On June 17, in the year 2 B.C.E, a significant planetary conjunction occurred involving Venus and Jupiter. From Earth’s perspective, these two bright planets appeared to draw so close that they would have seemed to merge into nearly a single, brilliant object in the sky. This type of celestial alignment occurs because planets move inContinue reading "June 17, 2 BCE: A conjunction between Venus and Jupiter"
The post June 17, 2 BCE: A conjunction between Venus and Jupiter appeared first on Astronomy Magazine.
For nearly a decade, the hot Jupiter CoRoT-2 b has presented a profound mystery to astronomers: its atmospheric hot spot is inexplicably located opposite the position observed on all other exoplanets of its kind. This peculiar phenomenon challenges conventional wisdom about the nature of hot Jupiters and their atmospheric dynamics. Recent research led by Aurora Kesseli, a staff scientist at the NASA Exoplanet Science Institute (NExScI) housed within Caltech’s IPAC center, has shed new light on this enigma by leveraging advanced spectroscopic data obtained from the Very Large Telescope (VLT) at the European Southern Observatory. This breakthrough offers compelling evidence that CoRoT-2 b defies a fundamental assumption about hot Jupiters: it is not tidally locked to its host star.
Hot Jupiters are a fascinating class of exoplanets typified by their colossal size—often comparable to or exceeding that of Jupiter—and their blisteringly close orbits around host stars, sometimes completing a single revolution in mere days. Because of these properties, hot Jupiters serve as prime candidates for detailed atmospheric studies. Their proximity to the parent star means they receive intense irradiation, significantly influencing their atmospheric dynamics, radiative properties, and chemical compositions. This environment makes them critical laboratories for testing and refining planetary formation, evolution, and climate models.
The accepted paradigm for hot Jupiter atmospheres is predicated on tidal locking, whereby the planet’s rotation period synchronizes with its orbit, causing one hemisphere to perpetually face the star, exposed to relentless stellar radiation, while the opposite side remains cloaked in darkness. This lock is thought to occur rapidly due to strong gravitational interactions between the planet and its star. The perpetual dayside is expected to feature a dominant hot spot slightly offset towards the direction of planetary rotation and orbital motion, driven by atmospheric super-rotation. This consistent pattern is observed across many studied hot Jupiters, reinforcing tidal locking as a foundational concept within exoplanetary atmospheric science.
However, CoRoT-2 b stands out starkly against this backdrop. Discovered in 2007 and studied extensively since, this hot Jupiter’s hottest atmospheric region is displaced not ahead of but behind the substellar point—the point on the planet directly facing its star—opposite to the behavior seen in counterparts. Initial hypotheses proposed to explain this anomaly included obscuring cloud layers, magnetic field-driven atmospheric dynamics complicating wind patterns, or a rotation period differing from the orbital period. Previous work by Lisa Dang, a collaborator and professor at the University of Waterloo, outlined these potential explanations based on early observational data.
Aurora Kesseli and her team recently applied phase-resolved emission spectroscopy using the CRIRES+ instrument on the VLT, capturing the planet’s atmosphere in unprecedented detail across different orbital phases. This method enables tracing variations in emitted light corresponding to temperature and wind structures dynamically as the planet orbits. The data conclusively pointed toward the third hypothesis: CoRoT-2 b exhibits a rotation rate slower than its orbital period, meaning it is not synchronized tidally. Specifically, one full rotation of CoRoT-2 b lasts approximately three Earth days, while its orbital period is about 1.5 days. This differential implies that by the time the planet completes a single axial spin, it has circumnavigated its host star twice.
This non-synchronous rotation leads to a decoupling of the traditional tidally locked pattern of day-night heating contrasts, fundamentally altering how atmospheric circulation redistributes energy. Without tidal locking, the expected eastward-shifted hot spot is replaced by a distinct thermal signature resulting from slower planetary spin interacting with intense stellar irradiation. The discovery challenges standard assumptions embedded in many exoplanet climate models that universally prescribe tidal locking for hot Jupiters, suggesting a more nuanced picture with rotational diversity.
