter-civilization text message a four-millennia affair.

But the Milky Way may not have always been such a sparse and lonely place. Westby notes that the galaxy peaked (with regard to star production) about 10 billion years ago. Perhaps five billion years after that, when microbes were just getting started on Earth, would have been the prime time for radio-based socializing.

“We might be quite late to the party,” Westby says.

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520 light-years away from Earth, a baby planet is born. While thousands of exoplanets have been identified so far, researchers at the European Southern Observatory’s Very Large Telescope, or VLT, in Chile, have captured the birth of a planet for the very first time. Nestled in a thick disc of dust and gas surrounding a young star named AB Aurigae, a fiery spiral twists around the planet’s site of birth.

The rose-like spirals, which often herald the birth of baby planets, signify how the young objects disrupt the gas, causing waves as if it were a boat on a lake. The dandelion yellow twist region near the spiral’s center lies at the same distance from the star as Neptune from the Sun, or around 2.8 billion miles. Altogether, the twist, described as a spiral arm in a study published Wednesday in the journal Astronomy & Astrophysics detailing the image and its discovery, is caused directly by the formation of this young planet.

“The twist is expected from some theoretical models of planet formation,” study co-author Anne Dutrey of the Astrophysics Laboratory of Bordeaux (LAB) in France explained in an ESO press release. “It corresponds to the connection of two spirals—one winding inwards of the planet’s orbit, the other expanding outwards—which join at the planet location.” The spirals allow gas and dust to accumulate on the growing planet.

Planets form from grains of dust smaller than the width of a human hair, emerging from expansive, donut-shaped disks of gas and dust that float around young stars, according to NASA. Gravity and other forces smash and fuse the materials within the dust, and they accumulate and grow like snowballs. Over millions of years, these snowballs transform into hard pebbles, then mile-wide rocks. Billions of years later, you’ll have an infant planet on your hands.

This mesmerizing image is the deepest photograph ever taken of the AB Aurigae, or The Charioteer constellation. Observations of this constellation were first made a few years ago with the Atacama Large Millimeter/submillimeter Array (ALMA), but only this year did Anthony Boccaletti and a team of astronomers from France, Taiwan, the United States, and Belgium collaborate to capture the clearest image of the area to date by turning the VLT in Chile toward the young star.

European Southern Observatory is in the midst of constructing the Extremely Large Telescope with a 39-meter-wide main mirror, the largest of its kind, which will provide an increasingly intimate glimpse into deep space. With the goal of becoming operational in 2025, the new instrument could discern small dust grains and other materials from planet-bearing discs like this one, which will be crucial in a more nuanced understanding how planets are born. “We should be able to see directly and more precisely how the dynamics of the gas contributes to the formation of planets,” Boccaletti said in the release.

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After centuries of watching the skies, the map of our local solar system has grown quite detailed. We live on one of the rocky inner planets. Next there’s a belt of asteroids, two gas giants, two ice giants, and then a second belt of many smaller icy bodies. In the impenetrable outer solar system, however, lies an unseen dragon, researchers have come to suspect.

Scanning the darkness, astronomers have managed to catch a few glimmers of what might fill the nether regions far beyond Neptune. And what they see doesn’t make sense. Where researchers predicted chaos—strewn flotsam leftover from the solar system’s tumultuous formation—they see unexpected order. Orbits of distant objects cluster together. Their points of closest approach stop short of a certain line for no apparent reason. In a handful of such patterns, many scientists see the work of some invisible entity.

“There has to be a lot more mass out there,” says Ann-Marie Madigan, an astrophysicist at the University of Colorado Boulder.

The leading theory is that a giant planet perhaps ten times heavier than Earth—Planet Nine— pushed its smaller neighbors around. A painstaking search for the dim bully has been underway for a few years, and as it stretches on alternative ideas are bubbling up. Madigan and collaborators, for instance, have found that a vast disk of smaller bodies could have identical effects, Scientific American reported last week. Other researchers have gone to the other end of the size spectrum, suggesting that the mystery object could be a softball-sized black hole. If either team is right, and there is no large object to find, current telescope hunts could continue to come up short. In that case, astronomers would have to get more patient, and potentially more creative.

One challenge to the Planet Nine theory is that while it explains the odd orbits of objects astronomers see today, theorists aren’t sure how such a huge planet could exist in the outer solar system. The sun’s gravity weakens along with its light, so a large planet that formed out there should have gotten snatched away by a passing star. Or if it started out close to the sun and then drifted outward, what stopped it? “If it’s a planet, it’s a weird place for a planet to be,” says James Unwin, a physicist at the University of Illinois Chicago.

But Madigan’s simulations have convinced her that she can get the weird, clustered orbits without the headache of Planet Nine. As the solar system formed, she says, Jupiter and Saturn should have punted lots of planetary rubble into long, oval orbits that collectively form an undetected washer-shaped disk beyond the realm of Pluto. Other researchers have assumed the tiny masses of any objects out there should amount to rounding errors math- and modeling-wise, but Madigan has discovered that they might add up after all.

When she runs digital models of the solar system, she finds that at one point in the distant past, the disk could have morphed into a short-lived cone before relaxing back down into a “puffier” disk. And when the dust settles in such systems, they display the same aberrations that inspired the Planet Nine hypothesis, according to two not-yet-peer reviewed publications posted this spring. “You can explain everything that’s been anomalous in the outer solar system,” Madigan says. “And that’s not something I say lightly.”

Still, she points out that her story requires its own leap of faith. For the disk to completely supplant Planet Nine, it needs 20 Earth masses of material, the absolute maximum amount of leftover debris predicted to exist. “We’re really just at the edge of what is reasonable,” she says.

Another team has proposed a smaller disk that operates through a different mechanism. This object could shoulder outer solar system sculpting responsibilities with Planet Nine, says co-author Antranik Sefilian, a doctoral candidate at Cambridge University, letting the theoretical size of both structures shrink.

Whether the culprit is a perfectly placed planet, an especially massive disk, or some combination of the two, astrophysicists are leaning toward the conclusion that something improbable has taken place in the outer solar system. And some are leaning farther than others.

Last fall, Unwin co-authored a publication speculating that the mystery mass could be a petite black hole left over from the formation of the universe. No such “primordial” black hole has ever been detected, but one survey has found circumstantial evidence that either rogue planets or black holes of Planet Nine-like mass might roam the Milky Way. If our sun could capture the former, Unwin reasons, why the latter? “This is a crazy idea,” he says, “but it’s not an unreasonable one.”

The tough task of deciding amongst the not-unreasonable ideas will likely fall to astronomers. Mike Brown, an influential champion of the Planet Nine theory, is leading a search for the elusive body that could end the debate at any time. Just last week while combing through astronomical data he spotted a point that looked promising, he recently recounted on Twitter, although it turned out to be a mock object he had injected to make sure his search process is working.

If Brown sees nothing, the next-generation Vera C. Rubin Observatory, which is anticipated to take its first images this year, will likely deliver a decisive ruling within five years. Because it will spot far fainter objects than current telescopes can, Madigan expects it to either pinpoint Planet Nine or to start mapping out the objects in her disk’s inner edge. Or, it could spot enough new objects that today’s observed patterns melt back into disorder and there ends up being no mystery to explain.

In the unlikely event that all current telescope surveys fail, and the anomalies endure years of the Vera C. Rubin Observatory’s operations, Unwin’s primordial black hole theory might start to look even more reasonable. Edward Witten, a theoretical physicist and string theory pioneer, imagined such a future last week when he published a pre-print describing extreme measures for locating the absolutely invisible: send out a search party.

Inspired by Breakthrough Starshot, an ambitious project that aims to someday send nanoprobes to the nearest star, Witten did the math on spraying a fleet of simple probes out in many directions, in the hopes that one might quiver as it flew past the black hole. Equipped with light sails, the probes would fly at perhaps one percent of the speed of light (pushed by a powerful Earth-based laser beam), bringing the journey to the realm of the theoretical black hole down to about a decade. Such probes could, if sensitive enough, complete a definitive map of mass in the outer solar system, be it in planets, disks, black holes, or all of the above.

A response published this week pointed out that once the probes leave the lee of the solar wind, jostling from charged particles might mask the tug of any black hole. Even those used to thinking big, however, acknowledge that the scheme will have to overcome a few more pressing hurdles first. Developing the launch infrastructure is expected to cost at least half a billion dollars, and the necessary laser and materials technologies don’t exist today.

“This is a super fun idea,” Unwin says. “However, it comes at a premium price tag.”

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Far beyond our solar system, rocky planets with atmospheres dominated by hydrogen gas could potentially support life, indicates a paper published this week in Nature Astronomy. In an experiment involving sealed bottles and some very hardy microbes, scientists at MIT discovered that both yeast and E. coli can grow in an environment with an atmosphere composed purely of hydrogen—that’s a far cry from Earth’s nitrogen and oxygen-rich air that humans and many other lifeforms thrive in. This means that life might be found in a broader array of alien habitats than we’ve previously recognized.

When scientists envision habitable alien worlds, they imagine these places as having Earth-like atmospheres dominated by nitrogen or carbon dioxide like those found on Mars and Venus. Recently, though, researchers have begun to suspect that planets with other types of environments might also be able to support life. In particular, some scientists have zeroed in on hydrogen-rich atmospheres.

“Hydrogen-rich environments on Earth are incredibly rare and not well known,” Sara Seager, an astrophysicist and coauthor of the new research, told Popular Science in an email. To date, astronomers have yet to identify any terrestrial planets elsewhere in the universe with hydrogen-rich atmospheres, probably because the atmospheres surrounding rocky planets are generally more difficult to detect than those of gas giants. But it’s likely that these rocky, non-gaseous planets with hydrogen-rich atmospheres are out there, and more sophisticated telescopes are being developed that might begin spotting them in the next few years.

“Today we use Hubble and ground-based telescopes,” Seager said. But in the future, she said, scientists will rely on more powerful tools such as the James Webb Space Telescope, which is scheduled to be launched into orbit in 2021.

With this new technology, planets with hydrogen floating above their surfaces will actually be easier to find than their more Earth-like cousins—because hydrogen gas is so light, their atmospheres should expand much farther into space.

Suspecting that worlds with hydrogen-rich atmospheres were out there waiting to be discovered, Seager and her team wanted to show that life could thrive in these areas. “We decided to do a simple experiment to communicate clearly to astronomers that life can survive and thrive in hydrogen environments,” she said.

While hydrogen by itself isn’t harmful to life, nobody had ever grown microorganisms in a 100 percent hydrogen atmosphere before. For their experiment, Seager and her team decided to put yeast and E. coli—two organisms that can survive without oxygen but don’t at first glance seem well adapted for hydrogen-rich habitats—to the test.

The researchers grew colonies of yeast and E. coli inside bottles sealed off from the surrounding air. In addition to a nutritious broth for the microbes to feast on, the bottles contained a range of different atmospheres, including pure hydrogen, regular air, and other blends of gases likely to exist on other exoplanets.

Both the yeast and E. coli were able to survive and reproduce in the 100 percent hydrogen atmospheres, although more slowly than in air. The conditions Seager and her colleagues created in the lab don’t perfectly mimic what scientists would expect to find on an actual planet—its atmosphere would include some amount of other gases besides hydrogen, and it might have much stronger gravity or otherwise differ from Earth. However, the fact that simple bacteria as well as relatively complex microbes like yeast could eke out a living in these conditions improves the likelihood that planets cloaked in hydrogen could be inhabited by some form of life.

Now that researchers suspect that hydrogen-rich rocky worlds are out there, and that microorganisms can thrive on them, the next step is to figure out a way to identify alien life from far-away Earth. One way is to search for evidence of so-called biosignature gases. On Earth, lifeforms, like plants and photosynthetic bacteria, can produce these specific gases. Theoretically, identifying them on another planet would be a good indication that life exists there.

During Seager and her colleagues’ experiment, the growing E. coli discharged dozens of different gases, including some like ammonia that scientists would consider promising signs of life if their instruments spied them on a distant planet. This means future telescopes could perhaps detect the kind of life dwelling in a hydrogen-filled atmosphere. Now we just need to find these strange worlds.

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On April 24, 1990, the Space Shuttle Discovery blasted off from Florida with an instrument that would forever divide astronomy into two eras: the time before space telescopes, and the time after.

From its perch above Earth’s fuzzy atmosphere, the Hubble Space Telescope has spent three decades peering into the darkness, indiscriminately collecting whatever stray light beams found their way to its giant mirror. From local moons, to distant planets, exploding stars, and far off galaxies, the world’s first and best-known space telescope has snapped images of them all, producing a voluminous gallery topping 1.4 million observations. Now NASA is celebrating the 30th anniversary of Hubble’s launch with one more picture—and it’s a doozy.

Taken earlier this year specifically to commemorate the observatory’s milestone, the image captures stars being constructed from gas swirling in the Large Magellanic Cloud, a small galaxy circling our own that can be seen in the skies of the southern hemisphere. The blazing young stars in the center each outweigh our sun by a factor of ten, and the blue cloud (colors indicate different gas types) represents detritus expelled from one star.

“It just reminds us of the beauty of our universe, and the ongoing activity,” says Jennifer Wiseman, a NASA astrophysicist and the senior project scientist for the Hubble Space Telescope.

It’s hard to overstate—or even state—how deeply Hubble has transformed astronomy with its eagle eye. Free from the blurring effects of Earth’s atmosphere, the telescope can do the equivalent of spotting clouds of fireflies in Tokyo from Washington D.C., or seeing an individual human hair from a mile away. Ground-based telescopes struggle to reach a tenth of that precision.

And the telescope has used that vision to observe the universe near and far. Astronomers have used Hubble to discover possible geysers of water on Europa, take videos of auroras on Jupiter, snap pictures of exoplanets around other suns, watch stars and gas whip around black holes, and clock the expansion of the universe. “It’s rewritten the textbook in every area you care to look,” says Mark Clampin, NASA’s Director of the Sciences and Exploration Directorate.

It’s a remarkable legacy, especially considering that the wunderkind observatory started off its career in ignominious failure.

A nearly eight-foot mirror lies at the heart of the spacecraft, expertly ground to exquisite smoothness. But tragically, it’s the wrong shape. During manufacturing, engineers measured its curvature with two different tools, one older manual instrument and a newer laser-based device. The first indicated that the mirror was flawed while the second suggested it had the right form, and rather than investigate the disagreement the team chose to believe the high-tech doohickey. “If you’re over budget and behind schedule and people are mad at you, there’s a temptation to talk yourself into an answer you like,” said astronaut Kathryn Sullivan during a lecture at the Symphony Space performing arts center in New York City on Dec. 3, 2019.

The one-millimeter “spherical aberration,” as the flaw came to be called, was imperceptible to the human eye, but it wrecked Hubble’s vision. NASA knew immediately that it had a problem when their shiny new space telescope, the product of decades of planning and $4.7 billion at the time of launch, returned pictures with sharp centers but blurry halos. Astronomers ran to mathematics textbooks to find techniques to correct their data and make the best of a bad situation, while the mission became a national laughingstock. A young Jay Leno once joked on late night that the government should “shoot down” Hubble and “put the thing out of its misery.”

But NASA had another idea. Mission planners had entwined the telescope’s design with that of the Space Shuttle program, making the machine serviceable by astronauts. After three years of scrambling, the engineers designed a second mirror that could correct the aberration of the first like a pair of glasses, and a team of astronauts (including Sullivan) launched to slot it into place. The astronauts also installed a new infrared camera, starting a tradition of upgrading Hubble’s components that would span five missions. “That has left us with a new observatory every time they have visited,” Wiseman says.

So even as Hubble aged, many of its parts have gotten facelifts. Clampin says that the mirrors, supports, and many electronics boxes are original, but the solar panels, batteries, instruments, reaction wheels (for pointing), and computers have all been upgraded—some as recently as 2009. The Space Shuttle program has since ended so Hubble now flies beyond our reach. But if the telescope could somehow return to Earth, it would actually weigh 3,000 pounds more than it did at launch.

The astronomical community has put all that hardware to good use. Hubble beams down about 19 gigabytes of data every week—the equivalent of six hours of HD Netflix binging. Data from the telescope has led to more than 17,000 journal articles, with more than 1,000 publications last year. Researchers compete fiercely for access to the machine with roughly 90% of proposals being rejected.

Amongst the essentially innumerable scientific highlights, Wiseman and Clampin both single out two fields that Hubble has particularly revolutionized: exoplanet science and cosmology.

When Hubble launched, five years before the first exoplanet was discovered through indirect means, astronomers debated whether the telescope would be able spot them directly, Clampin recalls. It’s seen a few, mostly hot young worlds still glowing from the heat of formation, but Hubble’s real success lies in capturing light filtering through exoplanet atmospheres as they pass in front of their star. This technique, which didn’t even exist when engineers built Hubble, has since been employed to discover liquid water and perhaps even clouds on alien worlds. “If you asked anybody 30 years ago if they thought that was possible,” Clampin says, “they’d have thought you were nuts.”

But Hubble’s greatest superpower may be its ability to peer into past, because of the way the speed of light yolks distance to time. The telescope’s deep field research program has stared longer and longer at dark patches of space, zooming into tiny spots of sky to resolve the thousands of galaxies each contains. Light from the farthest galaxies took billions of years to reach us, and with intense squinting Hubble has been able to see galaxies that existed a few hundred million years after the big bang. The universe back then, at just a few percent of its current age, was a hot mess. “As you look further and further back in time, you can see more and more violence,” Clampin says. “You don’t have galaxy-looking galaxies anymore. They’re all train wrecks,” tearing through each other at high speeds.

Cosmologists have long understood that getting from the smooth soup produced by the big bang to today’s lumpy universe of stars and planets involved a lot of growing up. But Hubble has been able to produce direct images showing exactly how galaxies have matured over the eons, helping researchers measure the age of the universe and discover the expanding influence of dark energy. It’s the difference between assuming your friend must have had some wild college years, and then getting access to their photo library. “That’s been something Hubble has really helped us understand,” Wiseman says. “How the universe has changed and progressed over time to being the life-friendly place that we enjoy, at least on one planet.”

As astronomers move into the fourth decade of the space telescope era, they look forward to a host of new discoveries from instruments young and old. After its 2009 servicing, Hubble remains at the top of its scientific game, and Wiseman expects that it may live to see its 40th anniversary.

Soon joining Hubble in the sky, possibly even next year, will be the highly anticipated James Webb Space Telescope (JWST), which will complement Hubble’s abilities with more reflecting area to collect light and an ability to see a wider variety of infrared colors. Astronomers expect the JWST will detect new elements in exoplanet atmospheres (including, just maybe, cocktails indicative of alien life), as well as even younger galaxies.

Looking farther ahead, the launch of the Wide Field Infrared Survey Telescope (WFISRT) in the middle of the decade could let cosmologists study the distant past more broadly. “Think of the Hubble deep fields as at little thumbnails,” Clampin says. “WFIRST will give you the full HD TV view of these regions.”

These up and coming space telescopes will build on Hubble’s legacy, but they will also be products of it. Clampin, who has been deeply involved in the assembly of the JWST, says that engineers now insist on getting identical mirror measurements from at least two different tools as to not repeat Hubble’s mistake. They’ve even had to ask companies to build them custom devices just for that purpose.

As NASA’s growing fleet of space telescopes continues to expand our view of the universe, one unforgettable motto of the Hubble era will undoubtedly live on: Measure twice, launch once.

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‘Oumuamua shattered astronomers’ expectations when it streaked past the sun in 2017. It was skinny, not round. It looked rather dry with ruddy hue—nothing like the ice ball it should have resembled. To make matters worse, it jetted away as if it were moving under its own power. The first interstellar object to be spotted in our solar system exploded researchers’ assumptions about what sorts of bodies are most likely to escape their host star, and how. Three years later, they’re still trying to figure out where they went wrong.

New results based on computer simulations, which appeared Monday in Nature Astronomy, aim to tie up all ‘Oumuamua’s mysteries into one explanatory package: once upon a time, a distant star shredded a comet or planetary fragment, spraying thin comet-asteroid hybrids out into the void. If the theory proves accurate, then ‘Oumuamua represents just one of a countless number of such objects, ejected by similar stars across the galaxy.

“We are confident that this scenario we proposed is common,” says Yun Zhang, a researcher at the Observatoire de la Côte d’Azur in France and co-author of the work. “We expect we will see more things like ‘Oumuamua in the future.”

Astronomers have been anxiously awaiting the first signs of an interstellar interloper for the better part of a decade, but it wasn’t supposed to look anything like ‘Oumuamua. It was supposed to be a comet—a dusty snowball that would cast off a dramatic tail as it melted in the sun’s glow. Comets in our solar system follow looping orbits that push them right to the edge of the sun’s domain, where the slightest gravitational nudge could knock them free. (Nature obliged this intuition last year when Borisov—a classic comet—became the second interstellar object to be discovered in our solar system. It has since sizzled into pieces after swinging around the sun.)

‘Oumuamua looked more like an asteroid, the other type of small body common in the solar system. These pebbly sand piles are dark and dry, with little water or ice for the sun to mess with. Numerous attempts have failed to find signs of a tail behind ‘Oumuamua, although it did inexplicably speed off as if being pushed by a jet of gas. What was driving its hasty retreat? And if it was an asteroid, which tend to huddle close to their host star, what had kicked it out into space?

Neither the “comet” nor the “asteroid” label fit well, suggesting that something new had formed around ‘Oumuamua’s host star. Guesses ranged from alien spaceship to fluffy ice cloud. “It’s really a mystery,” says Matija Ćuk, an astronomer at the SETI Institute. “We really don’t understand it.”

In late 2017, Ćuk suggested that a phenomenon called “tidal disruption” could have birthed the cigar-shaped object. Tidal forces lie behind gravity’s ability to distort a body, such as when the moon stretches the Earth’s girth, resulting in the daily rise and fall of oceans against the shore. They’re also one of the many ways a black hole could kill an astronaut, stretching her out like a piece of spaghetti. Ćuk proposed that a similar event could have shredded an entire planet into ribbon-like strands, and that ‘Oumuamua was a piece of flotsam from one such Armageddon.

Zhang’s work took Ćuk’s idea further, fleshing it out with physical details to see if it was possible. She and a colleague modified a popular simulation that considers how the particles in an asteroid-like object—which she likens to “a sandcastle floating in space”—rearrange themselves when poked and prodded by gravity. They took a variety of objects and repeatedly hurled them at a digital star until they got a sense of what might have happened to ‘Oumuamua.

It probably started out life as a comet, Zhang says. A planet or baby planet is also possible, but those objects would be less likely to match ‘Oumuamua’s inferred composition. As the comet swung by its host star, which was perhaps half as massive as the sun, it received a tidal death squeeze and got shredded. Zhang also analyzed the fragments with a heat model, and found that the host star’s warmth would have baked the surface of each fragment into a dry and crispy crust. The same squeeze would have sent some splinters, including ‘Oumuamua, flying out into interstellar space.

While she set out only to explain the ex-comet’s shape, Zhang was surprised to find that the theory could also handle ‘Oumuamua’s bizarre acceleration. Upon arrival in our solar system, additional heat from our heavier, brighter sun reached deep through the crust and liberated residual ice, the thinking goes. Those evaporating materials then gave the object a push as they escaped unseen into space. “Our analysis showed that the simulation can explain all of ‘Oumuamua’s features,” she said, its dry asteroid-like appearance as well as its comet-like activity.

The researchers can’t be sure that this precise sequence of events definitely produced the collection of rubble that passed through three years ago. But if the process plays out as easily as the simulation suggests, interstellar space could be littered with a truly incomprehensible number of such shards. Each solar system could spew out one hundred trillion ‘Oumuamua-like objects, Zhang estimates.

For other researchers, however, ‘Oumuamua remains enigmatic. Ćuk says that it’s nice to see a simulation confirming that tidal disruption can roll cigar-shaped bodies, but wonders how often stars can really tear up their comets. “If you shred one planet you get a lot of mass,” he says. “If you’re playing with comets, you need to shred something like 10 earth masses per star, which is basically all of [the comets].”

Zhang also points out that the whole theory rests upon the assumption that ‘Oumuamua is long and skinny. If the object is more pancake than sausage, as one analysis suggested last summer, the whole tidal origin story falls to pieces.

The scout is currently zooming past Uranus, beyond the reach of any telescope, so researchers will never know for sure what ‘Oumuamua looks like or how it formed. But the Vera C. Rubin Observatory, which is slated to begin sweeping and regular surveys in 2022, should spot one interstellar object each year, according to Ćuk. Only then will astronomers be able to get a sense of what sorts of objects are whizzing around out there. “Before you do physics, you do stamp collecting,” he says. “Let’s see what else falls out of the sky.”

