Astronomers have found a Jupiter-mass world orbiting a brown dwarf that orbits a star.
The post Exoplanet or Exomoon? New Contender Elicits Skepticism appeared first on Sky & Telescope.
Since the discovery of the first world beyond the solar system in the 1990s, astronomers have become adept at spotting extrasolar planets, or exoplanets. But while NASA's exoplanet catalog has burgeoned to over 6,000 confirmed entries, moons around these worlds, known as exomoons, have proved elusive.
In fact, we have failed to make a single confirmed discovery of an exomoon despite being certain that just as the planets of the solar system have their own natural satellites, worlds in other star systems must have them too.
Now, this controversial drought of exomoons may have become even more confusing and, frankly, weird. That is because while studying a strange star system called CD-35 2722 with the Very Large Telescope (VLT), astronomers have discovered an object that could be an exomoon, or it could be something that forces us to rethink our very definition of what a "moon" is and what a "planet" is.
The star CD-35 2722 is located around 73 light-years away and has around half the mass of the sun. It is orbited by a "failed star" or brown dwarf. These stellar bodies get their unfortunate nickname because they form like other stars but fail to gather enough mass to trigger the fusion of hydrogen to helium in their cores. In terms of mass, brown dwarfs are more massive than the largest gas giant planets, but smaller than the smallest stars, usually with around 13 to 80 times the mass of Jupiter, or around 0.013 to 0.08 times the mass of the sun.
The newly discovered object in CD-35 2722 is certainly moon-like, but rather than orbiting a planet as the moons in the solar system do, it orbits the system's brown dwarf.
"This system is somewhat hard to define using solar-system-based words like 'planet' and 'moon.' The exosatellite is clearly massive enough to be a planet, but it does not orbit a star, though it orbits an object that orbits a star," team leader Kevin Hoy of the Universidad Diego Portales and the Millennium Nucleus of Young Exoplanets and their Moons (YEMS) in Chile, said in a statement.
"Being the third wheel in this system makes us want to call it a moon, even if it is nothing like the small, rocky moons we have in our system."
The team's research was published on Wednesday (July 22) in the journal Nature.
The team currently isn't able to definitively claim this object in CD-35 2722 is an exomoon, because that would require really nailing down a new definition of what a moon is.
"The satellite we report is a giant gaseous body orbiting a highly massive companion, itself several times the mass of Jupiter. We have a clear delineation between the planets and the sun in the solar system, so defining things like moons is simple," team member Alice Zurlo of the Universidad Diego Portales said. "In the CD-35 2722 system, where we are blurring the lines between stars, planets, and moons, the whole thing becomes more complicated to describe."
Zurlo and colleagues can, however, confidently claim this is an exosatellite, meaning it is a first-of-its-kind detection no matter what the future holds for its classification.
It is hoped that the Extremely Large Telescope (ELT) currently under construction in Chile, will make a massive impact in the hunt for exomoons, and now, other exosatellites.
Until these objects begin to be uncovered, one thing this discovery re-emphasizes is something that astronomers have been gleefully discovering ever since the first exoplanet was spotted: planetary systems come in a variety of diverse, weird and wonderful forms.
Editor’s Note: Astrobites is a graduate-student-run organization that digests astrophysical literature for undergraduate students. As part of the partnership between the AAS and astrobites, we occasionally repost astrobites content here at AAS Nova. We hope you enjoy this post from astrobites; the original can be viewed at astrobites.org.
Title: Mars as an Exoplanet: Lessons from a Planet at the Edge of Habitability
Authors: Stephen R. Kane et al.
First Author’s Institution: University of California, Riverside
Status: Published in PSJ
If you’re a fan of Stranger Things like me, you’ll know of the Upside Down: a mirror world similar to our own, but with very different rules. Imagine Mars in the Upside Down, where it is no longer our next-door neighbor but a planet hundreds of light-years away. An astronomer on this Upside Down Earth would be looking at a distant speck with a transit signal barely distinguishable from noise. In this world, Mars would no longer be familiar but completely foreign, with unknown properties. Kane et al. suggest that treating Mars as if it were a stranger is a useful way to think about exoplanet science today.
JWST is hunting for atmospheres on small rocky planets around other stars. However, only a select few Mars-like exoplanets have been discovered (Figure 1). This is because sub-Earth planets are small and hard to detect, testing the bounds of current technology. The ones that have been discovered, such as TRAPPIST-1h and Kepler-138b, were detected due to favorable geometry. They happen to orbit very close to a low-mass star or sit in resonant multi-planet systems, which amplify the signal we are looking for. True Mars analogs with low flux and moderate orbital periods remain out of reach. This is precisely what makes Mars itself so important scientifically — it is the only planet of this type we can study up close.
Figure 1: A plot of confirmed exoplanets by mass and radius. Most confirmed exoplanets are larger and more massive than Earth. Mars-like planets (dots in the blue box) are rare in confirmed exoplanet detections. [Kane et al. 2026]
We know a lot about Mars in comparison to other planets thanks to rovers (such as Curiosity and Perseverance), atmospheric orbiters (such as Mars Atmosphere and Volatile EvolutioN and the Mars Orbiter Mission), and other science missions (Figure 2). We know it once had water features with neutral pH and favorable chemistry for life from sedimentary evidence at the Gale and Jezero craters. We know its atmosphere is 95% CO2 with a surface pressure less than 1% of Earth’s. We know it once had an active magnetic dynamo, but the dynamo died out about 4 billion years ago, leading to solar wind steadily stripping away Mars’s atmosphere over time.