Understanding the rotational state of exoplanets like CoRoT-2 b carries broader implications, especially in the context of habitability studies. Many terrestrial exoplanets orbit M dwarfs, cool stars constituting roughly 70% of the stellar population in the Milky Way. These stars have habitable zones—regions where liquid water can persist on planetary surfaces—so close that tidal locking is highly probable within relatively short stellar lifetimes. Since rotation influences temperature gradients, weather systems, and atmospheric retention, a tidally locked terrestrial exoplanet’s climate could differ drastically from one with asynchronous rotation. Hence, unraveling CoRoT-2 b’s rotation contributes to refining the models employed for predicting environments on potentially habitable worlds in tight orbits.
While the revelation of CoRoT-2 b’s slow rotation solves a significant piece of the puzzle, it simultaneously opens further questions. The mechanisms driving this atypical rotational state in a planet where tidal forces should dominate remain elusive. Possible contributors might include magnetic torques, differential interior structures, or recent dynamical interactions within its planetary system that disturbed its spin. Future observations, especially with upcoming flagship observatories like the James Webb Space Telescope, the Habitable Worlds Observatory, and the ground-based Extremely Large Telescope, promise to provide deeper insight into these processes by offering higher precision data across broader wavelength ranges.
Hot Jupiters continue to act as vanguards in exoplanetary science. They are currently the best-understood and most accessible class of exoplanets for atmospheric characterization, enabling astronomers to test and recalibrate models of atmospheric physics, chemistry, and dynamics. The case of CoRoT-2 b exemplifies how nature’s variability often defies simplified expectations, compelling constant refinement of theories and models. These advances do not merely enhance comprehension of gas giants but ripple outward to shape understanding of all planetary atmospheres, including those bearing life.
Kesseli underscores the excitement of probing “weird” exceptions within the exoplanet census, emphasizing that such outliers drive scientific progress. As instrumentation improves and more extensive surveys unfold, the taxonomy of exoplanetary rotation states, atmospheric dynamics, and climate regimes will grow richer. This improved framework will essentialize our broader quest to understand planet formation, stellar influences, and potential biosignatures on distant worlds. CoRoT-2 b’s defiance of tidal locking invites the scientific community to remain alert to unexpected phenomena lurking in exoplanet atmospheres.
In summation, the unraveling of CoRoT-2 b’s anomalous atmospheric hot spot through rigorous spectroscopic measurements marks a milestone in exoplanet research. It dispels the notion of universal tidal locking among hot Jupiters and reveals a more intricate rotational behavior impacting atmospheric properties. The ongoing inquiry into the cause of this slowed rotation will propel future efforts to decipher planetary spins, magnetic interactions, and orbital dynamics across a diverse planetary population. These insights will deepen our grasp of planetary physics and help guide the search for habitable environments beyond our solar system.
Subject of Research: Atmospheric dynamics and rotational state of the hot Jupiter CoRoT-2 b
Article Title: Unraveling the Mystery of the Peculiar and Young Hot Jupiter CoRoT-2b II: Phase Resolved Emission Spectroscopy with VLT/CRIRES+ and Gemini-S/IGRINS
News Publication Date: June 16, 2026
Web References: IPAC News, NExScI at Caltech, University of Waterloo Newsroom
References: Kesseli et al., submitted to The Astronomical Journal
Image Credits: Keith Miller (Caltech/IPAC – SELab)
Keywords: hot Jupiter, CoRoT-2 b, tidal locking, exoplanet atmospheres, phase-resolved spectroscopy, planetary rotation, atmospheric dynamics, VLT/CRIRES+, exoplanet climate models, M dwarf habitability, rotational decoupling, spectroscopic observations
4 min read
One well-done gas giant, coming right up! That’s the latest from researchers analyzing NASA’s James Webb Space Telescope’s observations of HD 80606 b, an exoplanet four times the mass of Jupiter with an extremely elliptical orbit that sweeps close by its Sun-like star. The research team is presenting their study and preliminary findings Tuesday at the 248th meeting of the American Astronomical Society in Pasadena, California.
“Hot Jupiters are already considered some of the most extreme exoplanets we know of, but even among that population, HD 80606 b is one of the most extreme,” said Tiffany Kataria, the study’s principal investigator at NASA’s Jet Propulsion Laboratory in Southern California. “We typically think of hot Jupiters as hot gas giants sitting right next to their stars, but this planet’s highly eccentric orbit creates a completely different beast.”