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There’s a giant blank spot in researchers’ ever-growing map of the solar system. Over the last two decades, a veritable fleet of probes has measured quakes on Mars, scrutinized the grooves in Saturn’s rings, observed jet streams on Jupiter, and heard the heartbeat of Pluto. But in terms of up-close-and-personal exploration, our image of Uranus hasn’t advanced substantially beyond the featureless blue beachball captured by Voyager 2’s vintage instruments in 1986.

But last year, while combing through NASA’s archives, two planetary scientists noticed something earlier analyses had overlooked—a blip in Uranus’s magnetic field as the spacecraft cruised through a magnetic bubble of sorts. The new result, which appeared last summer in Geophysical Research Letters, comes as planetary scientists start to shift their focus to some of the field’s deepest outstanding mysteries.

“The Cassini mission [to Saturn] is over and people are starting to say, ‘ok what else can we do,’” says Heidi Hammel, a planetary astronomer and the Vice President for Science at the Association of Universities for Research in Astronomy. “People are turning their sights back to these other planets and brushing off the old data.”

Gina DiBraccio and Daniel Gershman of the NASA Goddard Space Flight Center are two such researchers. Motivated by the community’s growing interest in the outermost planets, they spent hours manually processing the thirty-year-old data in a new way. Voyager scientists calculated the strength of the magnetic field as a whole, DiBraccio says, so short variations in the magnometer reading were simply considered a nuisance. But while zooming in on those jagged hops and dips, DiBraccio and Gershman spotted a special 60-second long section of Voyager 2’s 45-hour flyby where the field rose and fell in an instantly recognizable way. “Do you think that could be… a plasmoid?” Gershman asked DiBraccio, according to a NASA press release.

Plasmoids are charged globs of atmosphere blown out into space when the solar wind whips around planets. Losing such blobs can dramatically transform a world over a long period of time, and studying them can provide insight into how planets live and die. Researchers have spotted them pinching off from various planets, but the magnetic belch Voyager 2 sailed through was a first for Uranus. “We expected that Uranus would likely have plasmoids; however, we didn’t know exactly what they would look like,” DiBraccio says.

Now that they’ve caught one red handed, she says it looks quite similar to those seen leaking from Saturn or Jupiter but stealing away relatively more mass. (This plasmoid formed a cylinder roughly 22,000 times larger than Earth).

More such discoveries could remain in the archives, awaiting novel analyses. “Most of the Voyager 2 data are available on NASA’s Planetary Data System,” DiBraccio says, “and there is likely much to still be learned.”

Uranus in particular keeps on begging for further investigation. In 2014 Erich Karkoschka, an astronomer at the University of Arizona, revisited Voyager 2’s images with modern processing techniques. By blending 1600 images and sharpening the contrast, Karkoschka’s work revealed that a gumball world painted with candy-stripe clouds had been hiding within the bland blue ball all along.

On top of its unappreciated complexity, it’s also the odd planet out. Where others spin, Uranus rolls, tipped on its side with its poles pointing generally toward or away from the sun. Its magnetic field is bonkers too, offset from the planet’s center and tipped at a wild 60 degrees to the side. Planetary astronomers are blind to that magnetic field from Earth, although the Hubble Space Telescope can occasionally catch an indirect glimpse via Uranus’s auroras—which can shine far from the poles.

The Voyager team initially assumed the magnetic wackiness was linked to the Uranus’s belly flop position, but when the spacecraft flew by Neptune (which stands up straight) three years later it saw the same apparent mismatch between the planet and its field. Now researchers assume that something about the worlds’ inner workings must set their magnetic fields apart. “Boy would we like to be able to refine that theory,” Hammel says.

The next generation of planetary scientists might get to do just that, as interest in sending a dedicated probe to Uranus or Neptune is growing. Rough sketches of possible missions were published in 2018 and early last week. And DiBraccio says more such proposals are on the way. The general dream is to send a Cassini-style orbiter that will circle one of the planets for years, surveying its magnetic field and studying its heat flow. The spacecraft would also carry at least one smaller probe to fire into the atmosphere. There, it could measure otherwise invisible gases leftover from the planet’s formation.

And if the orbiter targets Neptune, it can schedule trysts with the enigmatic moon Triton (not to be confused with Saturn’s Titan). Likely an ex-dwarf planet Neptune plucked from the largely inaccessible realm ruled by Pluto and other frozen bodies, Triton may harbor an underground ocean.

Understanding the outer reaches of our solar system has never felt so urgent. NASA tends to plan its planetary priorities decade by decade, and they’re currently picking targets for the late 2020s and early 2030s. Meanwhile, between the last so-called “decadal survey” and the current one, exoplanet science has exploded, and Neptune and Uranus have become more than just local oddities.

Researchers now know that similar “Sub-Neptune” worlds are the most common type of planet in the galaxy. And many of these worlds are likely “ice giant” planets akin to our big blue duo. Unlike the gas giants, which are mostly hydrogen and helium, these planets are largely made from heavier molecules such as water and ammonia. If researchers want to understand what makes these worlds so common in alien systems—and why our solar system is such an oddball—they’ll have to figure out everything they can about Uranus and Neptune.

But our cosmic backyard is vast, and getting out toward the fence will take time and extensive planning. The sun shines too dimly out there for solar panels, so nuclear power is the only option for a years-long mission. And billions of miles is just really far away. “Even with our current best rockets and gravity assists, it’s still a decade to get out there,” Hammel says. Between technology development and mission design, she hopes to see a probe launch even if she doesn’t get to work on the data it will someday send back to Earth. “Most of us tend to think in multidecade time scales,” she says.

Proof of Uranus’s plasmoids sat buried in Voyager 2’s data for thirty years before DiBraccio and Gershman happened upon it. The next ice giant encounter might not take place for twenty years, and any researchers that may someday glean additional insights from its legacy data likely haven’t even been born yet. Imagining what sorts of discoveries might lie ahead gives astronomers like Hammel a uniquely long-term perspective. “I dream about exploring Uranus and Neptune and I dream about fantastic space telescopes,” Hammel says, “That’s how we get through tough times. We dream about the future.”

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If any beings live in the solar system HD 74423, their young ones would sketch daytime scenes quite differently than human children do. Where we draw one sun, they’d draw two. And where we draw our star as a round orb, they’d likely draw one of their suns as a bulging teardrop. Gifted animators might even capture the bump’s motion as it stretches toward and recedes from its companion over a matter of hours.

This star’s outlandish shape and behavior are prominent enough to be detected from Earth, 1,600 light years away, astronomers announced on Monday with a publication appearing in Nature Astronomy. Theorists have long suspected such a system was possible, but HD 74423 is the first confirmed binary containing one star whose pulses reach out toward its partner. And because it represents a new way for two stars to interact, it could also help astrophysicists better understand what makes some stars ripple and contort while others stay largely motionless.

“Wow,” wrote Gerald Handler, an astronomer at the Nicolaus Copernicus Astronomical Center in Poland in an email to a colleague upon first seeing data containing the flickers of the bulging star. “I have never seen something like that before.”

Our sun appears pretty unchanging day after day, but that’s because we’re looking at it from so far away. Up close, boiling blisters on its surface reveal the star’s more variable, liquid side. Other stars experience internal churning and bubbling too, and under the right circumstances they can positively pulse with activity. (The field of asteroseismology uses these reverberations to infer what’s going on deep beneath a star’s surface.)

One dramatic case of stellar throbbing is the type of star known as a “heartbeat star.” They occur in pairs with elliptical orbits that bring the two stars alternatively nearer together and farther apart. When the partners draw close, they give each other an extra gravitational squeeze that then relaxes as they pull away. Overtime these regular squeezes cause one or both stars to undulate—stretching out like an egg and then collapsing back into a squat orange-like shape.

HD 74423, the new discovery, is a pair of stars that whip around each other in a roughly circular orbit once every 38 hours. They keep a pretty constant distance from each other, Handler says, which means they don’t fit the definition of heartbeat stars. Their behavior is even weirder.

Since the partners orbit each other so closely, one partner’s gravitational pull drags the surface of the other toward it, stretching the star out into a persistent teardrop shape. And the teardrop pulsates inward and outward toward the companion. In an upcoming publication, the astronomers will propose that this pulsation takes place because the tapered part of the star is “fluffier,” Handler says, and this fluffiness amplifies natural ripples from deeper in the sun in the direction of the partner.

Astrophysicist Donald Kurtz of the University of Central Lancashire in the UK first predicted that such a setup might be possible decades ago, but no astronomer had located one until now. “I’ve been looking for a star like this for nearly 40 years and now we have finally found one,” Kurtz said in a press release.

And they almost didn’t find it. NASA’s Transiting Exoplanet Survey Satellite (TESS), which focuses on looking for exoplanets, made the discovery possible. In HD 74423, the companion star blocks light from the teardrop star much as an exoplanet might, but not similarly enough to get picked up automatically by NASA’s planet-hunting algorithms.

Instead, two volunteer citizen scientists—Robert Gagliano and Tom Jacobs—independently noticed anomalous flickers in the light coming from HD 74423 as the teardrop grew, shrunk, and turned. They flagged the system as a potentially interesting target, and Handler confirmed the details by observing it more closely with the South African Astronomical Observatory. “Without those guys we probably would never have found it,” he says.

And now that they have it, the next step is to look for more. While this case is largely an astronomical curiosity, finding other pulsating teardrop stars could help answer a larger question in the study of stellar vibrations: why do some stars quake while others remain still? Even in the twin stars of HD 74423, only one appears to be quivering. Astronomers would also like to figure out more about how much oomph is required to orient the pulsations in a given direction, and what the system will look like in billions of years—all questions that require deeper insight into the structure and behavior of the balls of plasma that dot our universe.

“We just need to keep looking,” Handler says. “We have more questions right now than answers.”

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Somewhere in the constellation Auriga, a world is ending. Fortunately, WASP-12b is an inhospitable planet, so all casualties will be limited to gaseous explosions of apocalyptic proportion. Despite possessing twice the waistline of Jupiter and half again its heft, this giant exoplanet lives so close to its star that it whizzes around once each (Earth) day. It also appears darker than fresh asphalt, trapping almost all of the light that falls on it as heat.

Being this hot, swift, and dark comes with a downside: Under such conditions, the atmosphere burns so intensely that it can’t quite keep itself together. “The planet is so hot that the outermost layers are pumped up,” says Samuel Yee, an astrophysicist at Princeton University. Eventually parts of the planet’s atmosphere expand so far from its core that they fall into its hungry host star. In 2010, researchers gave the planet just ten million years left to live.

But according to new research, WASP-12b may not even have that long. As it wastes away to nothing, a separate gravitational effect also drags the world toward its star, which will rip the planet apart in perhaps 3 million years, Yee and his colleagues argue in their latest paper. Astronomers have long suspected that such planets, appropriately known as “hot Jupiters,” should be especially prone to this fate, but WASP-12b’s death spiral is the first to confirm it.

Researchers discovered WASP-12b in 2008, as its passage in front of its star dimmed the host’s light, causing a daily flicker. Follow-up observations also revealed that the planet’s heat makes it glow, letting astronomers tell when it disappeared behind the star as well.

After years of scrutiny from multiple teams, astronomers noticed that the star wasn’t flickering with perfect regularity. Rather, the sun started to dim earlier and earlier. Researchers initially wondered if a second, unseen planet was mucking with WASP-12b’s orbit, but after further observations the community settled on two possibilities: either the planet traced out an oval path, and the tips of that oval were also advancing slowly around the sun, or the planet was getting closer to its star, and its orbits were getting shorter.

The new research, which appeared in The Astrophysical Journal Letters, settles this debate. The researchers report new data from ten transits (which happen when the planet passes in front of the star) and four “occultations” (when it slips behind). If WASP12-b’s orbital oval were turning, the timing of the planet’s disappearances would evolve differently from those of its transits, because a planet’s speed changes more in an elliptical orbit. By combining their new data with a historical catalog of around 160 transits and occultations, Yee says, the team showed that both events are happening earlier and earlier—a nearly sure sign that the planet’s path shrinks with each new orbit.

The observations suggest that each Earth year, the planet orbits the star about 30 milliseconds faster. Over the course of this past decade, those imperceptible accelerations have accumulated, shifting the onset of WASP-12b’s transits by more than seven minutes overall, Yee says. He and his colleagues predict that in the next three to three and a half million years (a blip in the billion-year lifetime of the system), the planet will dive so close to its star that the increased intensity of gravitational forces will tear it apart.

WASP-12b’s impending demise marks a first for exoplanet astronomy and presents a rare opportunity to peer inside a star by studying its tides.

This alien planet is falling toward its star for the same reason that our moon is moving away from Earth. As the moon gravitationally stretches our planet, it raises the oceans around the equator, creating a tidal bulge. The Earth spins faster than the moon does, so this swell sits a bit ahead of the moon. All objects attract each other gravitationally, and the additional bulk from the higher oceans act as a carrot in front of the moon, spinning it faster and pushing it into a higher orbit. Because of this effect, the moon moves an inch or two further out into space each year.

The WASP-12b is big enough and close enough to its star to act as the moon does to Earth, raising a tide in the stellar material itself (tides stretch the entire planet, land and sea, into a slight, football-like shape. The shift is only noticeable to us in the oceans, though). The star spins much slower than the planet though, so the tidal tango plays out in reverse. The star’s bulge lags behind WASP-12b, slowing its rotation and dragging it inwards into a lower orbit.

While the Earth’s bulging depends on how its oceans rub against the ocean floor, the exact structure of tides on WASP-12b’s yellow dwarf star remains mysterious. “In the star there’s no ocean or surface, so what’s actually going on,” Yee asks.

Some sort of stellar waves must be brokering the transfer of energy from the planet to the star, he says, so measuring WASP-12b’s spiral more precisely will help researchers get a handle on the internal structure of its host star. The planet’s current three-million-year prognosis is already about 10 times shorter than simple calculations predict, indicating that the star may be running out of fuel and entering the final stages of its life.

In the bigger picture, Yee and his colleagues wonder whether tidally induced spirals have killed off other exoplanets. Research from last year has shown that stars hosting hot Jupiters tend to be young, perhaps because older stars have already destroyed their planetary companions. Other researchers speculate that the abundance of heavy elements in some stars could mark the final resting places of dead planets, Yee says. Only further observations of other close orbiting giants will help scientists better understand their fates.

“This is just one particular planet around one particular star,” Yee says, “but as we get more examples we can understand if this is a weird situation or if most [hot Jupiters] end up like this.”

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With each new alien planet discovered, the astronomical catalog of bizarre worlds and systems swells. “Hot Jupiters” huddle closer to their host stars than Mercury. “Circumbinary” planets circle two stars at once. One “super earth” is blanketed in a layer of water so hot that it acts as both liquid and gas simultaneously. And about a dozen planets (of the thousands discovered so far) seem impossibly light for their gargantuan proportions.

“We knew they were low density,” said Jessica Libby-Roberts, a graduate student at the University of Colorado Boulder who studies these wispy worlds, in a press release. “But when you picture a Jupiter-sized ball of cotton candy—that’s really low density.”

Exoplanet researchers know these lightweights as “super puffs” because of their extremely low average density—less than one tenth of one gram per cubic centimeter. That’s quite similar to the density of cotton candy, and more than a dozen times airier than the gas giant Jupiter. This airiness likely comes from a puffed-up atmosphere extending much farther out into space than the atmospheres of rocky planets or most gas giants. However, this excess fluff poses problems for theories of planetary formation. A 2016 proposal suggested that such worlds were born in icy realms far from their suns, where cooler temperatures could speed the amassing of their oversized atmospheres, before moving inwards to where current candidates have been observed. Now recent research, soon to be published in The Astronomical Journal, uses new Hubble observations to check one prediction of that theory—that the ice accumulated during their formation should persist as water in their atmospheres today. But the search came up short, forcing a re-interpretation of the fluffy worlds.

“We expected to find water, but we couldn’t observe the signatures of any molecule,” Libby-Roberts said. “It definitely sent us scrambling to come up with what could be going on here.”

The researchers pointed the Hubble Space Telescope at star Kepler-51 as two of the system’s three super puffs took turns passing in front of it, recording the resulting dimming in various colors of light. Different molecules—such as water—block light in different ways, so if a planet looks bigger or smaller when viewed in certain wavelengths, astronomers can infer the molecular ingredients in its atmosphere.

Kepler-51’s super puff duo, however, appeared the same in each of Hubble’s observations. This monotony could indicate that only bone-dry hydrogen and helium fill the planet’s voluminous atmospheres—but that conclusion would clash with how such worlds likely form. Rather, the researchers suggest that thick grey clouds cloak the planets. Those could block the more varied light from the lower layers, which might contain the water traces they were searching for, from reaching Hubble. Libby-Roberts likens the cloud cover to that of Saturn’s moon Titan, which is entirely enveloped by a yellow haze.

“If you hit methane with ultraviolet light, it will form a haze,” Libby-Roberts said. “It’s Titan in a nutshell.”

If the super puffs truly are as candy-like as they seem (errors in measuring their mass would resolve the mystery in another way, the authors note), they won’t stay fluffy forever. The Kepler worlds orbit so close to their star that its energy must be blowing billions of tons of fluff out into space each second, the researchers calculated using a model. At that rate, one of the planets will naturally mature into a more common type of exoplanet, a “sub-Neptune,” in about five billion years. The other will remain usually light, but lose its super puff status. The Kepler-51 system, the researchers write, may represent a snapshot of mini Neptunes and oversized Earths in their “teenage” years (which for planets means their first billion or so years of life).

Alternatively, other researchers wonder if this class of planet may be nothing but a sweet dream. Earlier this year, the researchers behind that 2016 puff-ball formation theory raised the possibility that the planets could be belching out clouds of dust, inflating their apparent size. Or the long dips observed by Hubble and other telescopes as the planets pass in front of their star could originate from Saturn-like rings, which would similarly exaggerate the worlds’ true sizes. Another team considered this theory in November, and found that it matched some of these mysterious planets, but not others.

To dig deeper into the fluffy worlds, researchers are waiting for the upcoming James Webb Space Telescope. After launch, currently planned for 2021, the instrument’s keen eyes should be able to discern enough detail in the dimming of Kepler-51 and similar host stars to distinguish between alien ring worlds, dust streams, and super puffs.

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Someday, our sun will swell into a red giant and scorch everything in its path before collapsing into a white-hot dwarf star. In solar systems with stars like our own, this apocalypse tends to wipe out any inner planets. But whatever survives has a shot at enjoying a second act, astronomers recently confirmed.

White dwarf stars, burnt out cores light enough to avoid collapsing into neutron stars or black holes, pepper the Milky Way. At least some should host exoplanets, considering their previous lives as normal sun-like stars, but no one has ever detected a white dwarf solar system. But now, researchers think they may have found one through careful astronomical detective work. A puzzling chemical footprint many hundreds of lightyears away suggests the presence of a white dwarf that’s feeding on the atmosphere of a nearby planet.

“It’s such a unique composition that I think it has to be related to some type of planet,” says Boris Gänsicke, a physicist at the University of Warwick in the UK and co-author of the research, which recently appeared in Nature, “and because of its atmospheric material, it has to be a planet with a very large, very deep atmosphere.”

On top of proving that at least some planets out there have a post-red giant future, the first-ever detection of a white dwarf planetary system also showcases a new technique for investigating the atmospheres of exoplanets.

Amidst thousands of white dwarfs spotted by the Sloan Digital Sky Survey, this star—which sits 1500 to 2000 light years from Earth in the direction of the constellation Cancer—looked odd from the beginning. Like many others, this telescope can measure an object’s chemical makeup by studying the colors of light it emits. An excess of light from hydrogen suggested that it was sucking the gas from a companion star, but Gänsicke also noticed a hint of light shining from oxygen atoms—a rarity in stars.

To take a closer look, he and his team won four hours of prized observing time on the Very Large Telescope (VLT) in Chile, one of the world’s most powerful telescopes. Within the first half hour, he knew they were onto something big. VLT’s keen eye clearly picked out photons originating from both oxygen and sulfur atoms, something Gänsicke and his colleagues had never seen before. “It was exceptional,” he said. They could also tell that the star wasn’t naked, but sat clothed in a rotating disk of gas, which also contained hydrogen, oxygen, and sulfur.

The group first considered the usual suspects. Could the three out-of-place elements be streaming off a nearby star? Unlikely. A companion would tug the white dwarf back and forth, and it looked pretty steady. What about local asteroids, or wreckage from past Earth- or Mars-type planets? Such small rocky bodies are rich with calcium, magnesium, and iron, Gänsicke says, but the astronomers saw no sign of such minerals.

The dwarf’s bizarre light had the team stumped, until they started thinking about the ingredients that go into making big planets. Gänsicke’s big break came while skimming a textbook about our solar system’s chemistry. Dig deep into icy giants like Uranus and Neptune, he read, and you’ll find layers of water ice (hydrogen and oxygen) and hydrogen sulfide ice (hydrogen and sulfur). Suddenly, the white dwarf’s unusual elements made sense: They were coming from the disk of gas, which was boiling off a nearby Neptune analog.

While the team can’t measure the size, location, or mass of the planet directly, modeling suggests that the Neptune- to Jupiter-sized ice giant cuddles right up against the white dwarf, racing around it once every ten days. The star blasts the planet with violent ultraviolet light, which pulverizes the ice molecules in its atmosphere and blows them out into space. There, they stream behind the planet like the tail of a comet. The ultraviolet radiation pushes much of the tail out further into space, but some falls inward into the gas disk, and from there some atoms eventually spiral in onto the white dwarf itself.

As the star cools, it won’t irradiate the planet quite as hard, and eventually the stream of atoms will cease. Overall, the planet will lose perhaps a few percent of its total mass, the team estimates.

The final puzzle is how a Neptune-like planet found its way from the icy outer depths of the system into the balmy inner realm of the rocky planets, and how it escaped destruction during the star’s red giant rampage. “The most plausible thing,” Gänsicke says, “is that there is at least one additional planet in the system, maybe more.”

The group suspects that even bigger giants lurk far out. Sometime after this star became a white dwarf, a close encounter between the ice giant and one of these other planets must have sent it ricocheting inward toward the star.

Next, the group hopes to use the system to figure out exactly how Neptune-like the planet really is. Examining the atmospheres of exoplanets is a burgeoning field in astronomy, but because planets are dark, picking out specific atoms remains largely out of reach. The white dwarf and its gas disk shine directly with pilfered elements, however, making the makeup of this Neptune a bit more accessible.

Next year the Hubble Space Telescope will turn its mirror toward the system to observe the white dwarf in ultraviolet light, giving the team a good chance of spotting carbon and nitrogen. In addition to cosmic chemistry, Gänsicke also harbors hope of eventually catching a glimpse of the dynamics of the system itself, such as traces of the planet’s tail spiraling outward and away from the star. “That’s something that we will try to see if we can detect in future observations,” he says. “That would be awesome.”

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Early Tuesday morning, the 2019 Nobel Prize in Physics went to American cosmologist Jim Peebles for his “theoretical discoveries in physical cosmology,” and to Swiss scientists Michel Mayor and Didier Queloz for their discovery of an “exoplanet orbiting a solar-type star.”

The prize united two distinct fields of research—cosmology and astronomy—on the basis of the shared guiding principle of better understanding the cosmos, according to the Nobel committee. Peebles’ work in cosmology has helped define our understanding of the origin and evolution of the universe, while Mayor and Queloz’s discoveries in astronomy have helped expand our understanding of Earth’s place within it.

Nobel committee member Ulf Danielsson began his explanation of Jim Peebles’ Nobel Prize-worthy research by referencing The Big Bang Theory‘s theme song, which gets at the basic gist of cosmology: “Our whole universe was in a hot, dense state / then nearly fourteen billion years ago expansion started.”

Peebles’ work led to the realization that only 5 percent of our universe is made of “orderly matter”—recognizable things like planets and stars. The remaining 95 percent is made up of dark matter and dark energy. Nobel committee member Danielsson compares the composition of the universe to a cup of coffee: Each is filled with mostly coffee (dark energy), along with a “fair amount” of cream (dark matter). The tiny sprinkling of sugar represents the orderly matter, otherwise known as everything we can see and touch and comprehend. “This [orderly matter] is what science has been all about for thousands of years,” said Danielsson, “up until now.”

Peebles has spent the last 50 years developing theoretical tools to uncover these dark components of the universe. He was one of the first scientists to recognize the importance of the Cosmic Microwave Background, an ancient radiation discovered in the mid-1960s that has since helped scientists discern the age, shape, and contents of the universe.

“Were it not for the theoretical discoveries of James Peebles,” said committee chairman Mat Larsson, “the wonderful high-precision measurements of this radiation over the last 20 years would have told us almost nothing.”

Peebles’ contributions to cosmology are largely theoretical. But as stated by Peebles in a news conference after the announcement, “theory, in any of the natural sciences, is empty without observation.” Mayor and Queloz, the Swiss astronomers who share the physics prize, are honored for their practical observation of the first exoplanet orbiting a star similar to our sun.