Figure 2: Earth and Mars to scale, showing their internal structures and atmospheres. Despite being neighbors, Mars is dramatically smaller with a thin CO2 atmosphere, similar to the planets JWST is struggling to characterize. [Kane et al. 2026]
JWST is currently studying the small rocky TRAPPIST-1 planets and is finding little evidence of atmospheres. The authors of today’s article explore the idea that these exoplanets are similar to Mars and perhaps are undergoing processes that strip away their atmospheres and create optimal conditions for life only for short durations. Using Mars as a blueprint, the authors show how we can better understand exoplanet processes, including volatile delivery and loss, photochemistry, climate evolution, obliquity forcing, planetary architecture, and intrinsic magnetism. For example, measurements of noble gases directly fingerprint Mars’s atmospheric escape process, and the authors argue these give us a calibration framework for interpreting future exoplanet spectra.
The upcoming Nancy Grace Roman Space Telescope’s microlensing survey will start revealing how common true Mars analogs actually are throughout the galaxy, while the future Habitable Worlds Observatory will attempt direct imaging of nearby candidates with unprecedented precision. Together, these missions will tell us whether Mars-like outcomes (brief habitability, catastrophic atmospheric loss, barren surfaces, etc.) are the default fate for small rocky planets. Interpreting that data will require the exact framework this article builds: one grounded in the only Mars analog we can study in detail.
Original astrobite edited by Sandy Chiu.
About the author, Ben Sherwin:
I am a physics PhD student and a National Science Foundation Graduate Research Fellow at Stanford University, working with Josh Frieman. I am interested in theoretical and observational cosmology, specifically in cross-correlations between the cosmic microwave background and tracers of large-scale structure.
The post What if Mars Were a Stranger (Thing)? appeared first on AAS Nova.
A team of astronomers have discovered helium escaping from a rocky planet, marking the first detection of an atmosphere on a rocky world.
The post First Atmosphere Detected on a Terrestrial World appeared first on Sky & Telescope.
Astronomers have found the strongest evidence yet that a rocky planet beyond our solar system has managed to hold onto an atmosphere — a crucial ingredient for life as we know it.
The discovery marks the first time scientists have detected an atmosphere surrounding a rocky planet orbiting in the habitable zone of another star, the region around a star where temperatures could enable liquid water to exist on a planet's surface. The findings, published July 16 in the journal Science, could help astronomers narrow the search for potentially habitable worlds beyond our cosmic backyard.
"It's absolutely exciting," Edward Schwieterman, associate professor of astrobiology at the University of California, Riverside, who was not involved in the study, told Live Science in an email. "We are getting closer to studying the atmospheres of worlds that could plausibly harbor life, with evidence of that life embedded in their observable spectra."
The planet, known as LHS 1140 b, lies about 48 light-years away from Earth and orbits a small, cool red dwarf star. At roughly 5.6 times Earth's mass, the exoplanet is classified as a super-Earth: a rocky planet larger than our own but much smaller than gas giants like Neptune.
It receives less than half the sunlight Earth gets, giving it an estimated surface temperature of around minus 53 degrees Fahrenheit (minus 47 degrees Celsius), according to previous estimates not accounting for an atmosphere. That makes the planet cold, but in the range astronomers consider potentially habitable.
Scientists have discovered thousands of exoplanets over the past few decades, including many rocky worlds. But determining whether those planets have atmospheres has proven far more difficult, because atmospheres around rocky planets are incredibly thin compared with those of giant planets, making them much harder to detect across vast cosmic distances.
Instead of looking for the atmosphere directly, the researchers behind the new study searched for a subtle clue that one existed: helium gas leaking into space. Using the WINERED spectrograph on the Magellan Clay Telescope in Chile, the team watched LHS 1140 b cross in front of its star and let a sliver of starlight filter through the planet's atmosphere on its way to Earth. As it did, the team looked for a tiny dip in the star’s light at the exact wavelength of infrared light that helium blocks — a telltale sign that gas was streaming off the planet and into space.
The prediction rested entirely on a mathematical model that had never been confirmed for a rocky planet. However, in September 2024, the team caught LHS 1140 b and a smaller, hotter neighboring planet, LHS 1140 c, transiting their star on the same night, less than 40 minutes apart. The researchers detected a clear helium signal from LHS 1140 b, while LHS 1140 c showed nothing.
The contrast matters: LHS 1140 c orbits much closer to its star than LHS 1140 b does and receives roughly five times the radiation, yet it's also smaller and less gravitationally bound — conditions that should make any escaping gas easier, not harder, to spot. Finding nothing there suggests LHS 1140 c's atmosphere was stripped away long ago, while LHS 1140 b, sitting farther out in cooler, calmer conditions, has managed to hold onto its own.
The discovery addresses a question astronomers have been working to answer for decades.
"Twenty years ago we wondered whether other terrestrial-type planets even existed," study co-author Robin Wordsworth, a professor of Earth and planetary sciences at Harvard, said in a statement. "Then we learned they're common, and found some in the habitable zone. The next question was whether any of them had managed to keep an atmosphere. Now we know at least one has."
The find is especially notable because red dwarf stars like LHS 1140 can bombard nearby planets with high-energy radiation capable of stripping atmospheres away over time. Based on the star's estimated age of at least 3.1 billion years, the researchers say LHS 1140 b's atmosphere has likely persisted despite that bombardment, suggesting some rocky planets around these common stars can hang onto their atmospheres for far longer than once assumed.
But the researchers caution that detecting helium does not mean the planet is inhabited — or even that it is habitable. The observations reveal only the planet's thin upper atmosphere, not its full composition. Scientists still don't know whether LHS 1140 b has oxygen, carbon dioxide, water vapor or other gases that could make its surface more Earth-like and hospitable to life.