As the planet plunges close to its star, Webb shows its temperature skyrockets by 1,100 degrees Fahrenheit. Previous studies have shown that radical temperature swings can cause an exoplanet’s chemistry and clouds to change in real time. According to the research team, the dynamic conditions of HD 80606 b make the planet an ideal target to observe these changes with Webb’s powerful instruments.
“Observing a planet like HD 80606 b is actually very efficient because its unusual orbit, with the corresponding swings in temperature and chemical composition, allow us to gather data under varying conditions in just hours and apply those findings to other hot Jupiters or more conventional exoplanets,” said Laura C. Mayorga, co-investigator on the study and an exoplanet astronomer at the Johns Hopkins Applied Physics Laboratory in Laurel, Maryland.
Measurements of temperature and chemical composition were done with spectroscopy, a technique scientists use to break light into its component colors to reveal information about the composition, temperature, motion, and physical properties of objects in space. The team used Webb’s MIRI (Mid-Infrared Instrument) for an extended observation of HD 80606 b before, during, and after its periastron, or closest pass by its star. During periastron, the planet also passed behind the star from Webb’s perspective in what’s known as a secondary eclipse. The observation was years in the planning, as scheduling the time to catch the planet at this point was complex given its extremely elliptical 111-day orbit, and Webb’s own restrictions on where it can look during specific times of the year, based on Earth’s position in orbit around the Sun.
Researchers say they have only begun to peel back the layers of an incredibly rich dataset, but they can clearly see a dramatic shift in the exoplanet’s temperature. “Webb has shown that the planet’s increase in temperature was even more extreme than we anticipated based on Spitzer data,” said Kataria.
In fact, the planet had already been dubbed the “roasted exoplanet” and even got its own poster in NASA’s popular series. NASA’s now-retired Spitzer Space Telescope laid the groundwork of infrared observations of HD 80606 b, showing that more detailed spectroscopic data from Webb would be especially compelling.
“Spitzer did amazing work on this exoplanet, and now Webb is building on that legacy by enabling us to drill down to distinguish specific chemical signatures like methane and carbon dioxide, which is just amazing progress,” said Ryan Challener, co-author and research associate at the Cornell Center for Astrophysics and Planetary Science. “There’s so much to learn from this one dataset here — we really are just getting started deciphering what Webb has to tell us.”
The James Webb Space Telescope is the world’s premier space science observatory. Webb is solving mysteries in our solar system, looking beyond to distant worlds around other stars, and probing the mysterious structures and origins of our universe and our place in it. Webb is an international program led by NASA with its partners, ESA (European Space Agency) and CSA (Canadian Space Agency).
For more information on Webb, visit:
The following sections contain links to download this article’s images and videos in all available resolutions followed by related information links, media contacts, and if available, research paper and Spanish translation links.
Este Artículo en Español – “Telescopio Webb de la NASA Detecta un Exoplaneto Asandose”
Read: Webb’s Impact on Exoplanet Research
Watch: How to Study Exoplanets: Webb and Challenges
Explore: Eyes on Exoplanets
Print: The Roasted Exoplanet Poster
More Webb: News | Images | Science | Home Page
Laura Betz
NASA’s Goddard Space Flight Center
Greenbelt, Maryland
laura.e.betz@nasa.gov
Leah Ramsay
Space Telescope Science Institute
Baltimore, Maryland
Hannah Braun
Space Telescope Science Institute
Baltimore, Maryland
4 min read
One well-done gas giant, coming right up! That’s the latest from researchers analyzing NASA’s James Webb Space Telescope’s observations of HD 80606 b, an exoplanet four times the mass of Jupiter with an extremely elliptical orbit that sweeps close by its Sun-like star. The research team is presenting their study and preliminary findings Tuesday at the 248th meeting of the American Astronomical Society in Pasadena, California.
“Hot Jupiters are already considered some of the most extreme exoplanets we know of, but even among that population, HD 80606 b is one of the most extreme,” said Tiffany Kataria, the study’s principal investigator at NASA’s Jet Propulsion Laboratory in Southern California. “We typically think of hot Jupiters as hot gas giants sitting right next to their stars, but this planet’s highly eccentric orbit creates a completely different beast.”