In October 1995, Mayor and Queloz spotted 51 Pegasi b, which was 50 light-years away, orbiting a sun-like star in the constellation Pegasus. They found that this new planet was shockingly unlike Earth: It’s 50 percent larger than Jupiter, has a surface temperature of 1800 degrees Fahrenheit, and orbits so close to its host star that a single “year” lasts only four Earth days.

Mayor and Queloz detected 51 Pegasi using Doppler spectroscopy. When a large planet orbits a star, the star responds to the planet’s gravity by moving in a small ellipse—from Earth, it looks like the star is wobbling back and forth. As the star shifts closer to Earth, its light appears a little bluer; as it moves away it appears a little redder. This effect is the result of our changing perception of light relative to our position.

More than 4,000 exoplanets have been found in the Milky Way since that 1995 discovery, introducing us to an amazingly diverse array of gas giants, massive Super-Earths, and inhospitable Neptunian worlds.

Mayor and Queloz’s research helped to give a “new perspective on our planetary home” and unofficially kick started the now-booming field of exoplanet research, Danielsson said. Of course, many other people helped pave the way: people like Dale Frail and Alex Wolszczan (who discovered the first pulsar-orbiting exoplanet in 1992), and Bruce Campbell, Gordon Walker, and Stephenson Yang (who theorized the existence of the exoplanet Gamma Cephei Ab back in 1988), to name just a few.

One common criticism of the Nobel Prize format is that it reinforces the myth of the “lone genius” scientist. Though the much-maligned “Rule of 3” stipulates a maximum of three awardees for each field, Peebles was quick to highlight that he was not alone in his work. “Always, from the beginning, I had colleagues,” he stated during the news conference. He drew specific attention to Soviet scientist Yakov Zeldovich, who made significant contributions to CMB signal interpretation. Another notable scientist who worked to chip away at the mysteries of dark matter and dark energy was Vera Rubin, who died several years ago. (Side note: While only three women have been awarded the physics prize, Jim Peebles is the sixth “James” to receive the honor.

Science is meant to be a heavily collaborative institution, and the joint award is meant to celebrate the interaction between theoretical and practical discoveries. As the committee explained: “This year’s Nobel Laureates in Physics painted a picture of a universe far stranger and more wonderful than we ever could have imagined.”

On Wednesday, the committee will award the Nobel Prize in Chemistry.

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If you could pack a hot air balloon onto an interstellar spaceship and travel 110 light years to a certain planet orbiting a dim star in the constellation Leo, you’d have an experience not entirely unlike ballooning on Earth. The temperature, pressure, and moist air could feel quite pleasant, though you’d need an oxygen mask—and possibly an umbrella.

“It could happen that you get rained upon,” says Björn Benneke, an exoplanet researcher at the University of Montreal.

Telescopes hunting for flickering, wobbling stars have located more than 4,000 potential exoplanets in recent decades, some of which orbit in the not-too-cold, not-too-hot zone around their host star where water would have a shot at staying liquid. Others have even been found to harbor actual molecules of H₂O. The exoplanet K2-18b, however, is the first to check both boxes, according to two studies published this week. Unfortunately, a few other decidedly unearth-like characteristics make K2018b an improbable home for life as we know it. But the discovery represents an important step toward finding planets we might actually consider hospitable.

“It’s the closest we have come to detecting some kind of environment similar to the Earth,” says Benneke, who leads one of the two teams studying the planet.

Everything scientists know about this alien world comes from the way it interacts with its star. The Kepler mission first spotted the star’s dimming in 2015, and follow-up observations with the Spitzer space telescope confirmed presence of a planet twice as large as Earth in 2017. A different instrument then weighed the planet by measuring the star’s wobble, finding it to be about eight times heavier than Earth. Another three years of observations with the Hubble Space Telescope managed to capture eight more flickers of light, leading to this week’s descriptions of the planet’s atmosphere.

The key to studying the atmosphere of a planet you can’t really see is to measure how big it looks using different kinds of light. A purely rocky planet with no atmosphere would perfectly block all colors, while each type of molecule in an atmosphere blocks only particular wavelengths. The atmosphere looks opaque in that variety of light, and the planet looks bigger against the background star. K2-18b, for instance, swells when viewed in the type of light blocked by water.

“This is basically direct evidence that there is water vapor in the atmosphere,” says Benneke, whose research was published online this week, but has not yet been peer reviewed.

Another group of scientists, whose results appeared Wednesday in Nature Astronomy, came to the same conclusion using the same data. While they can’t say whether the planet has a wet or arid climate—their models forecast between 0.01 and 50 percent humidity—they say the odds of a random statistical coincidence are lower than 1 in 2,000.

But if any future explorers do find themselves floating through K2-18b’s atmosphere, they shouldn’t attempt to land. The planet’s size and weight make it rather wispy by terrestrial standards—almost all hydrogen gas with little to no solid matter for alien creepers to crawl over. While our solar system lacks a true analog, Benneke suggests that a mini Neptune might serve as a better mental image than a supersized Earth. “I would not expect any Earth-like life because of the absence of the surface,” he adds.

K2-18b’s skies may be even more familiar than the mere presence of water suggests. Benneke’s analysis detected slight amounts of light being blocked—making the planet look slightly thicker—at all wavelengths. Since the planet’s low density rules out a surface, he interprets this obstruction as a side effect of the water. “The most likely explanation is that this is actually a cloud deck of liquid water droplets very similar to the Earth,” he says. “It’s quite likely that there’s even rain.”

The other team, however, isn’t quite ready to start issuing exoplanet weather forecasts. “Our models are fully consistent with clouds,” writes Ingo Waldmann, an astronomer at University College London who worked on the Nature Astronomy analysis, in an email, “but we cannot conclusively say clouds are there or not until [we get James Webb Space Telescope] observations.” He and his colleagues checked the observations against models of both cloudy and non-cloudy atmospheres, and found that neither was a significantly better fit than the other.

In addition to lacking a surface, K2-18b also orbits a star quite different from our sun. As a small dwarf, it shines nearly 40 times less brightly, and its cooler temperature makes it more red than yellow. That’s no problem in terms of providing energy—the planet orbits much closer than Earth does, making a lap in about a month, so it gets similar warmth—but the star’s frequent flares likely bath the planet in ultraviolet radiation. UV flares aren’t necessarily a deal breaker for life, but they don’t make living easy.

The real significance of studying more exoplanets with atmospheres like K2-18b, Benneke says, is that they help answer major questions about how stars shape their planets, such as how much dwarf stars destroy the thin atmospheres around more life-friendly, rocky worlds. K2-18b’s thick atmosphere is impervious to such stellar activity, but the techniques used to study it will be invaluable as more powerful telescopes secede Hubble in the near future.

“In the overall storyline of humanity finding life across the universe,” Benneke says, “this is maybe the furthest we have come so far.”

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Astronomers’ cups have runneth over with alien worlds since NASA launched its (now retired) ­exoplanet-​­hunting ­Kepler space telescope in 2009. But sussing out which orbiting rocks could support life as we know it isn’t an exact science; our current deep-space-searching technology can’t peer closely enough to determine surface and atmospheric compositions on faraway places. Here’s what experts have managed to work out so far.

1. Confirmed planets
Orbiting bodies dim starlight as they pass in front of their respective suns, which makes the fireballs appear to flicker out at regular intervals from our perspective. Astronomers think they’ve already spotted potentially telltale winks from more than 8,000 planets but have confirmed the existence of only around half that number.

2. Rocky planets
Mass really does matter. Rocks much smaller than ours lack the gravity to hold an atmosphere, so liquid surface water won’t stick around. Anything twice our size or larger is likely to gather dust, gas, and ice, creating a barren world like Jupiter or Neptune. Orbs 0.8 to 1.5 times Earth’s radius can be both rocky and wet, and we’ve found around 1,000 of them.

3. Habitable-zone planets
Life is a Goldilocks game; too close to the sun and you roast, too far and you freeze. A few dozen worlds seem to spin in an orbit that’s just right. They could receive anywhere from half to double the radiation that hammers Earth and still harbor life, but factors like how often host stars spit plasma flares could eliminate many contenders.

4. Earth-like planets
Headlines oft herald worlds as “Earth-like,” and a couple dozen could be. But we can’t yet tell whether bodies in other star systems share crucial atmospheric similarities with our home. The closest of our planetary twins is Proxima Centauri b, roughly 4 light-years away. Current probes and scopes can’t gather the intel we need at that distance—yet.

This story originally published in the Out There issue of Popular Science.

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Astronomers have found more than 4,000 planets circling distant stars, yet none feel quite like home. Teegarden b is the right size, but it zips around its dim dwarf star in just five (Earth) days. Kepler-452 b takes a familiar 385 days to complete an orbit around its sun-like star, but appears to be a lumbering “superterran” much more massive than the rock we call home. Where, or even whether, true Earth-twins exist remains one of astronomy’s top mysteries.

While today’s space telescopes lack the ideal skillsets for spotting an Earth 2.0, astronomers are starting to get a sense of how frequently similar worlds may pop up in the cosmos. By combining the final data sets from NASA’s exoplanet spotting spacecraft Kepler with other recent surveys, a team of astronomers has calculated the strongest such estimate yet: Visit somewhere between three and three dozen solar systems, they say, and you’ll likely come across at least one Earth. They hope their results will inform the design of upcoming exoplanet hunting telescopes, as well as our understanding of the odds of life as we know it existing elsewhere.

“Is there the possibility of other life out there in the universe?” asks Danley Hsu, a graduate student at Penn State and coauthor of the research. “Trying to estimate the frequency of Earth-like planets around sun-like stars is one of the ways we can answer that question.”

Spotting that one in a handful, however, is another matter.

NASA’s current exoplanet-seeking eye in the sky is the Transiting Exoplanet Survey Satellite (TESS), which searches for the tell-tale stellar dimming that indicates a planet has passed in front of its star. Its cameras sweep across a majority of the sky, prioritizing nearby solar systems close enough for the Hubble Space Telescope and upcoming James Webb Space Telescope (JWST) to take a closer look.

TESS has already found more than 1,000 potential (“candidate”) planets, and NASA expects it to find nearly 20,000 more. Of those, perhaps 500 will be Earth-sized, but almost none will be Earth-like. Astronomers have to spot three dimmings, or transits, to be sure they’re looking at an orbiting planet (rather than a random dust cloud or flicker), so TESS’s frequent scanning gives it time to find only planets that fly around their star in a matter of days or weeks—not years.

The satellite also targets cool, red dwarf stars. They far outnumber brighter “G-type” stars like our sun, making them a great focus for a huge exoplanet haul, but they may not make friendly homes for life. To orbit inside their so-called habitable zone, where planets get just enough energy to keep water from freezing or boiling, planets have to huddle right next to the star in what we might consider Mercury territory.

Calling these dwarf star Goldilocks zones “habitable,” however, smacks of optimism. Planets there might enjoy balmy temperatures, but the nearby star would also douse them with ultraviolet radiation and solar flares that could strip atmospheres and fry emerging microbes. Organisms may find ways to eke out survival, but they would have to get creative.

NASA’s previous flagship exoplanet-hunting spacecraft, Kepler, was tuned to brighter, sun-like stars. For years it stared unblinking at the same moon-sized patch of sky, collecting the light dips it needed to identify exoplanets. After about four years, however, just as Kepler had been watching long enough to begin to catch the third and fourth transits of stars taking hundreds of days to orbit, a part needed to keep it stable broke down.

“We unfortunately missed the window,” Hsu says, “because the spacecraft died right around when we were starting to get more and more Earth-like candidates.”

The result was a catalog full of diverse exoplanets, but not a single Earth 2.0. In the absence of hard observational evidence, astronomers turned to statistical tools to count the uncountable.

Chris Burke, an astronomer at MIT who worked previously on the Kepler mission and is now involved with TESS, likens the task to conducting a census. You count whoever you can and think very carefully about who you can’t reach and why. “Your census is never complete,” he says, “you have to understand where you’re missing people.”

In the case of Hsu and his collaborators, that meant an intimate understanding of the Kepler spacecraft’s strengths and weaknesses. Looking for a dimming star is theoretically simple, but in practice you have to worry about dead pixels, false alarms, binary stars masquerading as planets, how accurately you know the size of each star, and a litany of other complications. “Each one of these little things will shape those detections,” Burke says, and you have to learn how to figure out which planets got knocked out during the detection process and which were actually too hard to see.

The Penn State team, which recently published its results in The Astronomical Journal, used an array of new data sets to make their estimate the most robust yet. Unlike previous studies, they had Kepler’s final list of exoplanets, and a complete record of tests the Kepler team did where they stuck fake planets into the data to test how well the detection process worked. They also used the latest measurements of star sizes from the European GAIA mission, as well as innovative statistical techniques. In the end, the group calculated that at least one Earth-like planet circles every 2.5 sun-like stars at best, and every 33 sun-like stars at worst. Hsu puts the odds that the actual average falls outside this range at less than 10 percent.

Burke, who wasn’t involved in this research but has published similar work in the past, called the estimate a “benchmark,” but added that other groups could continue to refine the calculation in the future. “It’s not the final answer,” he says, “but it’s certainly a step that needed to be done.”

As for when astronomers will actually find one of these Earth twins, neither Hsu nor Burke expect an imminent discovery. Hsu points out that this estimate describes the frequency of actual Earth-like planets, and that the number that happen to pass in front of their star at the right angle for us to spot them will be lower. He hopes that researchers will build next generation telescopes with these realities in mind. “We want to have a good idea about how many planets we expect to find,” he says, “so we don’t spend a couple billion dollars to design a spacecraft that has a yield of zero.”

The WFIRST telescope will replace TESS as the shiniest planet hunter on the celestial block in the next decade, looking for planetary fingerprints in the warping of stars’ gravitational fields. Researchers expect this technique to uncover hulking Neptunes that orbit far from their suns.

But for a true Kepler successor capable of bagging a true Earth twin, exoplanet hunters will have to wait at least until the 2030’s, when concept instruments such as the Large UV Optical Infrared Survey (LUVOIR) and the Habitable Exoplanet Imaging Mission (HabEx) could fly. These behemoths would attempt to snap exoplanet pictures directly by blocking out the overwhelming light of the host star. If they survive the planning stages, LUVOIR, HabEx, or something similar could be our best bet for finding out how unique Earth really is.

“We now know [Earth-like planets] exist,” Burke says. “It’s just a matter of harnessing the technologies to learn more about them.”

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Though our cosmic backyard brims with planets, few seem fit for life as we know it. Some do orbit at just the right distance for water to stay liquid, but their hothead young stars tend to douse them with radiation that would quickly snuff out most Earthly life.

Alien life, however, could still find a way. Inspired by species of coral that take in dangerous ultraviolet light and reflect it away as harmless green and blue hues, a team of astronomers recently proposed that entire marine ecosystems on exoplanets such as the one orbiting our second nearest star (after the sun) could do the same. If so, the entire planet might respond to flares from its parent star with a fluorescent glow that future telescopes could pick up.

“Imagine how it would look,” says Lisa Kaltenegger, a researcher at Cornell University and one of the proposal’s coauthors. “It’s something that’s really beautiful to think about.”

As detections of exoplanets (planets orbiting other stars) pile up, so do the candidates for worlds capable of hosting life. Proxima b lies the closest, orbiting Proxima Centauri just over four light years from Earth. Then come the Trappist planets, a family of seven living 39 light years away. All appear to have similar masses to Earth, and some orbit at the not-too-cold, not-too-hot distance from their sun for any liquid H2O to avoid freezing or boiling.

But water doesn’t necessarily make a home. Both of these suns, like 75 percent of nearby stars, fall into the category of red dwarfs. These balls of gas are smaller, cooler, and redder than our yellow sun. They also tend to be much more “active,” a polite astronomical phrase that means they likely barbecue nearby planets with massive and regular solar flares. Proxima Centauri, our particularly well-observed neighbor, blows its top around five times a year—enough to blast away 90 percent of Earth’s ozone in just five years.

Proxima b and the Trappist planets huddle quite close to their dimly sputtering stars, orbiting every 11 to 19 days. That proximity makes them both a great target for exoplanet hunters, since they pass in front of their stars quite frequently (alien astronomers would have to observe our sun continuously for at least a year to detect Earth), as well as a terrible place for Earth life to live. Without ozone to block out the sun’s ultraviolet light, not even the hearty tardigrades would make it very long. “If you or I landed there,” Kaltenegger says, “it would be very unhealthy for us.”

But life on Earth had the privilege of evolving in a relatively ultraviolet radiation-free environment (or, at least has enjoyed ozone’s protective benefits for billions of years). Species emerging in a Trappist ocean would have had to find a more creative way to survive the ultraviolet bombardment. “If we know one thing about life,” says Kaltenegger, “it’s really good at adapting to circumstances.”

Some Earth corals, for instance, have developed the ability to absorb high-energy ultraviolet radiation, and then get rid of it by emitting a visible, lower-energy green or blue glow. Similar “biofluorescence,” the Cornell team proposed in their recent publication, could be key to survival on such a planet. Kaltenegger imagines a largely water-based world widely populated by biofluorescent floating algae, for instance, putting on a coordinated light show between the host star and the ecosystem. “Huge radiation hits the planet, and then the planet—this biosphere—would actually light up in response to it,” she says.

Biofluorescent coral

And next generation optical telescopes such as the Extremely Large Telescope (its real name), which is currently under construction in Chile’s Atacama desert and expected to begin operations in 2025, might catch such alien flickerings.

Kaltenegger and her collaborator, Jack O’Malley-James, considered a plethora of hypothetical planets covered to various degrees by clouds and glowing organisms. They found that in the ideal case (no clouds, algae perfectly blankets the planet), such a planet would glow 13 times brighter after a flare. A planet with clouds blocking half of the surface and 30 percent of the surface covered with life would glow twice as brightly. By way of terrestrial comparison, clouds cover about half of our globe and biofluorescent coral span 0.2 percent of Earth’s surface.

“The really surprising thing is that you could see it,” Kaltenegger says. “We were not expecting it to be a stronger signal than vegetation would be.” (Plants also reflect light in a unique way, which is another potential sign of life).

The real smoking gun would be the detection of a flare-induced glow, as well as an atmosphere containing oxygen plus some chemical that breaks down oxygen (indicating that life is continuously replenishing the supply). Exoplanet hunters may soon find themselves with the enviable problem of having too many potential planets to investigate, and signs of either a living atmosphere or a fluorescent glow could help prioritize future observations.

Of course, the whole idea rests on a small mountain of “ifs.” If the dwarf star hasn’t stripped the planet’s atmosphere to the bone. If the planet has water. If life found a way to fluoresce away the UV radiation. If that algae was successful enough to cover a sizeable portion of the planet. Some researchers consider those ifs to be substantial obstacles, but Kaltenegger suggests that such thinking is born from human-centric impressions of these alien environments, and that she’s trying to keep her mind open.

“It’s not bad for life, it’s bad for you and me,” she says. “This [research] is just us trying to make sure we don’t have blinders on, that we use the diversity that we know of here on the Earth to look for life somewhere else.”

Editor’s Note: Prior mention of dangerous infrared light has been changed to “ultraviolet,” which is the actually dangerous light source.

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It’s time for us to get acquainted with the “Forbidden Planet.” No, not the 1956 sci-fi classic—I’m talking about a new Neptune-like exoplanet found 920 light-years away, given the moniker thanks to its inexplicably ability to exist too close to its host star.

In the world of space science, Neptune is far from a unique gem. Similar exoplanets (gas giants far bigger than Earth but exceptionally smaller than something like Jupiter) are perhaps the most common planets out there in space. But if they get too close to their host star, in an orbital zone we ominously call the “Neptunian desert,” they’re inundated with bouts of stellar radiation that evaporates their gaseous atmospheres and leaves behind a barren, shriveled up rocky core.

That’s not the case with the Forbidden Planet—formally known as NGTS-4b. It’s in the Neptunian desert, frightfully close to its host star, boasting an orbit of just 1.34 days. Yet, as researchers report in a new paper published recently in the Monthly Notices of the Royal Astronomical Society, it retains its Neptune-like atmosphere. It’s the first-ever detection of a Neptunian exoplanet defying the odds and residing cozily (relatively speaking) amongst its host star.

“As far as we are aware, it is the first exoplanet of its kind to have been found in the Neptunian Desert,” says Ed Gillen, an astronomer with the University of Cambridge and a coauthor of the new study. ”It seems as though the Neptunian desert is not completely dry, so we are now searching our data for other similar planets to help us understand whether it is greener than was once thought.”

It’s not as though the desert is barren: “we see hot and warm Jupiter-size planets, and hot and warm planets with the size of the Earth or a bit larger,” says Vincent Bourrier, an astronomer with the University of Geneva who was not involved with the study. “There are even warm Neptunes. But there are no hot Neptunes very close to their stars, hence this name of ‘Neptunian desert.’” The desert’s boundaries vary star to star, but its effects on planets is generally the same: atmospheric loss for mid-sized gas planets (unlike hot Jupiters, they don’t have enough mass to hold onto their atmosphere), turning them into bald, rocky wastelands.

The typical way scientists detect exoplanets is by watching for dips in the brightness of a star, which would happen when a planet in its orbit transits past the star from Earth’s perspective. Exoplanets like NGTS-4b—so incredibly small and so incredibly close to their stars—aren’t easily detected since the dip in brightness is so minuscule.

“Most transiting planets detected from the ground are large and hence, when they transit, they cause their stars to appear around 1 percent dimmer,” says Gillen. “NGTS-4b is much smaller, however, causing its star to appear only 0.2 percent dimmer. To detect such a small dimming from the ground is remarkable.”

Luckily, Gillen and his team had the state-of-the-art Next-Generation Transit Survey (NGTS) observing facility at their disposal. “Our telescopes are situated in the Chilean Atacama Desert, which is probably the best place on Earth to search for exoplanets,” thanks to the area’s marvellously clear skies, and absence of light pollution and radio interference, says Gillen. “We also have incredibly precise telescope machinery. Both of the aspects greatly aided us to to find this planet.”

It’s incredible to conceive of how NGTS-4b has found a way to exist so spectacularly close to its host star. A smidgen smaller than Neptune itself (okay, 20 percent smaller, but still three times the size of Earth and about 20 times more massive) it’s torched to 1,000 degrees Celsius. It’s hotter than the surface of Mercury during the day. So what’s going on here?

So far, the leading theories Gillen and his team surmise are that the planet moved into its currently neighborhood only recently, or that it once possessed a much larger atmosphere that’s actually in the process of evaporating. Its atmosphere might also just possess some strange chemistry that gives it super powers to withstand the stellar radiation.

Whatever the case, the team is eager to find more examples of gaseous Neptunian desert dwellers in order to compare situations and hone in on the reasons why an atmosphere like NGTS-4b’s could withstand such brutal conditions. The team doesn’t have much data to understand the atmosphere’s composition (the star is too faint for the transit observations to tell us anything in detail), but follow-up observations with some more powerful equipment (oh hello there, James Webb Space Telescope) might yield something useful.

The discovery doesn’t do much to move the needle in how we look for exoplanets, but as Bourrier explains, “unusual objects such as this one can tell us a lot about the processes that formed the desert,” and the potential for cosmic oases to form in these zones. And at the very least, it’s just cool to find a planet defying the odds and upending our expectations. Hot stuff, isn’t it?

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The explosion of exoplanet discoveries in the last decade has boosted our hopes of finding another world like Earth somewhere in the galaxy. But it’s also contributed to a new awareness of strange peculiarities in star systems beyond our own—where planets exhibit bizarre alignments and eccentric configurations without any good explanation. The proclivity for pairs of exoplanets to seemingly push themselves into orbits that are more irregular from one another than they ought to be, for example, has confounded astronomers for almost a decade.

Finally, it looks like we have some answers as to why this happens, and what it means for finding habitable worlds. New findings published in Nature Astronomy suggest that these exoplanet pairs often exhibit poles that are very sharply tilted, promoting an “obliquity” (the relationship between a planet’s axis and its orbit) that pushes the planets apart. Planets could experience extreme seasonal changes and harsh climates as a result, affecting their ability to sustain environments habitable to life of some kind.

From what we currently know about the orbital mechanics of planets around stars, we expect to see certain configurations. Planets and moons often fall into what are called orbital resonances, where they pass each other at the same points as they go on their separate orbits. Certainly not all planets and moons behave this way, but resonances happen more often than not. It’s not just a coincidental phenomenon—it’s physics.

But since we began discovering more and more exoplanets, astronomers have noticed that many planetary pairs in other star systems have orbital periods that defy resonances, falling into orbits that are much farther apart than expected. And none of the suspected reasons—like the gravitational effects of asteroids or excess cosmic gas—have ever stuck.