Instead, the discovery opens a new way to study distant rocky worlds.
"The study demonstrates that, at least in some cases, we will be able to begin characterizing the atmospheres of potentially habitable planets," Schwieterman said. "If only rocky planets orbiting Sun-like stars retained atmospheres, we might have to wait one to two decades for the launch of the Habitable Worlds Observatory to search for biosignatures on rocky planets. I'm certainly excited about what comes next!"
Future observations will aim to determine what the rest of LHS 1140 b's atmosphere is made of and investigate whether it may harbor oceans or other features associated with habitability.
If there’s extraterrestrial life anywhere in the galaxy, chances are, it could be on LHS 1140b.
Astronomers have found that the exoplanet 48 light years away is spewing helium into space, a strong sign that it harbors a robust atmosphere, they reported in a new study published in the journal Science.
And that’s not all: it’s also a rocky world like our own, and orbits within its star’s habitable zone, the region around a star where a planet can maintain liquid — and possibly life-harboring — water on its surface.
If their findings are borne out, then it’s the first ever Earth-like exoplanet we’ve seen with an atmosphere stable enough to support life — and could vindicate the belief that there’s a whole host of similar planets out there, rather than our own being a rare anomaly in the cosmos.
“When there’s one, there’s more in exoplanets,” Sara Seager, an astrophysicist at MIT who was not involved in the study, told the New York Times. “Hopefully this is the start of something new.”
“At this point, we have absolutely no evidence for life on the planet,” lead author Collin Cherubim, a planetary scientist at Harvard University, added to the newspaper. “But we think all of the really important, essential ingredients are there.”
Spotting exoplanets is rare. While we have catalogued millions of stars, we have only confirmed around 6,000 worlds outside our solar system. Finding ones with an atmosphere is even rarer, since their signals are faint compared to the light of the planet’s star. In many cases, the planets with atmospheres are gas giants, which are unlikely to support life.
A key detail is that LHS 1140b orbits a red dwarf. Planets around red dwarfs are easier to spot because the diminutive stars are fainter, meaning it’s more noticeable when a planet passes in front of them. But since they emit less heat, a potentially habitable planet needs to orbit much closer to to them than we do our Sun. That could be a problem because red dwarfs are believed to be highly volatile. A closely orbiting planet would be in danger of being battered by solar flares and other powerful outbursts, which could strip it of its atmosphere and sterilize developing lifeforms.
The astronomers, however, found that LHS 1140b has a helium-rich atmosphere despite being — or because it’s in — the star’s habitable zone, demonstrating that the volatility of red dwarfs may not be as much as a problem as once thought (though this one appears to be less active than its cousins). They used a theoretical computer model of exoplanet atmosphere evolution that tracked how lighter elements like hydrogen and helium would be ejected by the outbursts of its host star, Science explained. When they applied it to LHS 1140b, which was first discovered in 2017, it predicted that its upper atmosphere would be dominated by helium, a promising sign that it’s capable of supporting life.
“Twenty years ago we wondered whether other terrestrial-type planets even existed,” Robin Wordsworth, a professor of earth and planetary sciences at Harvard, said in a statement about the work. “Then we learned they’re common, and found some in the habitable zone.”
“The next question was whether any of them had managed to keep an atmosphere,” he added. “Now we know at least one has.”
More on space: Scientists Say They’ve Identified an Earth-Like Planet Right Next Door
The post Astronomers Thrilled After Discovering Best Spot Yet to Look for Alien Life appeared first on Futurism.
Most of the gas in the Universe is a mixture of hydrogen and helium. It's thought that the initial atmospheres of most planets also start out that way. However, over billions of years, as planets evolve, the composition of their atmospheres may shift. Hydrogen can react with other chemicals, and both it and helium can be lost to space. Venus, Earth, and Mars are thought to have second atmospheres, with their original hydrogen/helium envelopes having been lost and/or transformed.
The dynamics of loss are complicated. Lighter elements are lost more easily, but hydrogen can be protected by being incorporated into molecules like methane and ammonia. The gravity of the body can help retain some molecules, and a magnetic field can limit radiation's ability to blast material out of the atmosphere. Proximity to a star will matter too, both because of the radiation it produces and because it can heat the atmosphere and expand it to where gravity's influence is less substantial.
Given all these complications, it can be difficult to know what to expect to find on exoplanets. But a study in Wednesday's issue of Nature describes observations of helium being lost from the atmosphere of an exoplanet orbiting the star LHS 1140, about 50 light-years away. Based on the rate at which the helium is being lost, we can infer something about the remaining atmosphere.
© NASA/JPL-Caltech/T. Pyle (SSC)
This might be the closest we've gotten to finding a planet that could support life: Astronomers have detected an atmosphere around an Earth-like, rocky planet orbiting in the habitable zone around its star, a monumental first.
The rocky planet, called LHS 1140 b, is 48-light-years away from Earth and according to this new research, it has an atmosphere that contains helium. It is also the first rocky planet to have an atmosphere be detected directly. This is the first rocky planet to be found with an atmosphere that is also in the habitable zone, meaning it's at the right distance away from its star for liquid water to potentially exist on the planet. As we continue to search the cosmos for planets that can be considered "habitable," this planet checks more boxes than almost anything we've ever seen.
"We have actually detected directly the helium present in the atmosphere itself, and that's the first direct detection for any rocky exoplanet, which is really exciting … and then there's this added bonus that it's in the habitable zone, which is super exciting for astrobiology and habitability and searching for life," lead author Collin Cherubim, who recently earned his Ph.D. from Harvard University, told Space.com. "It feels kind of surreal."