As the planet plunges close to its star, Webb shows its temperature skyrockets by 1,100 degrees Fahrenheit. Previous studies have shown that radical temperature swings can cause an exoplanet’s chemistry and clouds to change in real time. According to the research team, the dynamic conditions of HD 80606 b make the planet an ideal target to observe these changes with Webb’s powerful instruments.
“Observing a planet like HD 80606 b is actually very efficient because its unusual orbit, with the corresponding swings in temperature and chemical composition, allow us to gather data under varying conditions in just hours and apply those findings to other hot Jupiters or more conventional exoplanets,” said Laura C. Mayorga, co-investigator on the study and an exoplanet astronomer at the Johns Hopkins Applied Physics Laboratory in Laurel, Maryland.
Measurements of temperature and chemical composition were done with spectroscopy, a technique scientists use to break light into its component colors to reveal information about the composition, temperature, motion, and physical properties of objects in space. The team used Webb’s MIRI (Mid-Infrared Instrument) for an extended observation of HD 80606 b before, during, and after its periastron, or closest pass by its star. During periastron, the planet also passed behind the star from Webb’s perspective in what’s known as a secondary eclipse. The observation was years in the planning, as scheduling the time to catch the planet at this point was complex given its extremely elliptical 111-day orbit, and Webb’s own restrictions on where it can look during specific times of the year, based on Earth’s position in orbit around the Sun.
Researchers say they have only begun to peel back the layers of an incredibly rich dataset, but they can clearly see a dramatic shift in the exoplanet’s temperature. “Webb has shown that the planet’s increase in temperature was even more extreme than we anticipated based on Spitzer data,” said Kataria.
In fact, the planet had already been dubbed the “roasted exoplanet” and even got its own poster in NASA’s popular series. NASA’s now-retired Spitzer Space Telescope laid the groundwork of infrared observations of HD 80606 b, showing that more detailed spectroscopic data from Webb would be especially compelling.
“Spitzer did amazing work on this exoplanet, and now Webb is building on that legacy by enabling us to drill down to distinguish specific chemical signatures like methane and carbon dioxide, which is just amazing progress,” said Ryan Challener, co-author and research associate at the Cornell Center for Astrophysics and Planetary Science. “There’s so much to learn from this one dataset here — we really are just getting started deciphering what Webb has to tell us.”
The James Webb Space Telescope is the world’s premier space science observatory. Webb is solving mysteries in our solar system, looking beyond to distant worlds around other stars, and probing the mysterious structures and origins of our universe and our place in it. Webb is an international program led by NASA with its partners, ESA (European Space Agency) and CSA (Canadian Space Agency).
For more information on Webb, visit:
The following sections contain links to download this article’s images and videos in all available resolutions followed by related information links, media contacts, and if available, research paper and Spanish translation links.
Este Artículo en Español – “Telescopio Webb de la NASA Detecta un Exoplaneto Asandose”
Read: Webb’s Impact on Exoplanet Research
Watch: How to Study Exoplanets: Webb and Challenges
Explore: Eyes on Exoplanets
Print: The Roasted Exoplanet Poster
More Webb: News | Images | Science | Home Page
Laura Betz
NASA’s Goddard Space Flight Center
Greenbelt, Maryland
laura.e.betz@nasa.gov
Leah Ramsay
Space Telescope Science Institute
Baltimore, Maryland
Hannah Braun
Space Telescope Science Institute
Baltimore, Maryland
The post NASA’s Webb Catches Exoplanet Getting Roasted appeared first on NASA Science.
A team of astronomers has found strong evidence that a star similar to our sun may have eaten one of its own planets. The star, known as TOI-5882, is located about 1,300 light-years from Earth. Researchers discovered that it contains an unusually high amount of lithium, a chemical element that may reveal a dramatic event […]
The post Astronomers discover Sun-like star that likely swallowed one of its planets appeared first on Knowridge Science Report.
The hunt for Planet Nine continues as new discoveries make the Solar System’s biggest mystery even harder to solve. Is there a massive undiscovered planet on the outer reaches of the Solar System? The idea has been around since before the discovery of Pluto in the 1930s. Labeled as planet X, prominent astronomers had put [...]