Still, we’ve always had a few clues to work with. It was already known from prior research (including observations of Jupiter’s moons and the infamously-tilted Uranus) that orbits between two bodies could be pried apart if there was enough energy being dissipated. If the planet had a close orbit to its star, then the star could raise more extreme tides on the planet, which would then be efficient at converting orbital energy into heat energy. The dissipation of that heat energy might then be enough to actually shift the planet’s orbit.

But a close orbit in itself wouldn’t explain what astronomers were seeing in many of these exoplanetary systems. Something else was contributing to the extreme tidal dissipation that could shift entire worlds. And as it turned out, that factor could very well be large axial tilts. Young planets with fresh new orbits in concentrated regions may be forced to maintain high obliquities, and in turn this causes orbits to shift much more radically than predicted. In pairs of planets, the orbits would move farther away from resonance patterns.

“Obliquities create strong tides, and tides move, or ‘sculpt,’ orbits,” says Sarah Millholland, an astronomer at Yale University and the lead author of the new study. “Up until now, the typical assumption was that close-in exoplanets have zero axial tilt. Our study suggests otherwise.”

The study is only pitching a theory, and there haven’t been any direct measurements of exoplanet axial tilts to bolster this hypothesis. But this is still probably the best explanation for what has been a decade-long mystery in the astronomy community, and the effects are nothing to scoff at. The entire endeavor of exoplanet research moves forward on the hope of finding a habitable world, and the new findings affirm the importance that certain astrophysical mechanics have when it comes to that search. These obliquities wouldn’t just disturb climates and weather patterns, but they might also result in excess heat deposition in the planet. That could make the difference between potentially cozy Earths from searing and suffocating Venuses.

“Virtually all of the planets Kepler discovered are completely uninhabitable,” says Yale astronomer Gregory Laughlin, a coauthor of the new paper. “This includes the planet pairs that we think have at least one member with high obliquity. What we find interesting going forward, however, is that many potentially habitable planets orbiting low-mass stars might be subject to the obliquity mechanism that we’ve explored.” Most notably, this includes the notorious seven-planet TRAPPIST-1 system, in which three worlds reside in the habitable zone and five in total exhibit varying potentials for possessing liquid surface water.

Laughlin emphasizes that while it’s clear having a high obliquity will have tangible impacts on a planet’s climate, it’s still a matter of debate as to how large obliquities will impact a planet’s habitability as a whole. Earth’s 23.5 degree tilt obviously doesn’t pose a problem here, but that might be sharp enough to cause disturbing effects in a star system just dozens of light-years away.

There will need to be plenty of follow-up work to actually confirm what’s happening, and it starts with actually observing and characterizing exoplanet obliquities. But without a study like this, obliquities would still be under the radar for most astronomers. “We used a theory that had been applied to somewhat obscure special cases in our own solar system, and showed that it can work beautifully in the extrasolar context,” says Laughlin.

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Adorn yourself in precious gemstones, and you’re sure to attract some attention. It’s true not just for people, but for planets as well. In the latest issue of Monthly Notices of the Royal Astronomical Society, a group of European scientists discuss the discovery of a new exoplanet rich in rubies and sapphires, leading to some exciting new questions about the kind of chemistry and conditions that give rise to such an exotic class of celestial worlds.

The new investigation comes out of a larger quest to understand how planets are formed. According to Amy Bonsor, an astronomer at the University of Cambridge and a coauthor of the new paper, the goal was to “study the composition of rocky bodies outside our solar system that have been swallowed by the remnants of stars like our sun, called white dwarfs.” These sorts of studies have shown just how prevalent materials like calcium and aluminum are in rocky exoplanets, and the team wanted to know what sorts of conditions might give rise to a planet made entirely of such materials.

That quest led the team to HD219134 b: a super-Earth located 21 light-years away in the constellation Cassiopeia, with an orbit around its star that lasts just three days. It’s a rocky planet, but that’s pretty much where the similarities with our own world end. It’s about 10 to 20 percent less dense than other Earth-like counterparts, and this seems due to enhanced concentrations of calcium and aluminum, among other element species important to gemstone creation. The planet possesses the sort of high-temperature conditions that would facilitate gemstone formation, leading the researchers to believe HD219134 b is chock full of rubies and sapphires.

And it’s far from the only exoplanet of its kind. Descriptions of previously-discovered super-Earths like 55 Cancri e and WASP-47 e retain the same sort of lighter-than-expected densities that HD219134 b does. As a result of the new findings, the team hypothesizes that “a new class of rocky exoplanets exists made from large quantities of calcium and aluminum and their oxides, and these planets formed very close to their stars,” says Bonsor. 55 Cancri e, WASP-47 e, and HD219134 b are simply the first three candidates of this class.

Overall, the findings underscore the emerging understanding “that exoplanets are truly diverse and potentially very different from our own Earth,” she says. The range of what rocky exoplanets — especially super-Earths — might be made of is actually much wider than initially predicted. “How rocky planets form has a major impact on what they are made from.”

The team plans to look for more exoplanet candidates that exhibit the same sort of chemical compositions. The PLATO mission, a planned exoplanet survey spearheaded by the European Space Agency, “will be great for finding these,” she says. “There are also few systems that are starting to appear from current searches for rocky exoplanets.” The ultimate goal is to use this line of research to model how primitive collections of these materials slowly grow and evolve into entire planets.

Life as we know it would never be able to evolve or exist on these glittering globes, but it’s interesting to understand how the worlds form. “This is something we don’t truly understand even for our solar system,” says Bonsor, and that could shed light on how a planet like Earth comes into being, and whether or not our solar system may have once been capable of nursing a granular infant into a super-Earth treasure trove of precious gems. At the very least, there’s something wickedly cool about knowing there’s another planet out there shimmering brightly with red and blue rocks.

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The huge bloom in exoplanet discoveries over the last decade gives us more and more hope we’ll soon find life on another world. While water remains the most important sign that alien life is possible, scientists look for many other chemical elements and compounds that could bolster the ability for extraterrestrial life to evolve and sustain itself elsewhere. Oxygen is obviously one such “biosignature,” given how important it is to complex life here on this planet.

But maybe we’re putting too much stock in the air we breathe. A new study published in ACS Earth and Space Chemistry suggests the presence of atmospheric oxygen on another planet is far from a sure sign.

“The presence of oxygen in Earth’s atmosphere, in significant quantities, is due to the presence of life,” says Nikole Lewis, an exoplanet scientist from Cornell University and a coauthor of the new study. While life could certainly exist without significant access to oxygen, “most of current thinking on how to detect life on other planets focuses on finding planets with atmospheres very similar to Earth’s,” she says.

However, before knowing whether a gas or a combination of gases indicates life, “we have to fully understand the chemistry happening on a planet,” says Chao He, a researcher at Johns Hopkins University and the lead author of the new paper. “Our study provides some insight into the atmospheric chemistry” and suggests certain processes could easily produce oxygen sans biology. Scientists might need to consider that oxygen could be a false flag for signs of alien life.

Naturally, this is not an easy question to investigate. He and his colleagues took advantage of Johns Hopkins’ special Planetary HAZE Research, or PHAZER: an experimental chamber that can simulate a broad range different atmospheric chemistry conditions, from the frigid surface of Pluto to the incredibly hot high altitudes of Venus. The idea is to expose precisely mixed gases to a high energy source (plasma or UV light, both of which can be emitted from a star) to see if hazes (small particles produced by photochemical reactions) will form, and if this will alter the atmosphere’s chemistry itself.

“The idea is to be able to not just simulate chemical processes happening in these atmospheres, but also vary them in a systematic way to try to understand what processes actually dominate the things we are actually able to observe with spacecraft and telescopes,” says Sarah Hörst, a professor of planetary science from Johns Hopkins University and a coauthor of the new paper.

He and his team ended up testing nine different gas mixtures that simulated predicted atmospheric chemistries on super-Earth and mini-Neptune exoplanets (the most abundant types of exoplanets in the Milky Way galaxy). These atmospheres all possessed different amounts of carbon dioxide, hydrogen, and water, and ranged in temperatures between 80 and 700 degrees Fahrenheit.

Ultimately, the team found that UV and plasma exposure altered the selected gas mixtures in such a way that they produced several different types of biosignatures—including oxygen and other organic compounds—distinctly and abiotically. In other words, they showed that living critters aren’t necessary to produce free oxygen—it could be the result of photochemistry, suggesting that oxygen may not inherently be a robust sign of life.

“It will be important for future observations that claim detections of life are able to rule out that these biosignature species are not created through abiotic sources,” says Lewis. “We should continue to investigate how it is possible to produce biologic false positives in the atmospheres of exoplanets, but also determine what combinations of observations spanning what wavelengths would allow us to rule out false positives such as these.”

The study is hampered by the fact that the chemical simulations only ran for a few days, and that the gas mixtures were based on predictions of what exoplanets might possess, rather than direct observations (which we currently don’t have the technology to make). Some of those limitations will be solved over the next decade when instruments like the James Webb Space Telescope can measure the chemical compositions of some distant worlds, but these findings are a good reminder that we shouldn’t necessarily limit ourselves to exoplanets that match an Earth-like template.

The study’s biggest implications may simply be in demonstrating just how unlikely it is we’ll be able to use a simple measurement to find extraterrestrial life. “The experiments themselves are not the final answer,” Hörst cautions, “but they are an important piece of a puzzle that includes observations, computer models, and laboratory experiments. We aren’t the first or only people to say this, but it is going to be really, really, really challenging to search for life by measuring atmospheric composition only.” She emphasizes the need to dig deeper into understanding how other factors—like volcanic activity, comet collisions, and new chemistry we’ve yet to consider—can contribute to biosignature production, even in the absence of biology.

If the truth is out there, it’s more complicated than we ever predicted.

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SAN PEDRO DE ATACAMA Visiting the Atacama Large Millimeter/Sub-millimeter Array (ALMA) is not for the faint of heart. After driving up the barren plateau to meet my guide Danilo Vidal, ALMA’s visit coordinator, the first stop was a health check. Just to hang out for a few hours at the Operations Support Facility where ALMA’s staff lives and works to solve the mysteries of the cosmos, I had to prove that my heart beat not too fast and not to slow, and that oxygen saturated at least 80 percent of my blood (at a recent sea-level physical I scored 96 percent).

But the extreme environment hasn’t stopped nearly two dozen countries from coming together to build the most ambitious astronomical tool on the planet. Getting 66 state-of-the-art antennas to operate in sync at a facility nearly as high as Everest’s base camp takes hundreds of engineers and other staff operating with military precision. Now fully functional after decades of construction and six years of upgrades, the institution is finally devoting much of its power to one of its main goals: watching for the heat glow of dust as it swirls around young stars. Already ALMA observations are rewriting the story of how those systems go from clouds of sand to families of planets, which is also the story of how Earth became the third rock from our sun.

A blood oxygen saturation of 91 percent won me clearance to carry on, although Vidal handed me a single-use canister of oxygen just in case. Then we climbed into his SUV and he hooked up his own nasal hose leading to two heavy duty oxygen tanks. “Regulations,” he said, as we started the drive up to the top of the Chajnantor Plateau, cactuses and vicuñas rolling past at the mandated 20 miles per hour.

Our eyes bias us toward the rainbow hues we can see, but many other types of light permeate the universe. Stars burn across and beyond the visible spectrum, black holes emit x-rays and radio waves, and stellar explosions shoot out rays of many varieties. Only by looking at all these different “colors” can we get a complete picture of the cosmos.

ALMA, which looks at light waves about a millimeter in length, functions as the world’s greatest set of night vision goggles. Objects emit different types of light depending on their temperature, and the observatory’s antennas let it pick out objects that aren’t hot enough to shine like stars. To its eyes, cool dust glows brightly against the frigid background of space, similar to how warm bodies shine to infrared cameras. In fact, ALMA is blind to visible light altogether, which lets it watch the skies both day and night.

The story of dust is really the story of everything we can see, which is why the astronomical communities of North America, Asia, and Europe banded together with the Chilean government and spent 1.5 billion dollars to build an observatory on top of the world’s driest mountain. Clouds of hydrogen in space collapse into stars, spinning up disks of leftover dust that eventually swirl into the planets, asteroids, and comets that make up solar systems. We can study our own cosmic neighborhood up close, but researchers ache for more diverse, younger examples to sort patterns from coincidences.

Computer models go a long way toward that goal, but there’s no substitute for images catching the planet-birthing process in action. Previous millimeter instruments lacked the necessary power, but on this front ALMA has been a game changer. “It’s rare that you get this big of a leap,” says Sean Andrews, a researcher at the Harvard-Smithsonian Center for Astrophysics. “This is like going from a little handheld telescope to the Hubble space telescope.”

At the top of the plateau I could immediately see how ALMA gets those money shots. Even without as much as a blade of grass in sight to help your brain calibrate size, the sprawling Array Operations Site looks huge. But before I could see the antennas up close, it was time for another health check. We entered what Vidal says now counts as the highest technical building in the world after a Nepalese train station stopped working last year, and I narrowly received clearance to continue the tour with 3% oxygen saturation to spare.

ALMA is an interferometer rather than a telescope, splitting its operations among 66 large dishes that span an area impossible for any single instrument—more than a mile across. That was the size when I visited, anyway—each of the 100-ton antennas is portable. Two monstrous forklifts, nicknamed Otto and Lore, lug a couple of antennas per day in an unceasing dance that, over the course of months, blows up the array to an unparalleled ten miles across. By expanding and contracting, astronomers can prioritize either detail or scope in a cosmological version of the smartphone’s pinch to zoom function. They just have to make sure the dishes stay plugged in the whole time (the forklifts have a battery system that supplies electricity). If the power fails and the internal machinery warms much beyond its operating temperature of 450 degrees F below zero, the driver will be left holding a multi-million dollar brick.

Fortunately that hasn’t happened yet. Finally at full power, the array creates images ten times sharper than it did during its 2011 debut, a resolution that increasingly allows astronomers to grasp the finer details of planetary formation.

The first step in a dust grain’s journey from “fluffy sand” to a proper world depends as much on how it communes with its neighbors as it does on the disk at large, according to Karin Öberg, the leader of Harvard’s astrochemistry group and one of five North American representatives on ALMA’s board. Laboratory work suggests that planetary seeds start by becoming sticky, gaining an ice coating through collisions with hydrogen and oxygen. Picking out specific elements from hundreds of light years away is tough, but ALMA has spotted extraterrestrial sugar and alcohol.

Growing larger than icy dust bunnies seemed theoretically impossible for years, empirical evidence beneath our feet notwithstanding. The spinning forces inside a disk should tear dust clumps apart before they can swell beyond the size of a rice grain, models predicted, unless somehow particles were gathering in special, denser areas.

A team led by astrophysicist Nienke van der Marel of the NRC Herzberg Institute for Astrophysics in Victoria, Canada snapped the first direct images of just such a “dust trap” while at Leiden University in the Netherlands in 2013, confirming decades of modeling. “People doing simulations of processes in a disk were working almost independently of observers,” she recalls. “Theory had drifted from observations and ALMA really brought that back together.”

Now the observatory’s new data has the simulators playing defense. When ALMA trained its dishes on HL Tau, a young star ringed by a dusty cloud 450 light years from Earth, it should have seen a smooth disk. Planets take millions of years to coalesce, the thinking went, and this system was barely a tenth that old. Yet the images came back in 2014 showing an incandescent red disk split by a half dozen crisp grooves—likely signs of baby planets hoovering up dust as they orbit. Now, a soon-to-be-published survey of 20 such disks led by Sean Andrews confirms that HL Tau is more rule than exception. However planets form, ALMA’s night vision is revealing, they’re doing it everywhere— and fast.

Returning to the Operations Support Facility halfway down the plateau, Vidal and I ran into two Italian filmmakers wandering the halls after failing their health check. They had two hours to wait for their second—and final—chance to pass. Vidal speculated that they’d ignored instructions to resist the temptation of coffee at breakfast.

Now safe to drink caffeine, we sat down for tea with Matias Radiszcz, a bearded data analyst from Santiago and unsung hero of this kind of operation. Radiszcz does battle with the facility’s main enemy: humidity. Even in a desert so dry that parts haven’t seen rain since the days of Isaac Newton, traces of water vapor always hang in the air. Radiszcz adjusts antennas to adapt to the humidity in real time. He also takes shifts as the Astronomer on Duty, deciding which observations to run out of the hundreds in the queue.

Between the altitude and the often nocturnal schedule, ALMA engineers have to get used to leading groggy lives, but participating in the unraveling of the Earth’s origin story makes the week-long shifts away from his family and the sleepless nights worthwhile. “The motivating thing is to be in the place where it’s happening,” Radiszcz says. “The Earth is like an oasis in the universe, and you can understand the value of humanity and the fragility that is life.”

By the time Vidal sent me on my way back to the town of San Pedro, the Atacama desert’s local oasis, the sun was just starting to edge below the horizon as the Earth spun Chile away from its rays. I hopped in the rental car and slowly drove back down the mountainside, a thin cloud of dust swirling behind me.

The reporting for this article was partially supported by a grant from the National Science Foundation.

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As of November 8, humanity has confirmed the existence of 3,837 exoplanets—quite an extraordinary feat, considering that before this decade the number was less than 500. Most, unfortunately, are hundreds or even thousands of light-years away, and it’s highly unlikely we’ll be able to study these worlds directly any time soon. But a handful are a little closer to home—including a frozen super-Earth just six light-years away, recently found thanks to a new technique for tracking and identifying exoplanets close to our neighborhood.

In a paper published in Nature on Wednesday, an international team of astronomers report finding a new exoplanet orbiting Barnard’s star, the second closest neighboring star system to Earth (after Alpha Centauri’s triple star system), and long thought to be devoid of any planets of its own. Named Barnard’s star b (or GJ 699 b), the planet is a hefty 3.2-times the Earth’s mass, with a 233-day orbit around the star itself.

It’s also a freezing hellscape, sitting far from its host star and removed from any decent chance to collect meaningful rays. The authors of the paper suspect temperatures average out to an ungodly -238 degrees Fahrenheit. That’s more than 100 degrees colder than the most frigid reading ever taken on Earth.

“I think it is a stretch to call this planet potentially habitable,” says Johanna Teske, a researcher at the Carnegie Institution for Science in Washington, D.C., and a co-author of the new paper. “It is too cold to have liquid water on the surface, which is basically the definition of the habitable zone,” the orbital region around a star where temperatures would be moderate enough for liquid water to exist. Liquid water is generally considered a crucial component in the evolution of life, or at least life as we know it.

That’s a bit of a downer, but it doesn’t sully the importance of Barnard’s star b’s discovery, which has been quite a few years in the making.

“There was a hint of a signal in the data prior to 2015, at which point more intensive observing campaigns were initiated to confirm the signal,” says Teske. A major push to finally resolve what these signals were coming from the detection of Proxima b, the closest exoplanet to Earth and one that might actually be habitable to life, even if those chances have slimmed in recent years. “Based on results from the Kepler mission, we know think many stars probably host small planets. So, why not look at the nearest stars?”

Paul Butler, another Carnegie institute researcher who worked on the investigation, calls Barnard’s star the “great white whale” of planet hunting. “For most of the past 100 years, the only technique by which astronomers could look for extrasolar planets was the astrometric technique,” in which researchers look for the host star to wobble in the plane of the sky relative to background stars. The new study moves beyond the limits of astrometric techniques and provides a glimpse into how exoplanet hunters might find more Earth-like worlds moving forward.

The investigation of Barnard’s star b was dampened by a few challenges, namely the planet’s long orbital period (which made it harder to study based on stellar transition), and small amplitude of the object’s signal. The team needed to amass a large amount of data in order to isolate the signal and study it, and ended up pouring over 20 years of data collected by seven different instruments. Altogether, it’s one of the largest datasets ever used to find an exoplanet, and part of the reason the team is more than 99 perfect confident Barnard’s star b is a planet. “The truly impressive part of this study is the amount and high quality of the data,” says Teske.

They found Barnard’s star b using what’s called the radial velocity technique, which detects and analyzes wobbles created by gravitational forces acting between star and planet during their orbital dance. Although this technique has been used plenty of times before to find hundreds of other exoplanets, it’s never before been used to find one so small and distant from its star.

What about the planet itself? Unfortunately, there’s still not a whole lot we really know about Barnard’s star b, besides the fact that it exists. “We don’t know whether Barnard’s star b has an atmosphere or even its average composition,” says Teske. And its distance from its host star makes it unlikely it could support life—at least life as we know it.

Still, that mystery goes both ways and could be reason to hold out onto a tiny bit of extraterrestrial hope. “It could be possible that the surface is a bit warmer and could host liquid forms of some molecules, maybe like methane,” says Teske. “And we know of moons in our solar system that are covered in a thick layer of ice but have liquid oceans underneath,” like Europa and Enceladus. Barnard’s star itself is an old red dwarf and not very active, with means there wouldn’t be much concern that it would be inundating any nearby planets with too much stellar radiation. And although it’s a super-Earth, it’s still in the range of planetary masses we think could support life. It’s all speculative, but the prospects of habitability on Barnard’s star b aren’t totally diminished.

Teske, Butler, and others will continue to study Barnard’s star b, and are particularly interested in using the new exoplanet as a target to test out next-generation instruments like NASA’s upcoming James Webb Space Telescope, which could actually assess whether there’s an atmosphere present or not. “Those types of observations are years down the line,” says Teske. “But personally, I’m still an ‘early career’ astronomer. I can be patient.”

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For centuries, human beings have wondered about the possibility of other Earths orbiting distant stars. Perhaps some of these alien worlds would harbor strange forms of life or have unique and telling histories or futures. But it was only in 1995 that astronomers spotted the first planets orbiting sunlike stars outside of our solar system.

In the last decade, in particular, the number of planets known to orbit distant stars grew from under 100 to well over 2,000, with another 2,000 likely planets awaiting confirmation. Most of these new discoveries are due to a single endeavor — NASA’s Kepler mission.

Kepler is a spacecraft housing a 1-meter telescope that illuminates a 95 megapixel digital camera the size of a cookie sheet. The instrument detected tiny variations in the brightness of 150,000 distant stars, looking for the telltale sign of a planet blocking a portion of the starlight as it transits across the telescope’s line of sight. It’s so sensitive that it could detect a fly buzzing around a single streetlight in Chicago from an orbit above the Earth. It can see stars shake and vibrate; it can see starspots and flares; and, in favorable situations, it can see planets as small as the moon.

Kepler’s thousands of discoveries revolutionized our understanding of planets and planetary systems. Now, however, the spacecraft has run out of its hydrazine fuel and officially entered retirement. Luckily for planet hunters, NASA’s TESS mission launched in April and will take over the exoplanet search.

Kepler’s history

The Kepler mission was conceived in the early 1980s by NASA scientist Bill Borucki, with later help from David Koch. At the time, there were no known planets outside of the solar system. Kepler was eventually assembled in the 2000s and launched in March of 2009. I joined the Kepler Science Team in 2008 (as a wide-eyed rookie), eventually co-chairing the group studying the motions of the planets with Jack Lissauer.

Originally, the mission was planned to last for three and a half years with possible extensions for as long as the fuel, or the camera, or the spacecraft lasted. As time passed, portions of the camera began to fail but the mission has persisted. However, in 2013 when two of its four stabilizing gyros (technically “reaction wheels”) stopped, the original Kepler mission effectively ended.

Even then, with some ingenuity, NASA was able to use reflected light from the Sun to help steer the spacecraft. The mission was rechristened as K2 and continued finding planets for another half decade. Now, with the fuel gauge near empty, the business of planet hunting is winding down and the spacecraft will be left adrift in the solar system. The final catalog of planet candidates from the original mission was completed late last year and the last observations of K2 are wrapping up.

Kepler’s science

Squeezing what knowledge we can from those data will continue for years to come, but what we’ve seen thus far has amazed scientists across the globe.

We have seen some planets that orbit their host stars in only a few hours and are so hot that the surface rock vaporizes and trails behind the planet like a comet tail. Other systems have planets so close together that if you were to stand on the surface of one, the second planet would appear larger than 10 full moons. One system is so packed with planets that eight of them are closer to their star than the Earth is to the Sun. Many have planets, and sometimes multiple planets, orbiting within the habitable zone of their host star, where liquid water may exist on their surfaces.

Related: In the hunt for aliens, satellites may light the way

As with any mission, the Kepler package came with trade-offs. It needed to stare at a single part of the sky, blinking every 30 minutes, for four straight years. In order to study enough stars to make its measurements, the stars had to be quite distant – just as when you stand in the middle of a forest, there are more trees farther from you than right next to you. Distant stars are dim, and their planets are hard to study. Indeed, one challenge for astronomers who want to study the properties of Kepler planets is that Kepler itself is often the best instrument to use. High quality data from ground-based telescopes requires long observations on the largest telescopes – precious resources that limit the number of planets that can be observed.