Let's explore this planet and the system where it "lives."
This exoplanet, or planet outside of our solar system, was first discovered in 2017 by a team led by astronomer Jason Dittmann who is now a co-author on this new discovery.
"This planet was found like 10 years ago, and we're just now saying, okay, that's an atmosphere," Dittman told Space.com. "We're slowly narrowing the gap and checking these boxes … we're finding a planet that's rocky, a planet that's of the right temperature and now … it's like okay, we finally found one that has an atmosphere."
And being a rocky planet, "there's definitely a surface … it's made of rocks," Dittman said. What does the planet's surface look like? We can't say yet, but the researchers who found this planet's atmosphere think there's a good chance it could have water.
While it orbits a red dwarf star, which is smaller and cooler than the sun, it orbits closer than we do to our star, maintaining a temperature that keeps the planet in the "Goldilocks zone" where liquid water could exist on its surface.
"It probably also has a lot of water," Cherubim said. "If it has some amount of atmosphere that can provide a bit of a greenhouse effect, which we know that it does now … it will very likely be what we consider to be habitable conditions on Earth, and conditions that would likely support liquid water."
So is it Earth-like? While it's certainly not an Earth copy, this planet can be considered Earth-like in two main ways, Cherubim shared. One: its overall composition. The planet is rocky, likely with an iron core and (now we know) it has an atmosphere. And two: the planet's temperature is just right for liquid water, which is necessary for life at least as far as we understand it on our planet.
The discovery of the first exoplanet was confirmed just over 30 years ago. Since then, scientists have found over 6,000 exoplanets and counting. And while a few rocky planets have been found in their star's habitable zone, it wasn't until now that an atmosphere has been confirmed around a rocky planet in the habitable zone.
One reason why scientists have had a hard time finding such planets with atmospheres is their stars. LHS 1140 b orbits the most common type of star, a red dwarf, which is about one-third the size of our sun. This type of star remains active for a lot longer than stars like our sun. This activity means it releases bursts of extreme radiation like solar flares and coronal mass ejections. And typically, the extreme radiation around these stars totally strips the atmospheres from the planets orbiting them, so astronomers have wondered if planets orbiting these stars can have an atmosphere at all.
"This discovery is a big deal because it's showing that at least this rocky planet has retained an atmosphere over billions of years," Cherubim said. It's "a bona fide, robust way of saying yes, atmospheres can survive on rocky exoplanets."
It's possible that other gases beyond helium are in the planet's atmosphere, and it's possible that some of its atmosphere was previously stripped away by its star's radiation. But the red dwarf that this planet orbits is roughly 6 billion years old, a few billion years older than the age at which their extreme radiation activity begins calming down. So while some helium is still slowly escaping the planet's atmosphere over time, the team expects the planet to retain an atmosphere, Dittman shared. After all, even Earth's helium is slowly escaping our own atmosphere.
To prove that this planet has an atmosphere, the team started with a prediction that Cherubim made during graduate school. It all started with a theoretical model and a sneaking suspicion that there must be rocky exoplanets with atmospheres other than Earth.
"This came out of a very specific prediction from a planetary evolution model that I actually developed myself, from scratch, from first principles, for my Ph.D. as a theorist, and I made a very specific prediction about this planet," Cherubim said. "And then I went out and did a pretty unexpected, weird thing using this technique that's typically reserved for observing giant planets, and I used it for a rocky planet, which nobody has done before.
"And lo and behold, I made this measurement that was actually consistent with my prediction. And it was really nice to kind of close the whole loop of the scientific method."
The team took the theoretical model that Cherubim developed in graduate school and put it to the test using the Warm Infrared Echelle (WINERED) Spectrograph on the Magellan Observatory in Chile. And with their observations, they were able to see LHS 1140 b and another planet both transit, or pass in front of, their star in the same night. With this spectrographic data, they could identify the signatures of molecules in the atmospheres of these planets as they passed in front of the star. And while one planet yielded no results, this planet showed a direct, undeniable helium signature.
When looking at a planet that is rocky, has an atmosphere, and is in the habitable zone (meaning it could have liquid water), the question of life comes up quite quickly.
But the researchers don't have enough data to make that conjecture. "I'm not claiming this planet has life," Cherubim made clear. With further investigation, scientists could better understand what else might be in this planet's atmosphere, and they could confirm if it has water. Further observations might not be able to confirm habitability or identify any life on the planet, but they could at least help us to better understand planets like this.
With this being the first planet of its kind discovered, further exploration will help us to put the pieces together. But it is certainly a major step forward in the eternal human quest to answer the question: are we alone?
This work was described in a study published in the journal Science.
Two teams of astronomers independently discovered a third giant gas planet orbiting in the famous Beta Pictoris system.
The post Famous System Has a Third Planet: Beta Pictoris d appeared first on Sky & Telescope.
It has taken over ten years, but astronomers have finally won a prolonged game of cosmic hide-and-seek with a planet hiding around the star Beta Pictoris. The extrasolar planet, or exoplanet, is known as Beta Pictoris d. It is found 63 light-years away and has two planetary siblings, which were caught some time ago.
This new exoplanet is 100 times fainter than its sibling Beta Pictoris b, which was the first planet discovered in the system. That makes Beta Pictoris d the faintest exoplanet ever seen from Earth.
Like its previously discovered sibling, Beta Pictoris d is a gas giant. However, unlike Beta Pictoris b and Beta Pictoris c, it is much further away from its parent star and is thus much cooler than its siblings. The newly discovered world is also smaller than the previously seen world around Beta Pictoris. While both Beta Pictoris b and Beta Pictoris c have around 10 times the mass of Jupiter each, Beta Pictoris d has only around 2.4 times the mass of the solar system's most massive world. That makes it one of the lightest exoplanets ever directly imaged by a ground-based telescope.