Welcome to NASA’s Eyes on Exoplanets! Use this tutorial to start exploring worlds beyond our own. With this 3D interactive tool, you can visit all the stars beyond the Sun where we’ve found other planets, called exoplanets.
Choose a star or exoplanet and see an artist’s concept of what it might look like. Spin it around to see its sun and planetary system. Learn how long a trip there from Earth would take at light speed — or by jet plane, or family car!
Study the real versions of planets and stars cited in your favorite science fiction. See which planets reside in habitable zones, where liquid water could exist on their surfaces. Or, search “Where We Explore,” stars that future space telescopes will target when looking for Earth-like planets. You can also choose your location on Earth and see what’s in the sky above you right now.
Select any of the stars shown to see how many planets have already been found there. Examine how those star systems compare to the layout of our solar system, or check the sizes of individual planets — are they as small as Earth, or as big as Jupiter?
See all the different techniques we’ve used to confirm the 6,000+ exoplanets discovered so far — among the billions we believe exist in the galaxy — and the many observatories, on Earth and in space, that have detected them. You can also browse some of our favorite weird worlds, or destinations featured in our Exoplanet Travel Bureau.
Where will you explore?
Welcome to NASA’s Eyes on Exoplanets. With this interactive tool, you can explore all of the stars beyond the Sun where we’ve discovered planets known as exoplanets. When you enter the site, the default is this view from space. You can start your exploration here. Or if you know of a specific star or exoplanet you want to visit, enter that in the search bar at upper right.
You can also select View from Earth. Choose your location and see what’s in the sky above you right now. Click and drag to explore different parts of the sky. In the lower right corner, you can choose different display options. You can see the constellations, view only stars that are visible to the naked eye, or see the stars that are good places for future telescopes to search for planets like Earth.
These future target stars are shown as filled-in circles. If you click the gear symbol and switch from the star symbol to the circled number, you will see how many exoplanets have already been found around the star shown.
When you select a star, you have three different view options. Starting in System View, you will see the star and where planets are located around it. The shaded green area marks the habitable zone, the region around a star where a planet could have liquid water on the surface, a key to the search for life beyond Earth. You can also see how this system compares to our solar system by selecting that feature in the lower right. The star view will show a hypothetical view of what the star might look like.
Click “Learn More” to see basic information about the star, including its history and pop-culture references. You can see how it compares to our Sun and solar system and what we found so far. Under “How to Detect a Planet in the System,” you can learn about the different ways to discover an exoplanet and see how many planets have been found with each technique, as well as the prospects for discovering more. Finally, the planet view allows you to explore each planet in the system.
For each confirmed exoplanet, you’ll see an artist’s concept of what it might look like and see how it compares to other planets. Planets also have an option to learn more, where you can see how far away it is, how long it would take to get there, how it was discovered, and which observatory found it.
To see other discoveries made by that observatory, click “Browse Destinations” in the upper right menu. There you can also find curated lists of featured discoveries and truly weird worlds.
As you can see, there are so many worlds to discover. Where will you explore?
The post Eyes on Exoplanets Tutorial appeared first on NASA Science.
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: Dynamics of Planetary Rings Under Thermal Forces
Authors: Wen-Han Zhou et al.
First Author’s Institution: The University of Tokyo
Status: Published in ApJL
If you ask anyone what their favourite planet is, the answer you’ll most likely hear is Saturn. Why? Why else than the beautiful and intricate ring system surrounding the gas giant. The other gas and ice giants in our solar system — Jupiter, Uranus, and Neptune — have ring systems themselves but none quite as striking as Saturn’s. Would it surprise you to learn that astronomers’ best models have not yet totally explained why Saturn’s rings look the way they do?
In contrast, it may not surprise you to hear that people have been trying to explain the rings for as long as we have seen them with telescopes. We now know that planetary rings are collections of relatively small particles (think micrometre up to metre sized), most likely having once been the material of a larger body that was disrupted either by collisions or tidal forces. This material, due to the gravity of its local planet, is sculpted into a flat disc where more subtle interactions then lead to substructure forming within the disc such as gaps and ringlets. Many of these substructures are explained by well-understood physics — for example gaps being carved by embedded moonlets or resonances sculpting ring edges — though there remain some outstanding problems in our understanding.