We now know that there are at least as many planets in the galaxy as there are stars, and many of those planets are quite unlike what we have here in the solar system. Learning the characteristics and personalities of the wide variety of planets requires that astronomers investigate the ones orbiting brighter and closer stars where more instruments and more telescopes can be brought to bear.

Enter TESS

NASA’s Transiting Exoplanet Survey Satellite mission, led by MIT’s George Ricker, is searching for planets using the same detection technique that Kepler used. TESS’ orbit, rather than being around the Sun, has a close relationship with the Moon: TESS orbits the Earth twice for each lunar orbit. TESS’ observing pattern, rather than staring at a single part of the sky, will scan nearly the entire sky with overlapping fields of view (much like the petals on a flower).

Given what we learned from Kepler, astronomers expect TESS to find thousands more planetary systems. By surveying the whole sky, we will find systems that orbit stars 10 times closer and 100 times brighter than those found by Kepler – opening up new possibilities for measuring planet masses and densities, studying their atmospheres, characterizing their host stars, and establishing the full nature of the systems in which the planets reside. This information, in turn, will tell us more about our own planet’s history, how life may have started, what fates we avoided and what other paths we could have followed.

The quest to find our place in the universe continues as Kepler finishes its leg of the journey and TESS takes the baton.

Jason Steffen is an Assistant Professor of Physics and Astronomy at the University of Nevada, Las Vegas. This article was originally featured on The Conversation.

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The Earth is expanding, satellite by satellite, every rocket launch carrying a piece of the planet’s crust into orbit. Should this incidental geoengineering venture continue, it will reshape our planet’s profile as seen across even interstellar distances—giving our smooth sphere a noticeable bulge.

If we’re puffing up our planet, other civilizations could be doing the same to theirs, producing a ring of satellites that we might be able to spot with telescopes we have today. That’s according to Hector Socas-Navarro, an astrophysicist at the Instituto de Astrofísica de Canarias in Spain, who gave a talk on the topic at NASA’s Technosignatures Workshop in Houston last week. Scientists have long speculated that fantastical sun-sized structures might betray the presence of technological aliens, but while a mega-solar panel blocking a distant star is theoretically easy to spot, such notions remain squarely in the realm of science fiction. Thought experiments like Socas-Navarro’s, however, show that now, equipped with better telescopes than their predecessors, researchers are taking searches for planet-level changes more seriously.

Socas-Navarro realized that one planet-scale project in particular should have a specific and visible effect. Imagine a world something like Earth but a few hundred years ahead, technologically speaking. In this world, the alien military has launched GPS satellites to help with navigation. Alien NASA and alien Google have also launched countless weather and mapping satellites to deliver real-time feeds of the entire planet. Many of these satellites sit in special spots, geosynchronous and geostationary orbits, where they move in lockstep with their planet, letting them monitor the same area all the time. Fill in those special orbits and you get a thin cylinder ringing the planet, one that, when it passes between its star and an observer (like us), casts a slightly different shadow out into space than the naked planet would alone. When that shadow sweeps by the Earth, planet-hunting satellites like the aging Kepler and newly functional TESS could witness the alien star dimming in a specific way.

Socas-Navarro published preliminary simulations in The Astrophysical Journal in March showing what that dimming would look like to modern telescopes if we were to watch such an Earthlike planet about ten light-years away. A satellite ring as thin as ours would be too sparse to see, he concluded, but Kepler could spot one about a billion times denser—a radical, but not impossible change that we could pull off in 200 years if launches continue to grow at current rates.

Plenty of people are already studying these stellar flickers, searching for something similar: a planet with natural rings. “It makes for a tricky transit, a tricky shadow,” says Masataka Aizawa, a graduate student at the University of Tokyo who found one possible Saturn cousin in 2017. He agrees that the dimming from a dense satellite belt should look unique. Natural rings spread out equatorially like a record while geosynchronous orbits form a north to south tin-can shape with vanishingly thin walls (ours currently measures just 450 feet thick), and the two geometries should cast two distinct shadows. But he still considers the paper’s suggestion, which he calls “science fictional,” a long shot. “I saw almost all of the [dimming] curves in the Kepler data, and there is no such evidence in my study,” he said.

Whether satellite-loving aliens are out there or not, running more detailed simulations of how the dimming patterns of moons differ from those of rings and satellite swarms helps all exoplanet researchers, Socas-Navarro points out. “We have to make sure we don’t misinterpret something as interesting as aliens, that we don’t mistake [them] with a natural ring or a natural moon,” he says. “If you look deeply they are different.”

While the technosignatures workshop focused on listening, not talking, Socas-Navarro’s ideas also suggest a sweeping conclusion about the nature of the first contact between two species. For decades our radio receivers and telescopes have restricted our potential pen pals to what he colorfully dubs “big brothers”—civilizations with unthinkably advanced technology. These species would be capable of engineering feats such as literally moving stars around, but recent surveys for traces of “astroengineering” have come up short.

As humanity’s capacity to observe advances, the type of civilization we can detect grows closer in nature to our own. Socas-Navarro’s satellite ring is the mark of a moderately advanced civilization just centuries ahead of us, rather than millennia. And he’s not the only one thinking along those lines. Others have proposed looking for orbital mirrors that could warm or cool a planet, something we humans have recently discussed as a potential solution to our own changing climate.

Any thought experiment about alien civilizations has to start with the only civilization we know, and compared with the technologists of the 1960s, climate change has burdened modern researchers with a more nuanced understanding of how technology can destabilize a civilization. “We are facing global problems that we didn’t have before, like global warming,” Socas-Navarro says, “so there is motivation to start global scale projects.” Based on our current experience, it’s not a big jump to wonder whether other civilizations, if they exist, have faced similar challenges—and found technological solutions.

Over the last seventy years, our machines have developed from being able to observe a civilization that controls stars to one that controls merely its own planet. And in the not too distant future, Socas-Navarro predicts, the synthesis of next-gen telescopes with the developing field of astrobiology will bring us to another tipping point. “We are not far from the transition,” he told an interdisciplinary audience of astronomers, archeologists, and anthropologists in Houston on Thursday. “In the next few decades we will be able to see ourselves at interstellar distances, and then we will become big brothers.”

Since little brothers can most easily detect big brothers, the hypothesis suggests that contact will tend to occur between species with a sizeable technology gap. Such contact between human civilizations has not turned out well for the little brother historically, but Socas-Navarro sees one potential reason for optimism.

Based on humanity’s experience with rapid development, researchers speculate that a “sustainability filter” may stop more violent species from reaching technological maturity. Expansionists that fail to check their aggressive impulses may quickly overrun their environment, triggering a technology-resetting crash, or even outright extinction.

Our current struggle to find a balance with our ecosystem suggests we could be facing just such a filter. Climate change threatens to render swaths of the planet uninhabitable by the end of the century, a blow that would derail economic and technological development. Clearing this hurdle, and finding a way for seven to ten billion people to live comfortably yet sustainably, will require that we take an active hand in managing the planet’s climate and resources. Should we reach that point, we’d be able to keep launching satellites and engage in other planet-shaping activities that could be seen from afar. By the same logic, other highly visible civilizations are also more likely to be active curators of their planets.

“They will implement changes to their planet just as a gardener will change his garden,” Socas-Navarro says.

In such a universe, most instances of first contact would be between mature gardeners and those grappling with their own unruly gardens. The likely outcome of such contact, one hopes, would be a gardening lesson.

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Nearly eight thousand light-years away from Earth, there’s a star about the same size as our sun. Like our own solar system, that distant star is orbited by a planet about the same size as Jupiter. But that’s where the similarities end. Around that planet circles a Neptune-sized gas giant, which may be the first moon discovered outside the solar system, and the largest moon ever observed.

Over the past 20 or so years, scientists have confirmed the existence of nearly 3,800 exoplanets, or planets around other stars. However, although nearly 200 moons are known to orbit planets in our solar system—Jupiter alone has at least 79—up to now researchers had not yet detected any moons around exoplanets. Their discovery was published today in Science Advances.

To look for such “exomoons,” astronomers from Columbia University examined data from NASA’s Kepler space telescope on 284 transiting planets—worlds that passed between their stars and the observatory, resulting in a brief dimming of the light of those stars. They focused on worlds that took more than 30 days to complete orbits around their stars—prior work suggested that worlds that orbited in less time were likely too close to their stars for any moons to survive.

The scientists detected anomalies hinting at a moon around the exoplanet Kepler-1625b. This gas giant is about the same diameter as Jupiter, and orbits the solar-mass star Kepler-1625 about 7,825 light-years from Earth in the constellation Cygnus the swan.

The researchers then requested and received about 40 hours of time on NASA’s Hubble Space Telescope to analyze Kepler-1625b during its 19-hour-long transit across the face of its star. Using Hubble, which is about four times more precise than Kepler, they detected two sets of telltale signs that suggested the presence of an exomoon. “We indeed conclude that a moon is an excellent explanation for the data in hand,” said study senior author David Kipping, an astrophysicist at Columbia University. (Read more about Kipping’s hunt for exomoons here.)

First, after the exoplanet passed in front of its star, the researchers detected a second and much smaller decrease in the star’s brightness 3.5 hours later. This supports a scenario where a moon trailed the planet like a dog following its owner.

Second, the astronomers found the planet began its transit nearly 80 minutes earlier than predicted. This is consistent with a picture where a moon’s gravitational tug would cause its planet to wobble from its predicted location. Although the gravitational pull of another planet could in principle also cause this anomaly, Kepler found no evidence for additional planets around this star during its four-year mission.

“It sounds like they struck gold,” said astrophysicist Sean Raymond at the University of Bordeaux in France, who did not take part in this work. “Moons are out there and findable. It’s an exciting next step in exoplanet exploration.”

The researchers estimated the exomoon, dubbed Kepler-1625b-i, is only 1.5 percent the mass of its companion planet, a ratio nearly that of Earth and its moon. However, that still means the exomoon may be gargantuan—Kepler-1625b is likely several times Jupiter’s mass, so its moon is likely about the mass and diameter of Neptune.

The size of the moon is surprising—”all the large moons in the solar system are at most about 1/10,000th as massive as their host planets,” Raymond said. The pair are so large that it “could also be regarded as a binary planet system,” said Avi Loeb, chair of Harvard University’s astronomy department, who did not participate in this study.

“The biggest things will be the easiest to find,” Kipping said. “This may not represent a particularly common type of moon system—it’s just it’s for the easiest for us to find.”

The researchers estimated the exomoon orbits about 33 million kilometers from its world. This means it may lie close enough for its planet’s gravitational pull to rip it apart. But there’s nothing like this in our solar system for the researchers to observe directly. To study the dynamics of the planet-moon pair, the researchers created computer models to see how the two might interact. “In about three-quarters of the simulations that we did, we find the moon is perfectly stable,” Kipping said. “We don’t have any reason to believe that orbit is unstable.”

Kepler-1625b orbits its star about the same distance that Earth does the sun. That puts the exoplanet and its moon within their star’s habitable zone—the area around the star warm enough for standing bodies of liquid water to survive. There is life virtually wherever there is water on Earth, so the hunt for alien life often focuses on habitable zones.

Both Kepler-1625b and its potential newfound moon are gas giants, and so cannot support the bodies of water needed for life as we know it to survive. However, “if there are additional rocky moons orbiting the large planet, they might be habitable,” Loeb said. “This is the most exciting prospect for future follow-ups on this discovery.”

The size of this potential exomoon raises questions about how it formed. Some moons, like Earth’s, are thought to have coalesced from the debris of a giant impact against their companion planet. Others, like Neptune’s moon Triton, likely started off as independent bodies only to later get ensnared by their planet’s gravitational pull. However, neither of these scenarios seems to fit this exomoon, said study lead author Alex Teachey, an astrophysicist at Columbia University—it is difficult to see how an impact against a gas giant would split off a moon, or how a moon of such size could get captured.

Another possibility is that this exomoon may have formed from the same material as its parent planet, as is suspected with Jupiter and its moons. New models of moon formation have suggested “a small fraction of moons can end up being as massive as about 1 percent of their host planet mass, which is about the case for Kepler-1625b,” Raymond said.

In the future, hunts for exomoons will likely look at exoplanets farther away from their stars than Earth is from the sun, Kipping said. These searches with Hubble or NASA’s upcoming James Webb Space Telescope may even turn up exomoons smaller than Jupiter’s largest ones, he added.

The scientists noted they are still urging caution about their find. “The first exomoon is obviously an extraordinary claim, and it requires extraordinary evidence,” Teachey said. “Furthermore, the size we’ve calculated for this moon, about the size of Neptune, has hardly been anticipated, and so that too is reason to be careful here.”

The researchers hope to use Hubble again to monitor Kepler-1625b and confirm the exomoon’s existence.

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Less than two months after NASA’s Transiting Exoplanet Survey Satellite (TESS) started its science operations, astronomers have detected two brand-new exoplanet candidates in the data sent back from the space observatory.

In a tweeted statement from NASA, MIT astrophysicist Sara Seager, a leader of the mission said: “The team is excited about what TESS might discover next. We do know that planets are out there, littering the night sky, just waiting to be found.”

Both exoplanets are still candidates, which means astronomers have yet to confirm their existance—but experts are already actively vetting the preliminary results.

The first exoplanet candidate was announced on September 19 and orbits a star called Pi Mensae, 60 light years away from Earth. It orbits its star every 6.3 days, and seems to have a density similar to water. It’s not the only planet around its star either:

Fun notes for @NASA_TESS 1st planet candidate: Pi Mensae star is visible in the night sky, the planet’s mass & radius show a water-like density (infers water / gases), and it’s the system’s 2nd known planet (the other has 10x Jupiter’s mass & orbits every 5.7 years). @TESSatMIT pic.twitter.com/tltNHbjDNb

— NASA_TESS (@NASA_TESS) September 20, 2018

The second planet candidate is closer to Earth, at just 49 light years away. This potentially Earth-sized world is also circling its star at a more breakneck speed, making a full orbit in just 11 hours.

TESS operates in a one-of-a-kind orbit around Earth, tracing an oval every 13 days that’s 232,000 miles away at its farthest point, and 67,000 miles away at its closest. During two years of these orbits, it will examine 400 times more of the night sky than any previous mission. In addition to potential exoplanets, it’s also already spotted a comet and an assortment of asteroids.

TESS is the successor to the Kepler Space Telescope, which has discovered over 2,000 confirmed exoplanets over the course of two missions, Kepler and K2. That telescope is now running low on fuel and reaching the end of its natural life. TESS will continue Kepler’s work, focusing on stars closer to home, and researchers expect it will find as many as 20,000 exoplanets before its time runs out.

Two worlds down, so many more to go.

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Astrophysicists just found a planet orbiting the star HD 26965, 16 light years away from Earth. Finding exoplanets is always fun, and the fact that this one is in the star’s habitable zone (where liquid water could exist on its surface) is a bonus. But that’s not why people are particularly psyched about the announcement.

See, HD 26965 also goes by 40 Eridani A—the star orbited by Spock’s homeworld in Star Trek. That means they found Vulcan. Ok, fine, they found a real-world analog to a completely fictional world, but you can’t blame Star Trek fans for being excited.

A star’s backstory

The star was first suggested as a possible candidate for Vulcan’s host in a 1968 collection of short stories by James Blish adapted from episodes of the iconic original series. It became canon decades later in a letter co-authored by Star Trek creator Gene Roddenberry published in Sky and Telescope in 1991 (see page five).

From the letter: “This year we celebrate the 25th anniversary of the launch of two important enterprises. One is the HK Project at Mount Wilson Observatory, where astronomers have been monitoring surface magnetic activity on EDO solar-type stars to understand our own Sun’s magnetic history. The other is the starship Enterprise on the television series “Star Trek.” Surprisingly, the two have more in common than their silver anniversaries.”

In 1966—at the same time Star Trek premiered—the HK project started looking at the light of distant stars, trying to get more information about how these flaming balls of charged gas worked. One of those stars was 40 Eridani A, a single star in a triple-star system.

They also looked at another star, Epsilon Eridani, which is frequently cited in science fiction as a distant alien homeworld. Thanks to a different, 1980 Star Trek book, Epsilon Eridani was also in contention to be Vulcan’s star. Here’s where it gets really fun: Citing the work of the HK Project, Roddenberry and three Harvard astrophysicists wrote in their Sky and Telescope letter that 40 Eridani A was the better candidate for Vulcan’s star since it was 4 billion years old (similar to Earth) while Epsilon Eridani was only 1 billion years old. A comparative infant, any planets around Epsilon Eridani wouldn’t have had time to evolve complex and advanced life forms.

We get it, you nerd. What about the actual science?

The data published in a paper in the Monthly Notices of the Royal Astronomical Society is just as cool as the sci-fi. To find this planet, the researchers looked for small changes in the star’s light that could indicate something was orbiting it.

Instead of looking for a dip in light as a planet moves between its star and a telescope (called a transit) these researchers watched the wavelengths of light coming off the star, looking for little shifts that would indicate how it’s moving relative to Earth. That gives them a general idea of how often the planet orbits its star, and how big it is.

“The new planet is a ‘super-Earth’ orbiting the star HD 26965, which is only 16 light years from Earth, making it the closest super-Earth orbiting another Sun-like star,” lead author Jian Ge said in a statement. “The planet is roughly twice the size of Earth and orbits its star with a 42-day period just inside the star’s optimal habitable zone.”

But a super-Earth isn’t necessarily Earth-like—the term refers to any planet with a mass higher than our home world’s but significantly less than the ice giants Uranus and Neptune. The researchers don’t yet know what kind of planet the real-life Vulcan is; it could be a big ol’ version of the rocky Earth, but it could also be a gaseous planet something like a pint-sized Neptune.

Without more data, we won’t know. But luckily we’re about to get more data. NASA’s TESS satellite will be looking toward that star later this year, and if the planet transits, we could get more information about its density or atmosphere.

If TESS does show that Vulcan is more like Earth than Neptune, that still doesn’t mean a bunch of green-blooded, pointy-eared aliens with an extremely advanced and logical society are hanging out on the surface. That’s incredibly unlikely. We’ll be lucky if there’s even microbial life for us to hunt down traces of. But we can still hope. Roddenberry was right about cell phones, tablets, and automatic sliding doors so clearly that means we’ve got 45 years left before we invent warp drive and make first contact. Make it so.

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For the first time, astronomers have detected iron and titanium vapors in a planet’s sky—the metals glowing hot like the filaments in a light bulb in the searing atmosphere. The strategy used to make this discovery might one day hunt for signs of life on alien worlds, researchers added.

Scientists investigated the exoplanet KELT-9b, the hottest alien world discovered yet, with daytime temperatures reaching more than 4,300 degrees C, hotter than many stars. This planet is located about 650 light years from Earth in the constellation Cygnus the Swan. It circles the young blue star KELT-9, which is nearly twice as hot as our sun. KELT-9b, which is about 2.8 times Jupiter’s mass, orbits its star roughly 10 times closer than Mercury does the sun.

KELT-9b belongs to a class of worlds known as ultra-hot Jupiters that blur the lines between stars and gas giants. The scorching heat of these exoplanets gives researchers an exceptional opportunity to analyze the ingredients of their atmospheres. When chemicals are heated, they each can give off a unique pattern or spectrum of light that can help identify them like fingerprints. The fact that such Jupiter-like worlds are ultra-hot means that atoms or molecules that might not ordinarily reach high enough temperatures in regular planets to give off light, such as iron, might emit detectable spectra.

Now exoplanet astronomer Jens Hoeijmakers at the Universities of Geneva and Bern in Switzerland and his colleagues have detected light from iron and titanium from KELT-9b. Using Italy’s Galileo National Telescope on the Canary Island of La Palma on the night of July 31, 2017, they detected the spectra of neutrally charged iron atoms and positively charged iron and titanium ions. Their results were published this week in Nature.

“It is the first time that iron and titanium have been robustly detected in the atmosphere of any planet beyond the solar system,” said study co-author Kevin Heng, a theoretical astrophysicist at the University of Bern in Switzerland.

Indeed, since none of the worlds in the solar system are hot enough to possess iron or titanium vapors in their atmospheres, this is the first time such metal gases have been detected in the sky of any planet, said astronomer Laura Kreidberg at Harvard University, who did not take part in this research. “You have to have insanely high temperatures — more like stellar temps than planetary — to get these elements in gaseous atomic form,” she said. “”It’s a very exciting result!”

The material in KELT-9b almost certainly had a common origin with its star. “Our understanding of exoplanet formation tells us that the star and the exoplanet formed from a common disk of dust and gas,” Heng said. “Deciphering the chemical composition of KELT-9b’s atmosphere will give us some chance at understanding its formation history.”

Normally, a major portion of the atoms and molecules making up a planet are hidden in clouds or deep under the atmosphere. Think of Earth—most of the molecules that make up our planet, from the core to the surface, aren’t represented in the atmosphere. In contrast, KELT-9b “is so incredibly hot, all the atoms and molecules are uniformly mixed through the atmosphere,” Kreidberg said. “We can therefore see the raw materials that the planet is made of. This planet is an unmatched laboratory for studying the building blocks of planet formation.”

While Kelt-9b is too hot to ever support life as we know it, the strategy used to detect iron and titanium in KELT-9b’s atmosphere “is the same exact technique that can be used to detect molecules interesting for biology in a future, yet-to-be-discovered exoplanet,” Heng said, such as oxygen or organic molecules. “You can say that hot exoplanets are a training ground for us to hone our techniques and prepare for the exciting targets to emerge in the coming decade.”

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If anything deserves a rest, it’s Kepler. In less than 10 years since it launched, the Kepler Space Telescope confirmed the existence of over 2,500 worlds beyond our own, more than any other observatory.

Last week NASA engineers working on Kepler found that the fuel level on the spacecraft was approaching dangerous levels, so they decided to pause science operations and move the spacecraft into hibernation mode to conserve fuel and preserve whatever data it has slready collected.

This particular 83 day campaign focused on an area of sky near the constellation Cancer and was set to observe star clusters, binary black holes, asteroids, exoplanets, and more. It got about two good months of observing in before the researchers decided to put it to sleep.

On August 2, it will move into position so that it can send whatever data it has already collected back to Earth. From there, the engineers back home might decide to boot it up again if there’s enough fuel left to start the next observing campaign.

“It’s like trying to decide when to gas up your car. Do you stop now? Or try to make it to the next station? In our case, there is no next station, so we want to stop collecting data while we’re still comfortable that we can aim the spacecraft to bring [the data] back to Earth,” Charlie Sobek, system engineer for the Kepler space telescope mission, wrote back in May.

This is just the latest in Kepler’s trials. In 2013, after two of the spacecraft’s gyroscopic wheels failed, the team working with the telescope back on Earth was unable to keep it steady and focused enough to continue taking data. Then researchers came up with a solution: use the sun to steady Kepler. Revived, Kepler was reborn as K2 and discovered hundreds of other exoplanets, scanning segments of the sky in campaigns spanning 82 days.

Given the recent decision to cut short the 18th campaign, it’s unlikely that Kepler will make it to campaign 20, the last campaign that researchers were asked to submit research proposals for, even if it does have enough fuel for a 19th. But when K2 started in 2014, the engineers only thought they had enough fuel for 10 campaigns.

As Kepler is entering its last days, another telescope’s story is just beginning. In April, NASA launched its next-generation planet hunter, TESS (Transiting Exoplanet Survey Satellite).

TESS will pick up where Kepler left off, monitoring over 200,000 stars within a 300 lightyear radius of Earth. Scientific data from that mission is expected starting January 2019, and researchers will use techniques they honed during Kepler’s missions to identify even more planets—with analysis now taking weeks instead of months or years.

One recent study, published in June, used data collected by KST to identify a potential planet orbiting a bright nearby star in just a few weeks time.

“We found one of the most exciting planets that K2 has found in its entire mission, and we did it more rapidly than any effort has done before,” Ian Crossfield, an MIT professor who led the study, said in a statement. “This is showing the path forward for how the TESS mission is going to do the same thing in spades, all over the entire sky, for the next several years.”

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Why do we have seasons on Earth? The planet’s axial tilt, of course. But the tilt does more than just push us from spring, to summer, to fall, to winter. It’s also an important stabilizing force for our atmosphere—without which life on Earth would be almost assuredly impossible. And so it stands to reason that tilt might play an important role in fostering life on other worlds as well. That brings us to some new findings, published in The Astronomical Journal, that suggest a pair of potentially habitable exoplanets possess stable tilts, which bolster the chances they are more Earth-like than we imagined.