"Planet d, it seems, has been playing a game of hide-and-seek with us for over a decade, and only now can we say ‘found you!’" team member Jayne Birkby an astronomer at the University of Oxford in the UK, said in a statement.
The discovery of Beta Pictoris d helps clear up a puzzle regarding a disk of dust and debris in this planetary system, which is theorized to be made of the leftovers of planet formation. That is because this newly found world has exactly the right mass and location needed to explain both the odd shape of this debris disk and its location.
The team behind this discovery wasn't initially looking for a third planet around Beta Pictoris. Instead, they were simply attempting to learn more about the system's first planet.
"This was a serendipitous discovery," team co-leader Ben Sutlieff, an astronomer at the University of Edinburgh said. "We initially wanted to look more at a known planet in the system, Beta Pictoris b, to see how it changed over time."
That was until they spotted telltale signs of another planet around the same star. Delving back into 11 years of archival data, the team found the third planet lurking in various images.
To consider how impressive it is to directly image a planet outside the solar system, consider that of the over 6,000 worlds in NASA's exoplanet catalog, less than 100 were discovered using direct imaging. Such detections are so tricky because they require picking out the thermal glow of a planet from the glare of its parent star.
Catching a direct image of an exoplanet as faint as Beta Pictoris d is a major step forward for this technique.
"The new planet is 100 times fainter than Beta Pictoris b, the famous planet in the same system, making it the faintest exoplanet ever imaged directly from Earth," team co-leader and European Southern Observatory researcher Markus Bonse said.
The discovery of Beta Pictoris d makes the Beta Pictoris system just the second in which more than two worlds have been directly imaged. The first was HR 8799, which is located around 133 light-years away.
"Systems with multiple directly imaged exoplanets are the 'holy grails' of discoveries, because they can teach us a lot about what different exoplanets are like in the same formation environment," Sutlieff said
Thus, the discovery of Beta Pictoris d via direct imaging should encourage further direct imaging of planetary systems which may also harbor faint planets. This is an investigation that could be picked up by the Extremely Large Telescope (ELT), currently under construction in the Atacama Desert of northern Chile.
"Planets seem to have friends," team member Beth Biller, of the University of Edinburgh in the UK, said. "Many of the famous directly imaged exoplanet systems seem to have multiple giant planets in the same system, and likely there are even more lower-mass planets hiding in these systems that might be revealed with instruments on the ELT."
The team's research was published on Wednesday (July 15) in The Astrophysical Journal Letters.
"Rogue" Neptune-size worlds might not roam the galaxy totally on their own, just very far away from their parent stars.
The post "Rogue" Neptunes Are Detached But Not Alone appeared first on Sky & Telescope.
Editor’s Note: Astrobites is a graduate-student-run organization that digests astrophysical literature for undergraduate students. As part of the partnership between the AAS and astrobites, we occasionally repost astrobites content here at AAS Nova. We hope you enjoy this post from astrobites; the original can be viewed at astrobites.org.
Title: Carbon Cycle Imbalances on Arid Terrestrial Planets with Implications for Venus
Authors: Haskelle T. White-Gianella and Joshua Krissansen-Totton
Authors’ Institution: University of Washington
Status: Published in PSJ
When discussing the habitability of planets, we usually focus on the habitable zone, the region around a star where a planet can host a temperature suitable for supporting liquid water on its surface. Yet, being in the right place doesn’t necessarily guarantee that a planet will be habitable.
A planet also needs the right atmospheric composition to sustain the necessary temperatures for hosting liquid water. A key mechanism found on Earth for maintaining this composition is the geologic carbon cycle, which acts as a built-in climate control system. This cycle begins with volcanic eruptions releasing carbon dioxide (CO2), which then dissolves in rainwater and forms a weak acid that weathers rocks on continents. The weathering products wash into oceans, where they form carbonate rocks, locking carbon away. Eventually, plate tectonics recycles some of that carbon back to volcanoes. The weathering process works faster when the planet is warmer, thus regulating the amount of CO2 and stabilizing the climate over long periods of time (but it should be noted that it can take up to a few hundred thousand years to rebalance this slow carbon cycle through the weathering process).
An important caveat is that the weathering process requires sufficient liquid water on the planet’s surface, so what happens in the case for planets with shallower oceans? Low-mass M dwarfs, the most common type of star found in the galaxy, are expected to host less-massive disks and therefore lower water inventories for forming planets. If more “dry” planets are indeed a more likely outcome of planet formation, we’d want to know how their arid conditions influence their long-term evolution and habitability.
The authors built a model that tracks how water and CO2 move between a planet’s interior, oceans, and atmosphere over 4.5 billion years. The model notably includes the following:
The model tests for four initial surface water inventories (0.1%, 1%, 10%, and 100% of Earth’s oceans) and then simulates how the surface water, atmosphere, and climate evolve over time.
The models reveal that planets require at least 20–50% of Earth’s ocean mass to maintain a balanced carbon cycle. Below this threshold, the carbon cycle becomes unbalanced, leading to devastating consequences for habitability (Figure 1).