The authors of today’s article set their sights on the problematic inner edge of Saturn’s A ring (Figure 1). They describe some mechanisms — namely the collisions of micrometeoroids within the rings — by which a sharp ring edge can be maintained, but there exists a gap in the understanding of how such an edge can form in the first place. All hope is not lost, though, as today’s authors reintroduce a physical process they call the “eclipse–Yarkovsky” effect, which seems to explain these phenomena.
Figure 1: A horizontally sliced image of Saturn’s rings shows the rich substructure and gaps within the various rings. Saturn, which is not shown here, would be to the left of the image. The authors of today’s article are particularly concerned with the bright and sharp inner (left side) edges of the A and B rings. Click to enlarge. [NASA/JPL/Space Science Institute]
The idea behind this process revolves entirely around light. When sunlight hits a particle within a planetary ring, non-absorbed sunlight imparts a little “bump” onto a particle, ever so slightly altering its trajectory. At the same time, some of the sunlight is absorbed into the particle, which heats it up; light is soon re-emitted via thermal radiation, which, again, can slightly change the trajectory of these tiny particles. From a point on the surface of each ring particle (see rightmost side of Figure 2), the photons from this thermal radiation are all emitted in random directions; however, across the whole surface of the particle there is a net force! These tiny particles are spinning, and so the side just near “sunset” is hottest and emitting the most thermal photons. In this way, the pressure from the sunlight plus the thermal radiation of each particle imparts a net torque on the ring itself which changes the angular momentum of the ring.
Figure 2: Starlight is the main source of light onto the particles that make up a planetary ring (right panel) though reflected light from the planet’s surface hits it too. This light “heats up” the ring and forms an asymmetry as the ring is eclipsed by the planet, which produces a net force. [Zhou et al. 2026]
After today’s authors detailed all of the math involved in this process (and there is a lot), they put it into practice to try to help explain Saturn’s curious rings. Including the eclipse–Yarkovsky effect together with other known effects that drive ring evolution allowed them to reproduce the optical depth profile (how thick the ring looks) of Saturn’s A ring better than ever before (notably the sharp inner edge in Figure 3). On top of this, the effect provides another avenue for moonlet formation in the outer edges of ring systems as the positive torque from the effect drives material out toward and away from the Roche limit.
Figure 3: The authors try to explain the current structure of Saturn’s A ring by initialising it with a Gaussian profile of optical thickness versus radius (black dot-dashed line) and evolving it for 81 million years under different effects. When viscous effects are included (blue dashed line), the ring spreads out, but it’s only when the eclipse–Yarkovsky (EY) effect is included (red line) that the model closely matches the observed data (grey line). [Zhou et al. 2026]
Original astrobite edited by Wasi Naqvi.
About the author, Ryan White:
I am a first-year PhD student at Macquarie University in Australia, working mainly on binary/multiple systems with massive stars (Wolf–Rayets in particular!). Outside of study, I’m probably drinking coffee, baking, reading, or going for a run. You can also find me procrastinating on Bluesky @astroryan.bsky.social.
The post Shining a Light on the Shadowy Movements in Saturn’s Rings appeared first on AAS Nova.
Giovanni Cassini was born in Perinaldo, in what is now Italy, on June 8, 1625. Early work on Jupiter and Mars’ rotational periods and the positions of Jupiter’s satellites led to an invitation to Paris and the Academie des Sciences by King Louis XIV; he became director of the Observatorie de Paris in 1671, andContinue reading "June 8, 1625: The birth of Giovanni Cassini"
The post June 8, 1625: The birth of Giovanni Cassini appeared first on Astronomy Magazine.
Planets that get too close to their host stars are liable to be engulfed and consumed. New research explores how to identify stars that have had a planetary snack.
Being a planet that closely orbits its star is dangerous, and various dynamical processes can draw a planet inward past the point of no return. When a planet vanishes beneath the surface of its host, it eventually disintegrates within the star, its atoms mixing into the blazing stellar soup.