Those planets are Kepler-186f and Kepler-62f, 550 and 990 light years from Earth, respectively. The former, whose discovery was first announced in 2014, was actually the first Earth-sized exoplanet found in the habitable zone of its star; the latter has a mass 2.8 times that of Earth (making a super-Earth). “It was already known that these two exoplanets are likely rocky, and they reside in the habitable region, where liquid water could exist on the surface of the planets,” says study author Gongjie Li, an assistant professor at Georgia Tech. “We are seeking to constrain the habitability of these planets further, to know better how likely these two planets could host life.”

Spin axis essentially determines how the heat and radiation emanating from a star gets distributed when it reaches that planet. Some axes will allow for this distribution to be relatively mild, while others might cause more extreme environments to arise. In addition, a planet’s tilt will sometimes oscillate back and forth, and larger oscillations on the axis could cause bigger variations in how this stellar radiation spreads, affecting the atmosphere circulation and the climate of the planet.

“It is not known in detail how the spin axis variations and the climate really influences the existence of life in general—robust life forms could exist in extreme environments, too—but a stable environment could be a good way to start,” says Li.

For instance, it’s thought that axial tilt is one reason Mars, despite being in the habitable zone of our solar system, lost a thick atmosphere and went from being a warm, watery world to a cold, dry hellscape within the last four billion years. The axial tilt of the red planet has varied wildly from zero to 60 degrees, and that instability means an inability to maintain a proper hold on its atmosphere. Earth’s axis, on the other hand, only oscillates between 22.1 and 24.5 degrees, roughly every 10,000 years, which is why the blue planet has been so good to life for so long. Li’s co-author, Yutong Shan from the Harvard-Smithsonian Center for Astrophysics, does point out that “Earth’s axial angle would also have been more unstable if it didn’t have such a large moon which, at least in this case, has a stabilizing effect.”

Kepler-62f and Kepler-186f were of particular interest because they exist farther from their host stars than Earth or Mars do. “Also importantly,” says Shan, “spin axis dynamics is richest in multi-planet systems because spin axis variability result from gravitational interactions between planets. Both 62f and 186f are in five-planet systems, and we understand the properties of the other planets pretty well because they all transit their star.”

After making calculations, the pair ran some simulations based on the numbers they had, and found that the spin axes for both planets are pretty stable, despite both lacking their own moons. In spite of having quite a few neighboring exoplanets to contend with in their respective star systems, they aren’t faced with gravitational effects that would destabilize their axes. “That’s good news to the kind of lifeforms whose emergence and survival rest on the long-term stability of their home planets,” says Shan.

Li believes this type of dynamical analysis of spin axis “can be easily applied to other exoplanetary systems,” and could go a long way in helping to bolster or reject suspicions of habitability for other worlds.

“I think the exciting to take away,” says Eric Agol, an astronomer at the University of Washington who first discovered Kepler-62f, “is that these type of dynamical studies can be connected to real systems. Now we actually have possible prospects to characterize [multi-]planetary systems like this. A lot of times that’s a problem doing theoretical work—with so many parameters to take into account, it isn’t always clear which targets have the most promise [for habitability] and which don’t.”

Lisa Kaltenegger, director of the Carl Sagan Institute at Cornell and part of the Kepler-62f (and 62e) discovery team, thinks the findings are part of a lively discussion on the role of axial tilt on exoplanet habitability, but she does emphasize, “life that develops on other worlds… should be able to develop for any axis tilt. Life would probably have evolved differently if Earth had had a different axis tilt, but no one knows if the differences would have been substantial or if we would just live in different parts of our own world.”

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Proxima b, our nearest neighboring exoplanet, is almost 25 trillion miles away. Even one of our fastest spaceships—the 31,600-​mile-​per-​hour New Horizons—would take hundreds of thousands of years to get there. Assuming we can’t figure out how to warp space-time (seems unlikely, but fingers crossed), we’re still looking at a couple-hundred-year trip in the best-case scenario, which leads to the real problem: No human crew could survive the entire ride. Science-fiction writers have long floated so-​called generation ships as a solution. Designers would outfit these interplanetary cruise vessels to support a ­community of adults and their children, and their children’s children, and their children’s children’s children…until humanity finally reaches a new celestial shore. Here’s our best guess for what it would take to sow the seeds of an extrasolar species. Career planning Successive generations need to fill all the vital crew roles—such as medics and mechanics—which doesn’t leave much room for freedom of choice. A version of modern career tests would assign occupations based on aptitude, passions, and available jobs. Propulsion We’re gonna need a mighty push. So far, no one’s had any better ideas than Freeman ­Dyson: Slap A-bombs on the back of a ship and physically shove ourselves forward with constant ­nuclear explosions. It’s not safe or healthy, but it’s all we’ve got.

Waste management

A healthy human needs almost 300 gallons of water a year, and there won’t be any pit stops. We’ll need to reclaim every drop we use. The ISS already packs a system to recycle astronaut pee, which we’ll scale up to avoid surges of raw sewage from the tap.

Petting zoo

Fluffy and Fido are too great a luxury for space, but evidence suggests a small menagerie of animals could help our immune systems. Toddlers who roll around in pastoral dirt may develop ­fewer allergies. Besides, furry friends do wonders for mental health.

People

One study estimated a starting crew of 160 could maintain a viable population for 200 years, provided they were a diverse bunch. Large gene pools provide crucial variety—we wouldn’t want any two passengers closer than sixth or seventh cousins.

Infirmary

A spaceship might have almost no bacteria, or at least a different set than the terrestrial microbes we’re used to. Our immune systems could weaken, or forget how to fight earthly pathogens. Visiting the homeworld might not be an option.

Dating

To avoid the pitfalls of inbreeding, a geneticist will regulate reproduction. Perhaps romance and parenthood would decouple; folks could pick their spouses but use in vitro fertilization for makin’ babies with optimal partners.

Shielding

Earth’s magnetic field protects us from DNA-frying waves. Deep space is more radioactive than low-earth orbit, so we’ll need stronger shields than our current ships have. A force field would be nice, but asteroid clay could also make a nice protective coating.

Arrival plan

We might not know much about Proxima b when we lift off. Our crew needs to be prepared, so we’d want a bit of everything: mining equipment to glean gases for terraforming, weapons to protect us from hostile life-forms, plus tools to build new homes.

Frozen people

The crew can manage in a closed system for a couple of centuries, but speculators say it’ll take 20,000 souls to start a healthy population on a new world. One space-­saving tip: Bring frozen embryos and people to diversify the gene pool upon arrival.

Farms

Two centuries’ worth of Spam sandwich fixin’s would weigh us down, so we’ll farm as we go. NASA is working on habitats to grow plants in space and are spec’ing out a system to turn poo into a fertilizer for cultivating protein-rich bacterial gruel (yum)

Self-propagating robots

What if Proxima b turns out to be a bust? We could hedge our bets by sending out self-­replicating robots to fan out through the galaxy in ever-­expanding networks. They’d spread on our behalf, eventually finding and preparing a home for us.

This article was originally published in the Summer 2018 Life/Death issue of Popular Science.

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Last year, the world got a look at an incredible star system, TRAPPIST-1, which had seven intriguing planets orbiting it. In those initial glances researchers figured out that—optimistically—five could potentially have temperatures that allowed for liquid water on their surfaces, with three of the seven planets located in orbits within the star’s habitable zone.

This was particularly exciting because where there’s water, there might be life. Here on Earth, life thrives when we just add water. But a closer inspection of those wet worlds, published this week in Nature Astronomy says they might be so bloated with water as to snuff out any potential for life. And even if some organisms did manage to develop, the study suggests, the massive quantities of water might keep us from detecting them.

But after years of looking for signs of water on other worlds, how could there possibly be a place where there’s too much water for life? Let’s take a look.

We’re talking really, REALLY wet

Earth seems like a pretty wet place. We drink our recommended eight cups of water a day, and our bodies are about 60 percent water by volume. Heck, water covers about 71 percent of this planet’s surface. That’s a pretty wet world, right?

Not compared to most of the planets at TRAPPIST-1. Though it might seem like Earth is awash in water, dihydrogen monoxide makes up just 0.02 percent of our planet’s mass. 0.02 percent. The rest of it is rocks and metals and organic matter and everything else on this world. In contrast, some of the planets around TRAPPIST-1 could have water that accounts for 15 percent of their mass. Or even more.

The data used by the authors of the Nature Astronomy paper suggest that in a few cases some of the world might be 50 percent water by mass, though later observations, published last month, put those estimates much lower, at around 10-15 or as low as 5 percent. Either way, that’s still tons of water. Two hundred fifty times the water in Earth’s oceans, in fact.

“We’re quibbling over lots and lots of water, or lots of water,” jokes Cayman Unterborn, a geoscientist and lead author of the paper.

Researchers can make those estimates even from 39 light years away by observing planets as they pass in front of their star. They can get a general idea of a planet’s size, but also its density, which tells us a lot about what it’s made of. These were about the size of Earth, but much, much lighter. Not so light that their weight could be attributed to some gaseous atmosphere, but not solid as a rock, either. That leaves water, and presents a world of new questions for planetary scientists.

No movement

A world with all that water would look really different from Earth, and even from the watery moons of Enceladus and Europa, which are vastly smaller than the planets of TRAPPIST-1.

On a truly water-rich planet, like the ones we’re talking about, there might be a thin outer layer of liquid water. But as you descended further into the planet, the pressure of the oceans above would grow greater, compressing the liquid water into solid, high-pressure forms of ice. That ice essentially acts as those planet’s mantle, surrounding some sort of core of even more solid material.

The dynamics of a world like that are alien to us.

On Earth, paleobiologists look to dynamic places on our fragile crust to find that first evidence of life, places where molten rock wells up to form hot spots at the bottom of cold oceans, or sends gasses from the deep interior out into the atmosphere. But on a world where the interior is solid, could life even develop?

“A really critical aspect of having an active planet is having it melt,” says Unterborn. “With enough water you’ll effectively shut off melting entirely, because the pressure is so high you’ll never get hot enough to do it. Yes, there is water on the surface—it is a habitable planet by the minimum definition—but you’re shutting off a lot of the geology. A lot of the communication between the surface and the interior is gone, and we think that’s necessary to be a habitable planet over geologic time scales.”

Not detectable

The low estimates for the planets in question are about 250 times as much water as is found in the Earth’s oceans, spread across planets the size of Earth. It would only take about a fifth of that amount to completely cover all of the land on our world.

Without dry land, the ability of water to weather stones down into their constituent parts is more limited. That means fewer raw materials produced by weathering, like phosphorous, the backbone of DNA. With that raw material limited, there’s less of a chance for life to develop in large enough numbers to produce a signal—like increased oxygen in the atmosphere—that would be detectable from Earth.

“In that case, you actually can’t tell the difference between the oxygen produced by life and the oxygen produced by planetary and geologic processes” Unterborn says, a situation that the researchers call habitable but not detectable. “Water worlds might be great places for life, but not enough to make an observable difference.”

That’s not all

With our current understanding of how life develops, it’s hard to imagine a scenario for its evolution on those super-watery worlds. And even if life had a shot, we probably wouldn’t be able to spot it.

But that doesn’t mean these planets are a dead end. Part of the reason the water worlds are so interesting to researchers is that accumulating lots of water (or lots and lots of water) is a complicated planetary process. The focus of this paper wasn’t really life, but how the planets got to be where they are. The high water content means they probably did not form in the positions that we see them today.

Planets start out as protoplanetary disks of gas and dust circling around host stars. Close to the star it’s hotter, so water stays vaporized. Water particles farther out become ice, which can slowly accumulate onto nascent planets. The line between these two is the ice line, (referred to in the paper as the ‘primordial snow line’ during the system’s early days), which shifts throughout a star’s lifetime as it dims.

In our solar system, planets close to the sun tend to be dry, while planets farther away are more water-rich. In the TRAPPIST-1 system, even planets closer to the sun have high concentrations of water. That means the planets probably had to migrate to their current positions over time, something that astrophysicists are still trying to explore.

Steven Desch, a co-author of the paper, says that one way this migration could occur is for planets to interact with gas within that protoplanetary disk. “The planets lose angular momentum making waves in the gas disk, and slow down and spiral in to the star,” Desch says. “That also provides a way to keep the orbits circular. Other mechanisms wouldn’t leave the system as orderly as we infer the Trappist-1 system to be.”

Their observations indicate that migration could have been substantial if the planets formed early on in the star’s 8 billion year history, or the planets could only have moved a small amount if they formed slowly over time, as the ice line moved closer to the star.

We still have a lot to learn about the development of other worlds, and looking at planets beyond our own small system can give us ever more interesting looks into the growth of the universe. But it’s going to take a lot of us to get the whole picture.

“I like to stress the interdisciplinary nature of exoplanets especially,” Unterborn says. “It’s not just astronomy—they’re really good at discovering them—but its the geology and chemistry that’s going to help contextualize everything. There’s a whole field that knows a lot about rocks. We should talk.”

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In December, Google and NASA researchers announced they’d found two new exoplanets using a neural network.

Now, the code used to make the discovery has been released for free.

“We hope this release will prove a useful starting point for developing similar models for other NASA missions, like K2 (Kepler’s second mission) and the upcoming Transiting Exoplanet Survey Satellite mission,” Chris Shallue, a Senior Software Engineer at Google, wrote on the company’s Research Blog.

Researchers can now use (and adapt) the computer code to look for new worlds hidden in the vast reams of data gathered by the Kepler space telescope.

The Kepler mission—and its successor, K2—hunt for exoplanets by looking for twinkles in the sky. When a planet passes between a star and a telescope, it creates a tell-tale temporary dimming. Between 2009 and 2013, when the Kepler mission ended, the telescope continuously watched about 150,000 stars, staring resolutely at a single patch of sky.

Researchers have confirmed the existence of 2,342 exoplanets using Kepler data, but there’s still a lot to go through. On the github page for the Google code, the researchers note that there are over three million files (one terrabyte) of Kepler data, which can take up to a week to download completely. It’s easier to look at the data in smaller chunks, which is how the Google team found the two exoplanets in the first place.

Automated software looks for those dips in light that might indicate a swiftly passing planet, which narrows down the data pool considerably. But astronomers still have to manually check that data to confirm the existence of a planet. Understandably, they focus on the most likely candidates, which leaves a lot of data unexamined. That’s where the neural network developed by Google comes in, taking another look at signals the automated software might have missed, and flagging likely candidates.

The Google program isn’t perfect. It can still mistake binary stars or other stellar phenomena for planets, and it is still being developed.

A similar approach has already been used for a while, but instead of using a machine brain, researchers turned to human brains all over the world, releasing Kepler data to projects like Exoplanet Explorers and Planet Hunters which let citizen scientists look through data and flag potential planets for astronomers to look at more closely.

Scientists just discovered a multi-planet system using the crowdsourcing approach in January.

Other data sets are increasingly becoming more accessible as the search for exoplanets continues. Earlier this year a group of universities released a large dataset of stars accumulated over 20 years by the ground-based W.M. Keck Observatory, which is also looking for exoplanets.

Whether you’re satisfied hearing about exoplanet discoveries after the fact, or you’d like to try your brain (or your computer’s) at discovering one for yourself, the search for exoplanets is only getting bigger. Things are likely to ramp up even more after next month’s launch of NASA’s Transiting Exoplanet Survey Satellite (TESS) which will look at 200,000 bright stars near our sun to see which might be similar to our own solar system.

What unknown worlds might be hiding near nearby stars? We’ll never know until we take a look.

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In his 1954 novel Lucky Starr and the Oceans of Venus, science fiction writer Isaac Asimov imagined seas filled with life and underwater cities on our neighboring planet. It wasn’t long, however, before we discovered what really lurks beneath Venus’s thick cloud cover. In the 1960s and 1970s, the United States’ and Soviet Union’s spacecraft found a dense, toxic atmosphere on Venus full of carbon dioxide and clouds of sulfuric acid. On the surface, temperatures were hot enough to melt lead, and the crushing pressure was akin to that found in Earth’s deep oceans.

All of this means that Venus is violently hostile to life. Even so, the planet is so similar to our own celestial body in size, makeup, and location that it’s often referred to as Earth’s twin. And in its distant past, it may have been even more Earthlike—scientists now believe that Venus could have once held oceans and a gentler climate.

“People don’t really fully appreciate how similar these two planets are,” says Suzanne Smrekar, a geophysicist at NASA’s Jet Propulsion Laboratory. “We hear so much about Mars, and yeah, currently its surface temperature is like Earth’s. But probably for most of its evolution Venus was much more like the Earth.”

Despite this similarity, it’s been nearly 30 years since the United States sent a mission to Venus. Smrekar and her fellow Venus researchers believe it’s high time we returned. Venus, they argue, can shed light on Earth’s history, what conditions a planet needs to become habitable, and whether the distant ones we are discovering beyond our solar system might have them.

“The quest to understand life in the universe involves not just the Earth, but the Earth’s twin,” says Stephen Kane, a planetary astrophysicist at the University of California at Riverside.

A world of difference

Billions of years ago, Venus and Earth formed relatively close together from similar materials.

Earth went on to become a wet, mild world ripe for hosting life. “You really need to have a way to create climate stability for life to get started,” says Michael Way, a physicist at NASA’s Goddard Institute for Space Studies. On Earth, plate tectonics, which cycles carbon in and out of the atmosphere, make that stable climate possible. When volcanoes erupt, they shoot carbon dioxide out from the planet’s interior. This greenhouse gas traps heat, keeping Earth toasty enough to support life. If carbon dioxide were allowed to build up, you’d get a hothouse like Venus. However, the Earth slowly recaptures carbon dioxide when it dissolves in rainwater, flows into the ocean, and is used to build carbonate rocks like limestone on the seafloor. As pieces of Earth’s outer shell shift and grind together, they carry carbon back into the mantle.

In other words, plate tectonics powers Earth’s thermostat. Our planet’s restless crust also recycles other nutrients, like phosphorus, that organisms need to survive. “The surface of the Earth is continually replenished by the plates moving underneath each other, Kane says. “Whereas Venus has essentially a single plate.”

While present-day Venus lacks plate tectonics, it may have behaved more like Earth in its early history. “Earth has been remarkably successful at keeping relatively clement climate conditions for at least the last 3.5 to 4 billion years,” Way says. Because the two planets are similar in so many ways, this suggests that Venus might have had a stable climate and oceans at some point as well, he says.

In fact, there is evidence of past water on Venus. Pioneer Venus, an American mission launched in 1978, measured a form of hydrogen called deuterium, also known as heavy hydrogen. On Earth, this isotope is much less common than regular hydrogen. But on Venus, deuterium isn’t quite so rare in comparison to ordinary hydrogen, indicating that a great quantity of the lighter version of the element has vanished. “If you measure a big difference in these numbers it tells you that something has escaped from the planet, basically, and that something is water,” Way says.

Another clue came when Venus Express—an orbiter launched in 2005 by the European Space Agency—measured twice as much hydrogen as oxygen escaping from the planet’s atmosphere. This suggests that the elements had once been joined as water.

It’s not clear how much water Venus actually had on its surface; it could have been anywhere from a few yards deep across the entire surface to hundreds of yards or more, Way says. To figure out what ancient Venus might have been like, he and his colleagues used a series of computer models to simulate the planet’s atmosphere. They reported that Venus could have had a shallow ocean and surface temperatures similar to those on present-day Earth for several billion years, up until around 715 million years ago.

Venus rotates more slowly than the Earth, which could have helped make it more habitable. Because the Venusian day is so long, the sun heats parts of its terrain for months at a time. At that point, “Warm air rises rather forcefully and creates a planetary-scale cloud that blocks much of the incoming sunlight,” Way says. “That can provide you a shield basically to help you be close to your parent star without overcooking in essence or boiling off your oceans.” This cloud would unleash heavy rains, although they would be concentrated around the area directly facing the sun.

At some point, though, Venus’s fate diverged from that of Earth’s, and the planet wound up as an “uninhabitable hellscape,” Way and his colleagues wrote last month in a paper published to the arXiv. It’s not clear why this happened, Way says. One possibility is that Venus’s seas began to evaporate because the planet receives more solar energy than Earth. In the upper atmosphere, sunlight would have broken the water vapor into oxygen and hydrogen, which then fled into space. Without water to weaken the crust so it could break up, there could be no plate tectonics as we know it. Venus would have become hotter and hotter as water vapor and carbon dioxide built up in its atmosphere.

“It has undergone this runaway greenhouse and now it’s stuck there,” Kane says. “All the carbon is in its atmosphere, it has nowhere to store it because it has no liquid water oceans.”

Earthlings, take heed

The scorching, poisonous place Venus has become can actually give us a glimpse into our own planet’s history.

When the Magellan mission orbited Venus in the 1990s, it took radar images of the planet’s surface that revealed mountains ranges. These features resemble mountains and plains of cooled lava created here on Earth when pieces of crust were jostled about by the sluggish churning of the mantle beneath them, scientists reported in December at the American Geophysical Union meeting in New Orleans. Similar forces might be active on Venus; it’s possible that the planet’s intense heat warms its crust enough that small pieces can slightly detach from the mantle about six to nine miles down. Some of the plains surrounding Venus’s mountains had been deformed, suggesting that blocks of crust could have been moving about pretty recently.

This isn’t full-fledged plate tectonics—but it might be the first step in the process. We have little record of how plate tectonics kicked off billions of years ago on Earth, so the more recent activity on Venus might offer a few clues, Smrekar says.

Our sister planet can help us understand present-day Earth as well, she says. Back in the 1970s, Venus proved key to our discovery that chlorofluorocarbons—chemicals used in hairspray, air conditioners, and other products—were a threat to the ozone layer. While creating computer models for the atmosphere of Venus, researchers at Harvard and MIT found that chlorine is really good at breaking apart oxygen compounds like ozone. Before long, another group at the University of California, Irvine, had realized that the extra chlorine we were pumping into our atmosphere might be doing the same thing on Earth.

Venus also offers a preview of our future. Over time, stars increase in luminosity. This means that the planets in their orbit will be bathed in more solar energy. For a planet with liquid water and an Earth-like atmosphere, that means a one-way ticket to Venusville. “Once you break a planetary atmosphere…[it’s] almost impossible to unbreak,” Kane says. “Venus could be the eventual outcome of all atmospheric evolution.”

In fact, it “seems inevitable” that Earth will eventually follow Venus’s path, he says. “The Earth has a delicate balance at the moment; it won’t last forever.”

Jekyll or Hyde?

We’re getting better and better at discovering planets beyond our own solar system—including ones about the size of Earth. We can’t study the soil or atmospheres on these planets to find out if they might be amenable to life, though. “The planets that we’re studying around other stars are planets that we will never be able to go to, at least not in the next several hundred years,” Kane says. “Venus is very much a warning to us, because if we did not have Venus in our solar system…we may very well be far more cavalier in discovering Earth-sized planets around other stars and just assuming that they’re habitable.”

Instead, we realize that two worlds that look the same from a distance can in fact be the Jekyll and Hyde of rocky planets. “As we discover new planets, the only basis we have for comparison are the planets in our own solar system,” says Lori Glaze, a planetary volcanologist at NASA Goddard. “Being able to differentiate between an exo-Venus and an exo-Earth is going to be really important in how we go forward in our exploration.”

It’s possible that Venus’s proximity to the sun is the main reason why it turned out so differently from Earth. But there could be other, more subtle forces at work too, like Venus’s lack of a strong magnetic field. “We’ll need to take those into account because it could mean that we have evil Venuses hiding amongst the planets we find around other stars,” says Kane. On the other hand, if Venus’s slow rotation rate once helped it sustain habitable conditions, it would make sense to measure how quickly exoplanets rotate as well.

“There’s this great cosmic accident that we have in our solar system: two planets that are so similar in size and adjacent in the solar system yet they are on opposite ends of the spectrum in terms of their habitability,” Smrekar says. “If you really want to understand what makes a planet habitable, really the big question is, why are Venus and Earth so different?”

Planning a visit

Even though Venus is our closest neighbor, there’s a lot we don’t know about it.

The planet’s thick blanket of clouds makes it difficult to observe, although missions like Magellan and Venus Express have taken radar and infrared images of the surface. Those pictures revealed another challenge: The surface of Venus isn’t very heavily cratered, indicating that it hasn’t existed for long enough to get dinged up much. “Over the last billion years and perhaps over a much shorter time even, the surface of Venus has been completely reworked,” Smrekar says. Perhaps because the planet lacks plate tectonics, heat periodically builds up underneath the crust until the surface is melted. Because of this, much of the evidence for what Venus’s surface was like in its ancient past has disappeared.

Then there’s the fact that Venus’s extreme conditions destroy any lander that visits within a matter of hours. “It’s a very tough place to send missions; it’s expensive and it’s risky,” Way says. “Mars is much easier to deal with.”

This means that funding is harder to secure for Venus than for the Red Planet. “Success begets success,” Smrekar says. “If you find an exciting discovery on Mars you want to follow up on that, and it’s been so long that we’ve had a mission to Venus that it’s hard to get over that hurdle.”