Figure 1: Final surface temperature after simulating 4.5 billion years of evolution as a function of initial water inventory for Earth-like planets. Each dot represents a model run with different assumptions (total carbon inventory, temperature dependence of weathering, soil age, etc.). The yellow region shows where most simulations result in uninhabitable surface temperatures from an unbalanced carbon cycle, and the cyan region shows where most simulations result in habitable surface temperatures and a balanced carbon cycle. The left and right plots show the results for two different parameterizations of the deep water cycle implemented in the model. [White-Gianella & Krissansen-Totton 2026]
Looking within the solar system, the results offer an explanation for how a potentially habitable Venus could have transitioned into its current inhospitable state. If Venus had formed with an initial water inventory below this critical threshold of 20–50% of Earth’s ocean mass, then its carbon cycle would have become unbalanced, creating the CO2 inferno seen on Venus today.
In future exoplanet studies, telescopes like the Habitable Worlds Observatory might detect ocean glint (specular reflection from liquid water) or measure land fraction from light curves. Finding a planet in the habitable zone but with limited ocean coverage would likely be bad news, as the planet could be quietly losing its grip on habitability. Astronomers may want to be more careful when looking at seemingly promising planets within their habitable zones.
Original astrobite edited by Natalie Price.
About the author, Jared Bull:
I am a 2nd-year PhD student at Johns Hopkins University. I study brown-dwarf variability and am interested in using time-series observations to uncover dynamic processes within their atmospheres. In my free time I like to read, cook, and do astrophotography.
The post Can Arid Planets Keep Their Cool? appeared first on AAS Nova.
Clouds formed from vaporized rock could create the ultimate thermal insulation on one of the most common types of exoplanets discovered so far — the sub-Neptunes — raising temperatures so high that these worlds' solid surfaces melt and turn into oceans of magma.
"This work takes us one step closer to answering the question of what these mysterious worlds are made from," said astronomer Luis Welbanks, of Arizona State University, in a statement.
Sub-Neptunes are planets larger than Earth but smaller than Neptune. They are especially mysterious since we do not have a world of this type in our solar system. They are thought to contain a rocky core surrounded by a deep atmosphere, but not much else is known about their composition and structure. Their atmosphere could be hydrogen-rich like Jupiter's, or it could be abundant with water vapor and carbon-based organic molecules. In some cases, they might even be habitable under the hycean world paradigm, wherein a thick hydrogen atmosphere encases a global ocean of liquid water.
The James Webb Space Telescope (JWST) is busy probing the atmosphere of several sub-Neptunes to try and learn more about their bulk composition because their atmosphere should be representative of what such planets are made from, but results so far have been inconclusive.
Atmospheres of sub-Neptunes are deep and dense, meaning crushing pressures close to the boundary between the atmosphere and the solid body of the world can turn minerals into vapor that forms clouds. These minerals include aluminium oxide, iron, magnesium silicate, manganese sulfide, potassium chloride, sodium sulfide and zinc sulfide.
Using detailed computer simulations, a team led by Sagnick Mukherjee of Arizona State University explored what effect these clouds could have on both the surface and atmosphere of a sub-Neptune.
They showed that when these mineral clouds form deep down, they act as efficient insulating blankets that trap heat (and lots of it) leaking out from the core of the planet.
"Among the sub-Neptunes currently being studied with JWST, we were amazed to find that cloud-driven heating can raise the temperature at the planet's atmosphere–interior boundary by roughly over 1,400 to 2,600 degrees Celsius [2,550–4,712 degrees Fahrenheit]," said Mukherjee.
At the same time, because heat is being prevented from escaping, the upper atmosphere cools noticeably.
With all that heat retained close to the surface, the rock begins to melt.
"For some of the planets we modeled, that extra heat is enough to melt the planet's surface, creating a magma ocean," said team-member Matthew Nixon of Arizona State University.
These potential magma planets include GJ 1214b, which orbits a red dwarf star 48 light-years away. At one time it was thought to be a cool water-world, but JWST's discovery in 2025 of metallic vapors and carbon-dioxide haze in GJ 1214b's atmosphere rule this out, and now it seems that its surface, undetectable beneath the thick atmosphere, could be completely molten.
However, the presence of magma oceans opens up possibilities for more complex atmospheric chemistry. Gas seeps out of the magma and diffuses into the atmosphere, in theory enriching it in oxygen, silicon hydride and silicon monoxide, while going the other way the magma absorbs ammonia, methane and water vapor from the atmosphere. In other words, the atmosphere becomes enriched by material from underground, while also becoming depleted in some gases that astronomers would expect to see in greater abundance.
This means that JWST's attempts to learn about the bulk composition of a sub-Neptune exoplanet from the spectrum of its atmosphere could be skewed by this exchange of gases between a magma ocean and the atmosphere. The extra heating deep down will also impact the future of these sub-Neptune planets, since the extra heat will keep their lower atmosphere bloated and prevent the planet from contracting over billions of years.
If the findings are correct, they could place a huge obstacle on sub-Neptunes being habitable. Even if the boundary between the atmosphere and solid body of the planet isn't hot enough to form magma, it would still render the surface too hot to support liquid water or life.
The findings were published on July 8 in Astrophysical Journal Letters.
WD 1856 b is the only confirmed case of a planet that survived the death of a Sun-like star. It’s a Jupiter-size world orbiting a white dwarf—the burned-out remnant of a Sun-like star. Now, a team of astronomers has used the James Webb Space Telescope to take a closer look at this planet for the first time, and what they found makes an already strange system even stranger.
WD 1856 b was an accidental discovery. Astronomers pointed the TESS observatory at a sample of roughly 2,000 white dwarfs in 2020. These stars are the remains of a Sun-like star that have already gone through a red-giant phase, leaving behind an Earth-size body that’s primarily composed of elements like carbon and oxygen. The TESS team was searching for small objects like comets or asteroids that might transit across the face of these dead stars.
What they found in the WD 1856 system was a gas giant. “As soon as they looked at it, they said, okay, that’s weird,” said Christopher O’Connor, a theoretical astrophysicist at Cornell University and co-author of the recent Nature study on WD 1856 b.
© NASA, ESA, CSA, R. Crawford
A recently discovered exoplanet only 25 light years away resembles our own planet a lot more than once thought.
The distant world, dubbed GJ 3378b, orbits inside the habitable zone of a red dwarf star — a type of star that is much smaller and cooler than our Sun — where temperatures are just right for liquid water to form on the surface.
But initially, its case for potentially supporting life beyond that looked grim. Astronomers suspected it was a rocky world, but its mass was at least five times more than Earth — or what astronomers called a “super-Earth.” Along with its incredible surface gravity, such a heavy world would possess a crushing atmosphere that would smother any chance of hosting life.
That no longer appears to be the case, however. In a new study published in The Astrophysical Journal, researchers from the University of California, Irvine, took a second look at the exoplanet, finding that it’s a much more manageable twice the mass of Earth. Combined with its proximity to our solar system, it’s one of the most tantalizing nearby candidates for potentially supporting life yet.
“This one’s exciting,” lead author Paul Robertson, a UC Irvine associate professor of astronomy, said in a statement about the work. “It’s one of our closest cosmic neighbors. 25 light-years sounds like a long way, but the Milky Way is about 100,000 light-years across, so in that respect it’s our next-door neighbor.”
There’s more detective work that needs to be done before we know how hospitable to life GJ 3378b is. The biggest question mark is its atmosphere. Does it have one, and is it robust enough to protect against the radiation of its star? And how much pressure does it exert?
It’s a delicate balance. “If you scale the Earth down to the size of an apple,” Robertson explained, “its atmosphere would be about as thick as the skin of the apple.” This is just the right amount to support liquid water and have breathable air, while still providing protection against space radiation, he added.
There’s also a raging debate in astronomy over whether red dwarf systems are habitable at all. These stars are believed to be highly volatile, regularly unleashing powerful solar flares. Because their habitable zones are smaller, that puts a potential life-supporting realm much closer to these outbursts, which could strip them of their atmosphere and sterilize any burgeoning life. Being so close to the star also means that any such planets are likely to be tidally locked, in which the star’s gravity prevents them from rotating so that one side is facing the star at all times.
More on space: Saturn’s Icy Moon Is the Perfect Place to Settle, NASA Scientist Argues
The post Scientists Say They’ve Identified an Earth-Like Planet Right Next Door appeared first on Futurism.
Microlensing surveys have discovered plenty of regular exoplanets, but more surprisingly, they’ve also turned up many solo Neptunes with no star nearby. New research suggests that first impressions might be deceiving, however, and that at least some of these planets might not be so alone: they just have a complicated family history.
There are simply too many Neptune-like exoplanets in our galaxy. Or at least that’s the current feeling astronomers get from gravitational microlensing surveys, which look for exoplanets during short-lived magnification events caused by chance alignments between stars. These surveys have now found about a dozen so-called “free-floating” planets, and while this doesn’t sound like that many, running the numbers reveals that this tiny sample implies that there are about two free-floating Neptune-size planets for every star in the galaxy.
An illustration of how exoplanets are found via microlensing. The broad first bump is caused by the host star magnifying the light from a background star; the narrow second bump is caused by the planet acting as a lens as well. “Free-floating” planets create only one bump. [Adapted from NASA, ESA, and A. Feild (STScI)]
However, new research by Sam Hadden (Canadian Institute for Theoretical Astrophysics) and Yanqin Wu (University of Toronto) presents an alternative idea: what if at least some of these free-floating planets aren’t fully on their own, but instead remain estranged but weakly bound to their parent stars?
Two celestial objects need to align nearly perfectly in order to create a microlensing pulse that we can detect. For an exoplanet orbiting a star, we should observe two of these pulses: one when the host star drifts in and out of alignment with a background star, and one when the nearby bound planet does the same. In the case of a free-floating planet, there’s only one pulse, and we therefore assume that there is no host star. Hadden and Wu noticed that since the alignment has to be so precise for microlensing to occur, it’s possible that a seemingly free-floating planet is simply widely separated from its host star, and the star managed to dodge the magnification effect. In other words, these planets might not be free floating at all, just on wide and eccentric orbits.
The orbital evolution of a five-planet system that undergoes planet–planet scattering. Each line represents one planet; note that in the end two are ejected, two end up on wide detached orbits, and the fifth ends up on a tightly bound inner orbit. Click to enlarge. [Hadden & Yu 2026]
They found that both types of simulations readily created the “detached” objects needed to mimic free-floating planets. In fact, the most common outcome was for two or three planets to be bullied into far-out orbits by a planet that then plunges onto a tight inner orbit extremely close to the star.
Though the authors caution that this process likely doesn’t explain all of the free-floating planets observed to date, this is an exciting model that would dramatically lower our estimates of the number of Neptunes roaming alone between the stars.
“Free Floating or Merely Detached?,” Sam Hadden and Yanqin Wu 2026 ApJ 1000 70. doi:10.3847/1538-4357/ae6508
The post Detached but Not Alone appeared first on AAS Nova.
A hefty "super Earth" lurking in one of the closest star systems to our planet may be much better suited to supporting extraterrestrial life than scientists initially thought, a new study suggests. The alien world's relative proximity to Earth, and the nature of its home star, make it a prime candidate for follow-up observations, researchers say.