Still, Glaze says, “There’s getting to be quite a groundswell of support for Venus exploration.” Akatsuki, an orbiter launched by JAXA, Japan’s space agency, is currently gathering information about Venus’s climate. And last year, NASA scientists proposed two missions that would have sent probes directly into the planet’s atmosphere. The agency did not select either to advance in its New Frontiers program, but Smrekar, Glaze, and their colleagues are undeterred.

Smrekar would have led the Venus Origins Explorer (VOX) mission to investigate how present-day Venus behaves. It would have used an orbiter to map the planet’s surface and a probe to sample gases in its atmosphere. One of the questions Smrekar and her colleagues would have examined is whether Venus’s craters have been buried in lava flows, which would be a sign of recent geologic activity. They’d have also looked for chemical signatures of active volcanism, such as a thin coating of new minerals formed when lava flows are exposed to the atmosphere.

Another mission headed by Glaze—called Venus In situ Composition Investigations (VICI)—was awarded funding to hone its technology for future competitions. It would have sent two landers to visit highland plateaus that are older than the rest of Venus’s surface. These features might be similar to Earth’s continents, which are built from different kinds rock than its oceanic crust. VICI would have fired a laser into these rocks to vaporize a tiny bit of material, then measured the minerals present in both the plasma it had created and in un-vaporized rock. If Venus’s plateaus have a different composition than the rest of the surface, it could mean that water was involved in forming them.

During its sojourn, the spacecraft would also have measured gases like krypton and xenon. “Once they’re put into the atmosphere when a planet is forming it’s very hard to change them or remove them,” Glaze says. “They kind of remain there like little atmospheric fossils to tell us about what went into the original makeup of Venus’s atmosphere.”

She and her colleagues have built a full-scale prototype lander and tested its landing abilities here on Earth. The vessel is about 14 feet across and has a squat shape stabilizers that resemble spider legs to make it harder to tip over.

Glaze and her team are unfazed by Venus’s fearsome conditions. “We send things down to far deeper in the ocean [to] much, much greater pressures than we’re talking about on the surface of Venus,” she says. And most of the mission’s key measurements could be taken in under two hours—so by the time Venus’s scorching heat melts the lander’s electronics, they will likely have done their duty.

“Venus is hard to explore, sure, but it’s not like it hasn’t been done before 40 years ago,” Smrekar says. We haven’t sent a probe down into Venus’s poisonous skies since last century’s Venera, Vega, and Pioneer Venus missions. To know what to expect on the exoplanets are discovering far away, however, we’ll need to take another trip next door. “It’s incredibly important that we get back to Venus,” Glaze says.

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There’s a planet just over 4 light-years away orbiting a star at just the right distance—not too close, not too far—that it could support liquid water on its surface. We don’t know much about its atmosphere, if it even has one, and we’re trying to figure out more about its interior. There’s a lot more to uncover, but it sure sounds like it could be a promising place to find some alien neighbors, right?

If only we could figure out how to deal with the massive stellar flares.

A study published this week in The Astrophysical Journal Letters found that instead of a nice warm ring of dust around the star—which could indicate a cozy nursery of planets, as a study last fall reported—there was actually a huge stellar flare. (That’s the same as a solar flare, but on a star other than our own Sun).

It was the dust study that originally intrigued Meredith MacGregor, an astrophysicist at the Carnegie Institute who studies debris discs around other stars.

“Our solar system has discs, we have the asteroid belt and Kuiper belt, which we think are leftover material from when our planetary system formed. The ability to look at other stars and see the same structures is pretty exciting,” MacGregor says.

She’d looked at stars like Proxima Centauri before, and knew that they could be incredibly active—frequently firing off radiation-laden flares across many wavelengths of light, including the millimeter wavelength, which is often used to detect dust in other star systems.

“I was curious whether there was any possibility that the star had any major activity during these observations, and whether that had affected the results,” MacGregor says.

So she decided to dig into the data used in the previous study. The team had used 15 observations made over three months, totaling 10 hours of watching Proxima Centauri. For the most part, the star was quiet.

“In most of the observations the star wasn’t doing anything very exciting at all,” MacGregor says. “But for two minutes it had this massive brightening, and you can trace the evolution of the flux over time.”

That short period of brightening was a stellar flare. The previous study, MacGregor says, looked at the combined total of observations and interpreted the increased brightness as a potential planetary system, including a ring of star-warmed dust near the interior. That’s what the ALMA observatory looks for. It searches specifically for signals in the millimeter wavelength of electromagnetic radiation—similar to what comes out of your microwave.

“We’re probing different sized populations of grains by looking at different wavelengths,” MacGregor says. “The rule we use when observing systems is, the wavelength of the light that we’re looking at is the size of the grains that we’re seeing. So in the millimeter wavelength we’re tracing millimeter sized dust particles or ice particles.”

That’s important for understanding the underlying structure of stellar systems. But there are plenty of other things that show up in the millimeter wavelength, including stellar and solar flares.

“If you compare the absolute brightness of this flare to solar flares [in the millimeter wavelength], this flare we saw on Proxima Centauri is 10 times brighter than what we see on the Sun.” MacGregor says. But that doesn’t mean that this solar flare was 10 times larger than a flare from our Sun. This comparison is only for the millimeter wavelength, not all the other forms of radiation released by a flare event. Plus, the Sun and Proxima Centauri aren’t even in the same class of star.

“Proxima Centauri is an M dwarf, which is a much smaller star, and it has a much stronger magnetic field. We’re still learning a lot about how to compare the two different kinds of star,” MacGregor says.

Guillem Anglada, an astrophysicist and first author of the study that found dust in the Proxima Centauri system, agrees. “This is an important result that potentially will help to better understand the behavior of the atmospheres of M-dwarf stars. Proxima Centauri is the star closest to our Sun, and therefore an excellent laboratory to learn about the more distant ones,” Anglada says in an email.

Proxima Centauri captures our attention because it’s the closest star to our own, and it has a planet situated in just the right orbit to support liquid water. But Proxima b having an atmosphere—which is crucial to maintaining liquid water—becomes doubtful as solar flares increase.

“We caught this one flare in 10 hours of observing time on ALMA. Either it’s an incredibly lucky event, or chances are flares of this magnitude are happening pretty frequently on Proxima Centauri,” MacGregor says. “That would likely mean bad things in terms of the atmosphere of the planet, I would hazard to say.”

Large solar flares are typically accompanied by coronal mass ejections, or huge eruptions of heated, charged particles from the sun. If CMEs accompany flares on Centauri, the combo could not only bombard the planet with radiation, but also strip away any atmosphere.

“We don’t know yet whether flares on M dwarfs are also accompanied by coronal mass ejections. That’s kind of an open question,” MacGregor says.

Anglada says that he and his colleagues had also unexpectedly found the flare in a subsequent analysis of the data, independent of MacGregor’s work. “Our new estimates indicate that the amount of dust might be about one half our previous estimate, but we are still working in confirming this value. On the other hand, the paper by MacGregor et al suggests that the close environment of Proxima Centauri could be devoid of dust. The two studies have been carried out with a limited dataset obtained in an exploratory program. New observations with better sensitivity could provide resolved images that would definitely establish the architecture and main properties of the system.” Anglada says.

New observations will certainly be conducted, with plenty of interest in Proxima Centauri from both the public and the scientific community.

“A lot of questions need to be answered. This new result and the previous report with ALMA show that we know very little about our closest neighbors, and that we need to be especially careful and thorough in interpreting the data,” says Guillem Anglada Escude, an astrophysicist who helped discover Proxima b but who was not involved in the most recent study. (No relation to Guillem Anglada.)

Those questions include how frequent flares are, what their nature is, whether there might be other, cooler, debris discs further out in the Proxima system, what Proxima b is really like, and whether it has any planetary company. None of those answers will be easy to come by, but that makes hunting for them all the more exciting.

3/2/18 This post has been updated with comments from Guillem Anglada

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Earlier this month, New Scientist reported that NASA has plans in the works to visit Alpha Centauri. While the plan is reportedly “nebulous,” the space agency hopes to launch something by 2069. Here’s what we know:

First things first: Why 2069?

The proposed launch date may seem an odd (if rather giggle-worthy) choice. But NASA didn’t just pull this one out of their butts: While setting the agency’s budget back in 2016, Representative John Culberson of Texas called for NASA to send a mission to Alpha Centauri by 2069. He didn’t pull that date out of his butt, either; It’s an homage to the centennial anniversary of the Apollo 11 moon landing. Nice.

If you feel like you’ve been seeing the number 69 all over your space news as of late, you’re right! New Horizons—the probe that flew past Pluto and is currently delving into the outermost regions of our fair solar system—has a 2019 encounter planned with a mysterious object dubbed MU69. You can find out more about how it wound up with that moniker here. For some reason, NASA is currently on the prowl for a good nickname for the celestial body.

What’s Alpha Centauri and why would we go there?

What with all the far-flung exoplanets scientists keep discovering using various telescopes, it’s easy to forget that we’ve only physically explored a very tiny corner of our galaxy. Voyager 1 only recently made it past the boundaries of our solar system. We literally just saw the first documented extrasolar hunk of space rock come careening through our neighborhood.

The sad truth is that outside of our solar system, we don’t exactly have any close neighbors. The closest star system is Alpha Centauri, and it’s more than four light-years away. Alpha Centauri A and B are two stars twirling as a binary pair, but their third sibling—Proxima Centauri—is the closest. It’s actually pretty far from the other two (about 13,000-times the distance between Earth and the sun), so a “mission to Alpha Centauri” would probably just be a mission to Proxima Centauri.

Getting to the next solar system over is admittedly a pretty logical step in the whole space exploration thing. We got our feet all over the moon (and may do so again, if the President has anything to do with it), we’ve taken pretty pictures of all eight planets (and then some), and we’re planning probes to test the waters on potentially habitable ice moons. Shouldn’t we get some of our hardware out of the kiddie pool and into interstellar space?

Proxima Centauri carries the added benefit of at least one confirmed exoplanet, which may be rocky (read: vaguely Earth-like). It’s possible we could find life there, or at least learn something about how easy it is for life to evolve.

Will there be aliens?

Generally, if a planet has a rocky surface and liquid water, we consider it potentially habitable. We’ve only got one example of life to work with, and we know that water is pretty dang important to everything alive on Earth.

Because Proxima Centauri is a red dwarf star, its habitable zone—the range a planet can orbit in while maintaining liquid water—is much smaller than our own star’s. But it seems like at least one potentially rocky little planet is in that area. We still don’t know much about the planets and/or moons there, so it’s really too soon to say what we may or may not find. One would hope that we’ll know a little bit more by 2069. A private project called Project Blue intends to launch a space telescope capable of imaging the system by 2019.

How long would it take to get there?

That’s the tricky bit. Using our current technology, it would take a very, very long time. The New Horizons spacecraft travels at over 36,000 miles per hour, and that’s pretty much the bee’s knees in terms of speedy cosmic travel. But it would take a spacecraft like New Horizons around 78,000 years to reach Alpha Centauri. I’m all for planning ahead, but if we haven’t gotten people into interstellar space in 78,000 years, I’m quitting. Whether we invent warp drives or go extinct, such a spacecraft would surely become obsolete before reaching its destination.

NASA’s job is to find a faster way. That 2016 directive to shoot for the stars also specified that the agency should create a spacecraft for the job capable of traveling at 10 percent the speed of light. That would get us there in around 44 years.

Can we actually do that?

Maaaaaaaaaybe. There’s no reason to think it definitely can’t be done. The good folks at NASA aren’t even the only ones trying: A few years back, billionaire Yuri Milner launched an an initiative called Breakthrough Starshot to create a Centauri-bound probe. Starshot wants to create a light-propelled nanocraft—just a few grams of ship, shot into space with a giant laser pushing at its solar sails. In theory, this is possible. But we’ve got a long way to go.

NASA is supposed to work on this and other potential propulsion methods, none of which are anywhere near ready for primetime. In fact, none of them are above Technology Readiness Level (TRL) 1 or 2. That means we just know the basic principles that could make the propulsion systems work, or perhaps have some broad sketches of how we would harness those principles. A successful mission is TRL 9.

In other words, don’t hold your breath. But hey, 52 years is a long time. Maybe in 2113, humans will be eagerly awaiting confirmation of our first exoplanet probe’s arrival. Of course, it’ll take over four years for that signal to get back to us.

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A machine learning technique called a neural network has identified two new exoplanets in our galaxy, NASA scientists and a Google software engineer announced today, meaning that researchers now know about two new worlds thanks to the power of artificial intelligence.

Discovering new exoplanets—as planets outside our solar system are called—is a relatively common occurrence, and a key instrument that scientists use to identify them is the Kepler Space Telescope, which has already spotted a confirmed 2,525 exoplanets. But what’s novel about this announcement is that researchers used a AI system to spot these two new worlds, now dubbed Kepler-90i and Kepler-80g. The planet known as 90i is especially interesting to astronomers, as it brings the total number of known planets orbiting that star to eight, a tie with our own system. The average temperature on 90i is thought to be quite balmy: more than 800 degrees Fahrenheit.

Just as exoplanet discoveries are common, so too are neural networks, which is software that learns from data (as opposed to a program that have had rules programmed into it). Neural networks power language translation on Facebook, the FaceID system on the new iPhone X, and image recognition on Google Photos. A classic example of how a neural network learns is to consider pictures of cats and dogs—if you feed labeled images of cats into a neural network, later it should be able to identify new images that it thinks has cats in them because it has been trained to do so.

“Neural networks have been around for decades, but in recent years they have become tremendously successful in a wide variety of problems,” Christopher Shallue, a senior software engineer at Google AI, said during a NASA teleconference Thursday. “And now we’ve shown that neural networks can also identify planets in data collected by the Kepler Space Telescope.”

Astronomers need tools like telescopes to search for exoplanets, and artificial intelligence researchers need vast amounts of labeled data. In this case, Shallue trained the neural network using 15,000 labeled signals they already had from Kepler. Those signals, called light curves, are measures of how a star’s light dips when a planet orbiting it passes between the star and Kepler’s eye, a technique called the transit method. Of the 15,000 signals, about 3,500 were light curves from a passing planet, and the rest were false positives—light curves made by something like a star spot, but not an orbiting planet. That was so the neural network could learn the difference between light curves made by passing planets and signals from other phenomena.

Eventually, Shallue and his collaborator, Andrew Vanderburg, a NASA Sagan postdoctoral fellow at the University of Texas, Austin, turned the neural network loose on data from Kepler that wasn’t in its original training set. It sifted through data from 670 star systems, focusing on weak signals that could possibly represent a previously undiscovered planet. And sure enough, they found two new worlds.

“Machine learning really shines in situations where there is too much data for humans to examine for themselves,” Shallue said.

Looking through the weak signals from those 670 stars and finding two planets was “proof of concept” that their neural network works, he says. Their next step is to use it on much more data: signals from about 150,000 additional stars. And Shallue concedes that he’s no an astronomy expert, which is why he collaborated on the project with Vanderburg.

While artificial intelligence tools have been used in this kind of research before, “this is the first time a neural network specifically has been used to identify a new expoplanet,” Shallue said during the press conference.

Mary Beth Griggs contributed research to this report.

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We have discovered a planet. It gathers in light from its sun, and refuses to let go. In return, the star strips away the planet’s atmosphere, slowly devouring it.

That’s how the popular planet-inventing Twitter bot Newfound Planets , might describe this particular gaseous giant, smashing together verbs and adjectives into a delicious galactic treat that has to be too good to be true.

But this is entirely real. WASP-12b is a burning monster of a world, a ‘Hot Jupiter’ orbiting a star 1400 light-years away. Scientists first discovered the planet back in 2008, but recent observations made with the Hubble Space Telescope show that the planet is very unusual (even amid its fellow extrasolar worlds with glowing atmospheres, scorching temperatures, or ruby-adorned clouds.

In a study published last week in The Astrophysical Journal, researchers found that WASP-12b is far darker than previous glances through ground-based telescopes had implied. This is the first time scientists have been able to quantify its darkness.

Usually, planets of that size and type reflect back about forty percent of the light they receive from the star they orbit. But this planet absorbs about 94 percent of that glare.

What’s even more unique is the distance that light has to travel. WASP-12b is massive, but it orbits at a range of just 2 million miles from its sun. By comparison, Earth, which is much smaller, orbits our Sun at a gap of almost 93 million miles. This relatively short travel time means that the planet completes an orbit of the sun in about 24 hours. In other words, it’s year is our day. The planet is also tidally locked to it’s star, with one side constantly illuminated, and one trapped in an endless night.

The proximity also means that the planet’s day side gets extremely hot—over 4,600 degrees Fahrenheit. That’s so hot that bright, reflective clouds can’t form in the sky, leaving almost nothing to reflect light away from the planet’s surface. Some clouds can form in the much cooler evening side, but since they face away from the sun, they aren’t sending back much light either.

The lack of reflectivity means that the planet converts all its light to heat, maintaining a steady, searing hot temperature. It also makes the planet appears pitch-black to observers. But the star isn’t letting the planet steal its light without a fight. Instead, it’s siphoning off bits of the planet’s atmosphere and pulling the gasses into itself.

While this is an extremely hot find, it’s not the first dark planet that scientists have discovered, or even the darkest. Back in 2011, researchers discovered that another hot gas giant—TrEs 2b—had a surface blacker than coal or acrylic paint absorbing almost all light that reached it. But, unlike WASP-12b, we’re still not exactly sure what makes this particular planet so inky. Future research will have to enlighten this dark mystery.

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Picture Jupiter, the gas giant. Now inflate it to over five times its size. Throw in a sun close enough that it can heat the planet’s atmospheric surface to 4,600 degrees Fahrenheit.

Meet WASP-121b, known as a “hot Jupiter.” It is an exoplanet—a planet outside our solar system—900 light-years away from Earth that shares a surprising feature with our home planet: a stratosphere.

In a study published this week in Nature, researchers used the Hubble Space Telescope to visualize WASP-121b’s stratosphere, an outer atmospheric layer that has never been convincingly shown in planets outside our solar system before. To give you some context of where its located, there’s a good chance you’ve visited the stratosphere: when you’re flying in a plane, that is. On Earth, the stratosphere is located above the troposphere (where we live) and below the outermost layers of our atmosphere. The defining characteristic of the stratosphere is that the temperature gets warmer as you move outward.

“There were theoretical reasons to expect this would be happening in exoplanets’ atmospheres,” says Thomas Evans, first author of the study and a research fellow at the University of Exeter. “But these exoplanets are distant, far away, exotic objects. It’s always difficult to predict what their atmospheres will really be like.”

To understand how WASP-121b’s atmosphere behaves, the scientists looked at the infrared light emitted by water molecules in the exoplanet’s atmosphere. This release of radiation can happen when the water molecules are repeatedly absorbing and releasing a lot of energy—if they are, for example, in very hot surroundings. Humans can’t see infrared light because our eyes can only detect a narrow range of light waves. But that’s not a problem for the Hubble Space Telescope.

And what Hubble captured was remarkable: The water molecules were glowing. Like a burning candle or the pulsing of hot coals, the glowing upper atmosphere meant that there was a lot of energy or heat being released instead of absorbed. This indicates that WASP-121b has a stratosphere that gets warmer further from the planet’s surface. Based on those emissions, the temperature increases by 1,000 degrees Fahrenheit across the span of the stratosphere.

But if you think about it, that doesn’t entirely make sense because, at almost -500 degrees Fahrenheit, space is very, very cold; you’d expect that as you shoot out toward that frigid expanse, you would get colder. On Earth, our stratosphere has an inverted temperature gradient because of ozone within the atmospheric layer. The ozone heats up the outer stratosphere by absorbing the Sun’s UV radiation. But that’s Earth, not a distant “hot Jupiter.” So why does WASP-121b have a stratosphere like our much smaller, rockier planet?

That’s a question that the researchers are still trying to answer. They think compounds in WASP-121b’s atmosphere—titanium oxide and vanadium oxide—could be keeping its outer layers toasty, but it will take more studies to figure that out.

Although understanding exoplanet atmospheres won’t necessarily help us understand our own solar system, the researchers are thinking bigger than that. The technology isn’t quite there yet, but Evans hopes that scientists will one day be able to study the atmospheres of smaller exoplanets to figure out if they could support life. Focusing on planets in our own solar system limits the scope of what we can learn, Evans says.

“There is a vast spectrum of planet atmospheres,” Evans says. “In order to develop a more complete understanding, we need to explore this vast population of exoplanets.”

And it’s the perfect time for this research, with the newest Hubble-spin-off ready for launch next year: We’re ready for you, James Webb Space Telescope.

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Sure, watching ice freeze sounds about as fun as watching paint dry. But that’s just because you haven’t tried making ice with some of the most powerful lasers in the world.

By firing the most powerful x-ray laser in the world (the Linac Coherent Light Source) at a vial of water, and taking the equivalent of high-speed camera images with pulses from another powerful laser, researchers were able to view the water lining up molecule by molecule into a phase of ice known as ice VII—a form normally not found on Earth.

Their results were published this week in Physical Review Letters.

“There have been a tremendous number of studies on ice because everyone wants to understand its behavior,” study author Wendy Mao, said in a statement. “What our new study demonstrates, and which hasn’t been done before, is the ability to see the ice structure form in real time.”

In this case, real time means just six nanoseconds. That’s a fast freeze.

Other scientists created Ice VII in the lab before, but hadn’t successfully captured the freezing process. It turns out that this phase of ice—more commonly associated with planetary collisions in space—starts forming as tiny rod-like needles before freezing solid. Previous research indicated that the ice might first freeze into spheres instead. The new findings give us insight into all the weird ways that water can freeze, and are particularly exciting because while ice VII doesn’t exist on Earth in nature, planetary geologists do think that it exists on Europa and other exoplanets.

Ice on Earth, from the rocks in your whisky to the Greenland ice sheet, all freezes into the same phase: your typical, run-of the mill ice Ih (pronounced one h). The ‘h’ refers to the hexagonal shape that oxygen atoms line up in when transforming from a liquid or gas into solid ice.

But the hexagon is far from the only shape that water molecules can congregate in. All told, there are about 17 different crystalline phases that water can assume, given the right temperatures and pressures. (An 18th might exist in a weird, square form.) Earthly temperatures and pressures don’t vary by that much, compared to the vast and incomprehensible universe as a whole, so ice Ih is the only thing that shows up on our world.

But in other places and situations, where temperatures are higher and pressures lower than Earth (or vice versa), liquid water, water vapor, and ice might be stable at completely different points. Scientists conceptualize this using a phase diagram, which literally maps out the conditions under which a substance would be liquid, gaseous, or solid.

There are a number of distinct ways that the molecular components of water can line up into a solid, which is why the compound’s phase diagram is so strange.

Ice, ice, baby

Ok, fine, Vanilla Ice is not actually on the phase diagram. Water’s real phase diagram looks more like this—with roman numerals thrown all over the place.

Ice Ih dominates the space below 1 kilobar of pressure (almost 1,000 times the atmospheric pressure at sea level) and between freezing and -328 Fahrenheit. But move out of those frigid boundaries, and things start to get weird. Ice can exist at ridiculously high temperatures (think hundreds of degrees celsius) when it’s sufficiently under pressure.

Of the 17 recognized forms of ice, 11 show up on a typical phase diagram. IV, IX, XII, XIV, XVI, and XVII are weird cases. (For Vonnegut fans, no, ice IX will not freeze all water on Earth.) The first four are all metastable in other phases, meaning that they can exist briefly in the domains of other ice structures—so long as they are undisturbed. But change their temperature and pressure, and you can make them shift into another, more stable phase. Ice XVI and XVII were experimentally formed by stretching out ice in really low-pressure environments, leaving tiny molecular cages in between the frozen water molecules.

You’re not likely to ever encounter these forms of ice in your life. But isn’t it cool to know they’re out there?

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After Pluto got demoted in 2006, we were back to being a boring old eight-planet solar system. Then, last year, astronomers announced they’d found hints of a hidden ninth planet in the outer solar system. Scientists are still trying to figure out whether Planet Nine really exists, and now it seems they’re already speculating about a TENTH planet, also dark and mysterious–and possibly not actually there. What a whirlwind.

In a paper in the Astronomical Journal, planetary scientists Kat Volk and Renu Malhotra from the University of Arizona suggest there may be another planet hidden on the outskirts of the Kuiper belt. If it’s there, they think it could be similar in mass to Mars and Earth, orbiting the sun at a distance of about 60 AU. That’s 60 times the distance between the sun and Earth.

Planet Nine, by contrast, may be 10 times the mass of Earth, circling the sun from as far as 700 AU.