The exoplanet, dubbed GJ 3378b, was discovered in 2024 and orbits a red dwarf star around 25 light-years from our planet. The alien world circles its star every 21.5 days at a distance around 10 times closer than Earth orbits the sun, which would make it completely inhospitable in our solar system. But because the red dwarf emits around 90% less radiation than the sun does, GJ 3378b is slap bang in the middle of this star system’s "habitable zone," where liquid water could exist on the exoplanet's surface.
Researchers initially thought that GJ 3378b was around five times more massive than Earth. If the planet is rocky like ours, it would qualify as a "super Earth" — often considered the best candidates for sustaining extraterrestrial life. However, it was hard to tell if this world had a solid surface or was actually a mini gas giant. And even if it was rocky, its immense size would probably mean that its atmospheric pressure would be crushing, making it less likely to harbor life.
But in a new study, published June 30 in The Astrophysical Journal, researchers recalculated the exoplanet's size, using the Habitable-zone Planet Finder instrument attached to the Hobby-Eberly Telescope at the McDonald Observatory in Texas. This device measures subtle wobbles in the host star, caused by the gravitational tug of orbiting planets, and can be used to calculate the planet’s mass and trajectory.
This revealed that GJ 3378b is actually only 2.3 times more massive than Earth, which almost guarantees it is a rocky world and means it could have an atmosphere with a similar pressure to our own, raising the chances that extraterrestrial lifeforms could thrive there.
While researchers have found several other exoplanets that could harbor life, the fact that GJ 3378b is so close to us makes it particularly intriguing, as it will be easier to confirm whether it is truly habitable.
"This one’s exciting," study first author Paul Robertson, an astronomer at the University of California, Irvine, said in a statement. "25 light-years sounds like a long way, but the Milky Way is about 100,000 light-years across, so in that respect it’s our next-door neighbor."
Before we get too carried away, there is still no evidence that GJ 3378b has an atmosphere or liquid water. Its proximity to its home star may mean that any atmosphere it once had was stripped away by stellar winds, similar to how solar radiation likely stripped Mars of its atmosphere and ancient oceans.
Therefore, more observations are needed. But if an atmosphere is detected, GJ 3378b would likely jump to near the front of the queue of exoplanets that researchers want to study further.
"If a planet in the habitable zone has a proper atmosphere, we can justify further research looking for biosignatures, liquid water or other signs of life," study co-author Gogod James, an undergraduate student at UC Irvine, said in the statement.
The fact that GJ 3378b orbits a red dwarf also makes it more appealing for future study because this is the most common star type in the Milky Way, so experts are keen to learn more about these stars' planetary systems and potential to nurture life.
"About 70% of stars in our galaxy are red dwarfs, so they represent the standard," study co-author Michael Endl, an astronomer at the McDonald Observatory and the University of Texas at Austin, said in another statement. "It’s really important that we understand the planet population around these stars."
NASA’s Transiting Exoplanet Survey Satellite has found two “super-puff” planets in the same system, each one as light as cotton candy.
The post Cotton-Candy Exoplanets: Two for the Price of One! appeared first on Sky & Telescope.
Using NASA's exoplanet-hunting spacecraft TESS (Transiting Exoplanet Survey Satellite), scientists have discovered a planetary system that scientists are calling "improbable." It could change how we think about the mechanisms behind planet formation.
The reason for the unusual arrangement of this planetary system is a failed star or brown dwarf designated TOI-201 c. Objects like this get the slightly unfair nickname of "failed stars" because, despite forming from a collapsing cloud of gas and dust like other stars, they fail to gather enough mass to trigger nuclear fusion of hydrogen to helium in their cores. Brown dwarfs have masses between 13 and 80 times that of Jupiter, or 0.013 to 0.08 the mass of the sun. That puts them right between the most massive planets and the smallest stars.
TOI-201 c is on a highly elliptical orbit, taking 2,881 days to orbit its star, which has resulted in planets including a super-Earth named TOI-201 d and a warm Jupiter named TOI-201 b, forming in a narrow zone within its orbit, something that isn't just new to astronomers; it is completely unexpected based on planetary formation models.
The 5.8-day orbit of TOI-201 d and the 53-day orbit of TOI-201 b are both perfectly aligned with the orbit of the brown dwarf. The brown dwarf creates gravitational instability at distances equivalent to the distance between Mars and the sun, but this didn't prevent planets from forming in the system.
"This discovery provides a crucial insight into how planets form even around massive, eccentric objects," team member and INAF researcher Aldo Bonomo said in an emailed statement.
The system challenges the idea that gas giant planets form at distances equivalent to 2 to 3 times the distance between Earth and the sun in the disks of gas and dust that surround stars during their infancy.
"The presence of the brown dwarf on such an elliptical orbit forced the planets to form and survive by occupying the innermost and hottest edges of the primordial disk," team member Luca Naponiello of the National Institute for Astrophysics (INAF) said in the statement. "Furthermore, the data show that during the close approach of the brown dwarf, the warm Jupiter undergoes strong and sudden variations in its transit timing, bearing witness to an intense and vigorous dynamic interaction currently underway between the two giants."
The system was discovered by TESS using a rare mono-transit event, which describes a planetary body making one crossing of the face of its star, causing a dip in starlight. This was followed by an observing campaign conducted from the ground.
It is extremely rare to discover objects like TOI-201 c with such long and eccentric orbital periods using transits they make of their parent star. This brown dwarf is the first one of these objects to have its mass confirmed, making it an important step forward in astronomy.
"It [TOI-201c] is the transiting object with the longest orbital period for which the mass is known," Naponiello said.
The team's results were published on Wednesday (June 17) in the journal Nature.
This Magenta world's strange atmosphere made no sense until JWST found intriguing clouds made of salt.
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