Out beyond Neptune, the Kuiper belt is a huge, crowded ring of icy junk leftover from the formation of the solar system, like comets and dwarf planets such as Pluto. And in fact, if the hypothetical Planet Ten is as small as the scientists think it is, it may not have enough gravity to clear its orbit of debris, which is one of the requirements necessary to be considered a planet. That was the same problem that got Pluto in trouble 11 years ago. If it hasn’t cleared its path around the sun, Planet Ten could be just another dwarf planet, a second-class planetary citizen who doesn’t get a ton of respect.

For now, Volk and Malhotra have only seen the gravitational footprints of a possible hidden planet–nobody’s laid eyes on the real thing. They think it’s there because something’s tilting the orbits of distant Kuiper Belt Objects (KBOs) out of whack.

KBOs orbit in a mostly flat disk around the sun. Some orbits are tilted a few angles this way or that, like the rim of a jaunty hat, but overall the orbits average out into a flat plane. That’s for most of the Kuiper belt. Studying more than 600 KBOs, Volk and Malhotra found that the most distant objects in the belt average out to a plane that’s tilted by eight degrees. So something is warping the orbital plane of the outer solar system.

“The most likely explanation for our results is that there is some unseen mass,” Volk said in a statement. “According to our calculations, something as massive as Mars would be needed to cause the warp that we measured.”

But there’s also a chance that the warp could be caused by more than one object, the authors note, or that a passing star could have skimmed by and caused gravitational disturbances in the outskirts of the Kuiper belt.

How could scientists have overlooked a Mars-sized planet in our own solar backyard all this time? Well, the solar system is a big place, and we haven’t fully mapped it out yet. And if the planet is lined up with the plane of the galaxy, the multitude of stars could make it hard to pick out.

It will likely take years of research to determine whether Planets Nine and Ten are really out there. The Outer Solar System Origins Survey is currently searching for and tracking thousands of distant objects, and Malhotra is optimistic that the Large Synoptic Survey Telescope (LSST), slated to come online in Chile in 2020, will help to narrow the search.

“We expect LSST to bring the number of observed KBOs from currently about 2000 to 40,000,” Malhotra said. “There are a lot more KBOs out there — we just have not seen them yet. Some of them are too far and dim even for LSST to spot, but because the telescope will cover the sky much more comprehensively than current surveys, it should be able to detect this object, if it’s out there.”

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It might seem like NASA is constantly announcing a brand-spanking-new “Earth-like” exoplanet—some far-away world that might possibly maybe have the basic requirements for life as we know it. And it seems that way because, well, that’s pretty accurate: it’s all thanks to NASA’s wildly successful Kepler Space Telescope, which uses the blinking and dimming of distant alien stars to spot planets that might orbit around them. But the latest Kepler finds (219 new planetary candidates, 10 of which are Earth-size and the right distance from their host star to hold liquid water) mark something of an end: this represents the final official planetary search results from Kepler’s mission data.

This requires a little bit of unpacking. After all, as you may know, the Kepler Space Telescope is still out there in space finding new planets—and will probably continue doing so for about another year. But the telescope’s primary mission ended prematurely when the darn thing broke in 2013: the telescope has four wheels meant to keep it pointed at one patch of sky so it can stare down any subtle star flickers indicating the presence of a plant. Then two of the wheels broke. Instead of giving up on the craft entirely, NASA engineers figured out how to use the sun as a virtual reaction wheel; the physical force of light pressing against Kepler’s solar panels keeps it in place as the other wheels push back. So Kepler had a second chance, with a new mission dubbed “K2”.

K2 has already found several exoplanets in its own right, but the mission is a little different. In its first mission, Kepler stared at one patch of sky, looking for signs of planetary activity around 150,000 stars in our cosmic backyard. K2 is subject to the sun’s position; it can’t just point anywhere scientists want to point it. And once they pick a target that works—one with stars worth looking at, but that’s in the right spot for the sun to give an assist—the team only has about 80 days before the telescope has to move again. K2 has spotted (and will continue to spot) new planets, but it doesn’t produce the glut of data that the original mission provided.

And that brings us back to NASA’s latest news: four years after Kepler’s hardware failure, the massive catalog of data it produced has finally been combed through to NASA’s satisfaction in its entirety.

“All the data from the original Kepler mission has been analyzed, much of it several times,” Kepler and K2 mission manager Charlie Sobeck told PopSci in an email. “This latest catalog is a reanalysis using improved software that has been well characterized, which makes the catalog particularly good for drawing statistical conclusions. This represents the final planet search results that the mission will deliver.”

The new data analysis brings the total number of planetary candidates (possible planets that haven’t necessarily been confirmed) to 4,034. Just over half of those have been verified using other telescopes. Of the 50 planets thought to be Earth-size and in their star’s habitable zone (10 of which were announced in the new batch) just 30 are confirmed.

The new findings also revealed something about the planetary family tree: in measuring the precise size of some of the Kepler planets, scientists determined that “small” planets (ones smaller than gas giants like Jupiter) fall into two clean-cut categories. They’re either relatively close to Earth-size (some so-called super-Earths) are several times more massive than our own planet, but that’s pretty close in the cosmic scheme of things) or they’re all the way over on the relatively-Neptune-like end of the spectrum, forming “gas dwarfs” or “mini-Neptunes”. The findings suggest that it’s relatively common for new planets to be close to Earth-size, but that some of them get a dose of gas that sends them sprinting into the heavier weight class.

“We like to think of this study as classifying planets in the same way that biologists identify new species of animals,” Benjamin Fulton, a doctoral candidate at the University of Hawaii in Mano, said in a statement. “Finding two distinct groups of exoplanets is like discovering mammals and lizards make up distinct branches of a family tree.”

Figuring out where Earth and its close cousins sit on the planetary spectrum can help us determine how planets tend to evolve—and by extension, how commonplace it is for them to evolve with all the components that make life possible on Earth. Kepler has done some amazing work in pushing planetary science forward. And even though it’s technically done with part one of its mission, chances are that scientists will continue to identify the odd planet now and then from its massive data set.

“I expect that the scientific community will continue to scour the data set for decades, finding new planets and new features of the stars themselves,” Sobeck said. “So you can expect to see future exoplanet announcements based on the data, but probably not from the mission itself.”

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About 650 light years away, a planet hotter than many stars is hurtling around its sun, leaving a glowing trail of gas in its wake like some sort of superheated comet.

In a paper published Monday in Nature, researchers announced the discovery of the gas giant orbiting an incredibly hot star, KELT-9, which is twice as large and twice as hot as our sun.

The Jupiter-like planet orbits KELT-9 over the star’s poles—as opposed to around the star’s equator—at a rapid clip. It transits once every 36 hours, passing between its host star and Earth’s observing telescopes. The planet, known as KELT-9b, is tidally locked, with one side constantly enduring the intense radiation of its sun and the other side plunged into perpetual night.

On the day side of the planet (which is almost three times the size of Jupiter, but only half the mass) temperatures reach 7,800 degrees Fahrenheit. That’s only about 2,000 degrees cooler than our own Sun, and it’s the same temperature of stars called brown dwarfs.

But despite its size—and the heat of its surface—the researcher say it’s definitely not star material.

“The inside of the center of the planet is nowhere near hot enough to fuse hydrogen and helium,” says study author Scott Gaudi.

Gaudi and his colleagues kept track of the planet with the help of observations from volunteer amateur astronomers, watching as the planet crossed in front of its star and disappeared behind it. One of the major telescopes used in this endeavor was the Kilodegree Extremely Little Telescope (KELT), which helps astronomers look for planets around very hot stars, like KELT-9. The researchers used those measurements and observations to start getting a clearer picture of what this strange planet is like.

For one thing, the extreme radiation and heat from the star are probably pushing material out of the planet, forming a glowing trail of gas behind it. And molecules like water or methane couldn’t form in the intense heat of the day side of the planet.

Most other things about the planet remain unknown, but researchers do think that the planet’s strange orbit points to a violent past.

“This planet has a very long and tortured history,” Gaudi says. He explains that planetary scientists think that many planets form in protoplanetary discs—vast discs of gas and dust orbiting roughly around a host star’s equator. The planets forming in the disc tend to stay in that same plane, but might get knocked into a different orbit (like the strange perpendicular orbit of KELT-9B) if another object slammed into it like a billiard ball.

And things aren’t likely to get much better in the planet’s future. Eventually, the intense radiation from the sun might evaporate the planet entirely, or reduce it to a rocky barren world like Mercury, depending on the planet’s composition. If not, then it will get obliterated when KELT-9 blows up into a red giant later in its life cycle.

But that’s a very long way off in the future. The researchers still hope to get time on other observing platforms, like the forthcoming James Webb Space Telescope, to help them gather more data about what the atmosphere on the planet might be like in the present. They also hope to learn how well heat is transferred from the day side of the planet to its cooler night side. Strong winds might help redistribute the heat around the planet, but more observations are needed.

There’s still plenty of time to make observations, but this particular planet won’t be visible from Earth forever.

“We were pretty lucky to catch the planet while its orbit transits the face of the star,” co-author Karen Collins said in a statement. “Because of its extremely short period, near-polar orbit and the fact that its host star is oblate, rather than spherical, we calculate that orbital precession will carry the planet out of view in about 150 years, and it won’t reappear for roughly three and a half millennia.”

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There’s a big eclipse coming up. No, not the total solar eclipse in August that we’re all really excited about. This one will happen in September around a star 1,000 light years away. Sure, it will be much more difficult to observe than our Moon passing in front of the Sun, but it could give us clues about a distant solar system.

In a paper released on arXiv and set to be published in the Monthly Notices of the Royal Astronomical Society, astrophysicists announced that they think they’ve found a massive planet 50 times larger than Jupiter with a vast ringed disc—think Saturn, but bigger—surrounding the entire planet.

It’s located 1,000 light years away in the Orion system, orbiting a young, bright star that is slightly larger, but the same temperature as our Sun. Over the past 15 years, various telescopes observed the star. In 2008 and 2011 researchers noticed odd eclipses—or transits—every two and a half years, during which the light from the star dimmed for between two and three weeks.

Watching for a star to dim, and measuring the resulting dip in brightness as a planet passes between the star and an observing telescope, is one of the principle ways that researchers can glean information about exoplanets.

“What’s exciting is that during both eclipses we see the light from the star change rapidly, and that suggests that there are rings in the eclipsing object, but these rings are many times larger than the rings around Saturn,” astronomer Matthew Kenworthy said in a statement.

This isn’t the first ringed object that’s been found outside our solar system, but it might be the first with a regular, predictable orbital period.

But it’s important to note that this giant planet with rings hasn’t been officially found yet. Telescopes all over the world will be pointing at star PDS 110 this September 9-30 when the ringed object is expected to make an appearance again. Ground-based telescopes will have just a few hours each night to observe the star (space-based telescopes might have a more uninterrupted view). The researchers hope that the observations this fall will show that the dimming of the star is due to the crossing of a giant exoplanet and a ringed disc of dust and rock where moons are just starting to form.

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Ocean baking

All those green waves swirling around are what ocean scientists call glacial flour, though it’s not the kind you bake with. This “flour” is the result of iron-rich rock sediment that’s been ground down into super fine particles by glaciers. These particles turn the water around them into a beautiful sea of green. The color change also stimulates the growth of viridescent phytoplankton, further mixing this flour into the sea. The mix usually arrives with spring, but it may have come a little early this year, according to some reports.

Shape shifters

The Ebbinghaus illusion, pictured above, has tricked the minds of many people who’ve eyed it. Most viewers see the red dot on the left as smaller than the one on the right. But if you measured them, you’d find they are exactly the same size. That’s because of the way the dots are arranged. Your brain sees the left red dot as closer, given the giant dots around it, and the right red dot as farther away, given the tiny black dots around it. When the brain sees them both at once, the only way for the right red dot to be farther away than the left red dot, is if it’s larger. Still confused? Here’s a more in-depth description.

Times they are a changin’

To keep up with and understand our rapidly changing planet, NASA researchers have sent satellites into orbit to take pictures and track the progress. But there’s been a lapse for quite some time, so NASA put Operation Icebridge into action: A series of flights and across our planet’s poles. The project’s missions over the Arctic just wrapped up and revealed some stunning images of like this one above, displaying meltwater in crevasses in southern Greenland. You can see the rest of the gorgeous and informative snapshots here.

Earth’s cousin, many light years removed

Above is an artist’s depiction of Proxima b, an Earth-like exoplanet a mere 4.2 light years away. Despite the distance, Proxima b might look a lot like us: It orbits its star in what’s called the habitable zone, an area that scientists think could allow planets to harbor life as we know it. To better understand that chance, scientists used mathematical models, typically employed to simulate climate change on Earth, to estimate what Proxima b’s atmosphere might be like under different conditions. Their results suggest that if Proxima b does indeed have an Earth-like atmosphere, it could be habitable.

One ovary to go, please

We are one step closer to being able to treat fertility issues with 3D-printed, lab-grown ovaries. In a paper out this week in the journal, Nature Communications, researchers at Northwestern University published their recent success: They grew follicle cells, taken from a mouse, inside a 3D printed vascular scaffold and then transplanted that scaffold into an infertile mouse, allowing the start of a normal hormonal cycle and the birth of healthy pups. The researchers hope this treatment could be used in humans in the future. A piece of the 3D printed scaffold is shown above.

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A second Earth may orbit our nearest neighboring star, and according to new simulations, it may be comfortable for life as we know it. Maybe.

Proxima b is thought to be rocky and roughly Earth-sized, and it orbits its star in the habitable zone, where it’s theoretically not too hot and not too cold for water to form lakes and streams on its surface. Plus, it’s only about 25 trillion miles away—how convenient!

It sounds great, right? But there’s still a few things we need to know about Proxima b. We don’t know if it has an atmosphere or water, and as a result we also don’t know what the temperatures are like there. We don’t know if it has a magnetic field to protect its atmosphere from stellar flares, or if it burned to a crisp ages ago.

To see how a few different scenarios might play out, scientists at the University of Exeter plugged Proxima b data into the Met Office Unified Model, which is usually used to model climate change here on Earth.

They found that if Proxima b has an atmosphere similar to Earth’s, or even a simpler atmosphere made of just nitrogen and carbon dioxide, then it stands a pretty good chance of maintaining a comfortable temperature to support liquid water—and by extension, maybe life.

Those results held true even when scientists threw a few theoretical wrenches into the simulation. Proxima b orbits very close to its star, which means that one side of it may permanently face the light source while the other remains dark and cold. Even in this scenario, the “hot” side maxed out at a comfortable 62 degrees Fahrenheit. (The cold side was about -190 degrees, so maybe that’s not a great place to build our future colonies…)

Similarly, they found that if Proxima b has an orbital eccentricity like Mercury—that is, if it spins three times on its axis for every two times it revolves around the sun—parts of it it might still support water (if it has an Earth-like atmosphere).

These results generally line up with what other climate models have suggested, but we still have no idea what’s really going on on this planet. We may just have to send tiny spaceships to find out.

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On the one hand, it’s hard to get excited about every single Earth-ish exoplanet that astronomers discover when it seems like we’ve got a new one (or seven) on the books every month or so. On the other hand, uh, we’re basically discovering new Earth-ish exoplanets every month or so.

April’s “is it aliens?” entry is LHS 1140b, a “super-Earth” described Wednesday in the journal Nature. The basic stats are these: it’s just 39 light-years away in the constellation Cetus (The Sea Monster, rawr), it’s just under one-and-a-half times the size of Earth (though it’s a lot denser, with over six times our mass), and it orbits a faint red dwarf star.

“This is the most exciting exoplanet I’ve seen in the past decade,” lead author Jason Dittmann of the Harvard-Smithsonian Center for Astrophysics said in a statement. “We could hardly hope for a better target to perform one of the biggest quests in science—searching for evidence of life beyond Earth.”

Little red dwarfs have become a big focal point for astronomers hunting for habitable planets. For a long time, planet-hunters focused on bigger stars similar to our own sun. After all, we only know of one place where life successfully evolved—so it makes sense to try to find solar systems as close to our own as possible. That’s why “Earth-like” exoplanets get so much buzz, too: these are worlds that researchers estimate to be rocky, based on their mass and their distance from their host star (as opposed to massive planets made of gas), so they have surfaces not totally unlike the own found on our own planet. In theory, rocky worlds that sit in their star’s “habitable zone”—not so close as to turn into a sizzling rocky like Mercury, but not so distant as to freeze over like Pluto—could maintain liquid water, given the proper atmosphere. And we know water is a key ingredient for life, at least as we know it.

But in recent years, red dwarfs have gotten more attention. The “dim bulbs” of the Universe are more plentiful in our neck of the woods than sun-like stars, and they’re also older—which means any rocky planets they host have had plenty of time to evolve a microbe or two. Most rocky planets around red dwarfs are thought to be tidally locked (one side of the planet always faces the sun, while the other sits in perpetual darkness) but hey, beggars can’t be choosers.

LHS 1140b is thought to be at least five billion years old (about 500,000,000 years older than Earth), and it’s right smack dab in the middle of its stars habitable zone: it’s 10 times closer to its star than the Earth is to the sun, but because of the star’s diminutive nature it only receives about half as much light. Young red dwarf stars emit violent shots of radiation, which can bake their closely-held planets beyond any hope of habitability. But because of LHS 1140b’s size and density, researchers believe it would have cooled down slowly enough after its formation to maintain a large ocean of magma for millions of years. The constant output of steam from this roiling lava may have been enough to keep the planet’s atmosphere moist during its star’s wild youth.

Dittmann and his colleagues think the newly-discovered exoplanet is the perfect target for the soon-to-launch James Webb Space Telescope. Scientists will be able to examine light as it passes through LHS 1140b’s atmosphere (assuming it indeed has one), which will allow them to analyze its chemical composition. The team has already secured time on the telescope, though they’ll continue to observe the planet using data from the Hubble and other already functioning scopes in the meantime.

We’ll have to wait a while before we know if LHS 1140b has any atmosphere to speak of, let alone one full of the life-giving molecules that astrobiologists covet. And even if all the ingredients are there—even if all of the proverbial lights are on—it’s quite possible that no one is home. And while 39 light-years is basically our backyard on a cosmological scale, there’s no way a probe will ever visit this alien world in our lifetime. Luckily, some of the best habitable world candidates are actually moons within our own solar system. Exoplanets like LHS 1140b can reveal invaluable secrets about how planets form and how often they come with a habitability starter pack, but you can be pretty sure that we’ll track down our first alien lifeforms a lot closer to home.

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Have you heard the good news? On Wednesday, scientists announced a fleet of new planets. And not just any old exoplanets: they unveiled a solar system seemingly jam-packed with Earth-sized worlds. Those seven probably-rocky bodies could be an excellent place to search for life. And the good folks at NASA have created a whole new website devoted to the TRAPPIST-1 system. There’s a lot to unpack here.

First things first: Remember those illustrations that always got sent out with new exoplanet discoveries? The artistic interpretations based on whatever scant data we might have on the planet? Forget ’em. NASA has created a 360-degree video that puts you right smack dab on the surface of one of the newly discovered worlds. Never mind the fact that all we really know, with reasonable certainty, is that the planet in question is about the same size as Earth, and is rocky—like Earth, Mars, Mercury, and Venus—and orbits around a red dwarf star. For all we know, TRAPPIST-1d could have black sand beaches surrounded by purple oceans full of evil, hyper-intelligent jellyfish. But, like, okay, this is a reasonable guess:

If that’s not quite whimsical enough for you, perhaps you’d fancy some planetary fanfiction? NASA links to “The Terminator”, a short story capturing a slice-of-life on one of the TRAPPIST-1 planets. It hinges on the notion that the planets in the system are tidally locked; like our moon always shows the same face to our planet, one side of these worlds always faces their sun. Scientists have said that it’s possible the planets are positioned that way, with a light side and a dark side—which could make for some interesting life forms and some very weird weather patterns—but for now they’re not certain.

Another story—short, but powerful—imagines a future where the new system has become a golden land of opportunity. If these worlds are habitable, will we ever inhabit them? They may be relatively close by cosmic standards—just 40 lightyears away—but heck, we haven’t even figured out how to get to Mars yet. For now, this science-fiction is pure fantasy.

And NASA isn’t alone in creating delightful content for these curious planets. Thursday’s Google Doodle is downright adorable:

Notice the new @GoogleDoodles? It's about the 7 Earth-sized planets we discovered around nearby star! Get the news: https://t.co/G9tW3cJMnV/ pic.twitter.com/dOHB0bLqXn

— NASA (@NASA) February 23, 2017

If you’re too cool for short stories and whimsical videos (you’re not), the site is also bursting with all of the knowledge NASA has to share about the seven planets and their tiny star. For more details, you’ll have to be patient: scientists will continue to observe the system with space telescopes like Kepler, Spitzer, and the Hubble to find out as much as they can. When the James Webb telescope launches in 2018, it could actually measure the temperature of the planets and decipher the chemical compositions of their atmospheres. That could tell us whether the three planets that sit in TRAPPIST-1’s habitable zone actually hold liquid water.

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Planet-hunters are always on the lookout for worlds that look like Earth—rocky planets that are not too hot and not too cold for liquid water to flow on the surface. Now scientists have hit the jackpot, discovering seven Earth-size exoplanets orbiting a single star just 39 light-years away.

The star, named TRAPPIST-1, was thought to be home to three exoplanets. But with the help of a variety of observatories—including the Transiting Planets and Planetesimals Small Telescope (a.k.a. TRAPPIST, the star’s namesake), the Very Large Telescope in Chile, and NASA’s Spitzer Space Telescope—researchers found four more planets in the system. The planets were discovered as they passed in front of the star, blocking some of its light from Earth’s point-of-view.

“It’s the first time we’ve found so many Earth-sized planets in a single system,” says Emmanual Jehin, a co-author on the study, which was published today in Nature.

Five of TRAPPIST-1’s planets are quite similar in size to Earth, while the other two are a bit smaller than our own world. Their densities suggest that six of the exoplanets are made of rock; the seventh and most distant may be an ice world.

The three exoplanets closest to the star are thought to be too hot to harbor much surface water, and the seventh may be too cold. However, temperatures may be just right on the fourth, fifth, and sixth planets; if they have Earth-like atmospheres, they could host oceans, lakes, and rivers. And where there’s water, there’s a possibility of life as we know it.

Life around a red dwarf?

Six of the planets orbit pretty close to their star, so their “years” last two weeks or less. It works out, though, because TRAPPIST-1 is a small, dim star called a red dwarf, so the planets aren’t as scorched as they would be in our own solar system.

“It’s a very small, very compact system,” says Jehin. “The seven planets are all included well inside the orbit of Mercury.”

Gravity could be doing weird things to the planets in this mini solar system. Because they’re squeezed in so close, each planet gravitationally tugs on its neighbors, potentially distorting its core and generating heat—this process, called tidal heating, is how ice worlds like Europa and Enceladus developed liquid inner oceans.

But tidal locking could be a problem in TRAPPIST-1. Like Earth’s moon, these planets likely always present the same face toward their star, resulting in a hot side and a cold side. That could potentially make the planets less welcoming to life.

Another potential problem is that astrophysicists suspect that young red dwarf stars are tumultuous, frequently spewing stellar material into space. Those solar flares could irradiate nearby exoplanets—burning off their atmospheres, eliminating the water supply, and destroying life’s chances.

Jehin, however, says more research is needed into red dwarf behavior. The team thinks the planets may have formed further from the star, then migrated closer, which may have kept them safe from any rebellious activity from when the star was young.

Plus, says Jehin, “this star is extremely quiet compared to other very small stars. It’s very calm compared to Proxima Centauri, for example…If we’re optimistic, at least five of the planets—maybe not the first and maybe not the last—but at least five could have some liquid water on the surface, if they have atmospheres and the right pressures.”

Life behind Earth

Even if the TRAPPIST-1 planets turn out to be nothing but dry, airless rocks incapable of supporting life, today’s findings bode well for the search for other Earthlike exoplanets.

Approximately 85 percent of the stars in our galaxy are red dwarf stars. So if they’re anything like TRAPPIST-1, that could add up to a whole lot of Earth-size exoplanets.

Plus, notes astronomer Ignas Snellen in an independent commentary in Nature, for every transiting exoplanet our telescopes have detected, there may be 20 to 100 times more that don’t orbit their stars on a pathway that comes between Earth and the star.

In other words, there could be tons more planets out there that we can’t see with our most common planet-hunting equipment.

Slated for launch in 2018, NASA’s Transiting Exoplanet Survey Satellite should help track down some more of these hidden worlds. It will study 200,000 of the brightest stars in the sky, looking for the telltale shadows that indicate an exoplanet is crossing in front of its star.

And we may soon be able to learn more about the TRAPPIST-1 planets themselves. After the James Webb Space Telescope launches in late 2018, it may be possible to analyze the exoplanets’ atmospheres and climates, indicating whether they might be home to living organisms—or at least the necessary ingredients of life as we know it.

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