This outcome is likely extremely common across the universe, and researchers have begun to see evidence for it: stars that appear to have absorbed angular momentum from their planets, white dwarfs with uncanny metals in their spectra, and stars with chemical abundances that don’t match those of their siblings. Now, in a recent publication led by Kaitlyn Lane (Vanderbilt University), researchers seek to find observational signatures of planetary engulfment of rocky exoplanets by main-sequence stars.
Lane’s team focused on main-sequence stars in the range of 0.5 to 1.4 solar masses, using one-dimensional analytical models to determine which of these stars will most readily display signs of having engulfed a planet. They simulated the stars as they consumed either an Earth-like planet or a super-Earth with the same composition as Earth but 15 times its mass.
Diagram showing a planet being engulfed by its star and beginning to disintegrate before migrating inward. The boundary between the star’s outer convective zone (CZ) and inner radiative zone is shown. Click to enlarge. [Lane et al. 2026]
After that relatively lengthy phase, the process proceeds rapidly: as the planet inches deeper into its star, the drag forces grow stronger and the planet’s demise accelerates, with the planet disintegrating over the course of hours. In the last phase, the planet makes its final plunge and is destroyed in a half hour.
Lane’s team found that the planets tended to be destroyed fully within the outer convective layer of their stars, except in the case of the most massive stars studied here. For more massive stars, the outer convective zone is shallower than it is for the less massive stars, allowing a chunk of each planet to survive the passage through the convective zone to reach the radiative zone below.
The trajectories of three example cases, showing how the planet loses mass as it spirals inward. In the 1.4-solar-mass case, part of the planet survives to reach the radiative zone, but the shallowness of the star’s convective zone means that the disintegrated planetary material is easier to observe. Click to enlarge. [Lane et al. 2026]
While the authors acknowledge that there’s more work to be done — they plan to investigate the impacts of planetary engulfment on stellar structure more closely, for example — this work represents an important foray into identifying targets for future studies of stars that have eaten their planets.
“Observable Metal Pollution in Main-Sequence Stars: Simulations of Rocky Planets Engulfed by Stars in the 0.5 to 1.4 M⊙ Range,” Kaitlyn T. Lane et al 2026 ApJ 1003 67. doi:10.3847/1538-4357/ae5b9a
The post Now That’s Metal: How to Spot Stars That Have Swallowed Their Planets appeared first on AAS Nova.
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: A Panchromatic JWST Spectrum of a Giant Starspot on the Fully Convective M Dwarf TOI-3884
Authors: C. A. Murray et al.
First Author’s Institution: University of Colorado Boulder
Status: Published in ApJ
We often picture stars as smooth, glowing spheres, as if they’ve been run through an Instagram filter. But real stars have spots: cooler, darker regions on a star’s surface caused by strong magnetic fields.
Annoyingly, these spots can seriously interfere with how we study exoplanet atmospheres.
Planetary atmospheres are often probed through transmission spectroscopy. When a planet transits its star, some starlight passes through the planet’s atmosphere before reaching us. We can distinguish the light that has passed through the planet’s atmosphere by comparing the star’s light in transit versus out of transit. In doing so, we can isolate the atmospheric spectrum and look for absorption features of species like water or oxygen.
Easy, right?
Things get more complicated once we stop thinking of the star as if it’s been smoothed out by an Instagram filter. Starspots are cooler than the surrounding stellar surface, which means they emit a different spectrum. They are also constantly changing: new spots can form, old ones can disappear, and the star’s rotation carries them in and out of view. This changes things.
First of all, your star’s spectrum changes over time, which could mean that the star’s spectrum out of transit is not the same as the star’s spectrum during transit. On the other hand, the planet may transit across a starspot instead of a “normal” stellar region. In this case, the light we measure during the transit is affected by the spot, and it is no longer accurate to directly compare it with the overall stellar light outside the transit.
Ultimately, absorption features that we thought were from the planetary atmosphere could actually be coming from starspot contamination instead.
To deal with this, astronomers build starspot models, where they vary the spots in terms of the following:
These models are promising, but how do we know that we have chosen the right parameters?
The TOI-3884 system is a unique laboratory for testing our starspot models. As seen in Figure 1, it has very convenient starspot geometry, with a large starspot located close to its pole. On top of that, we observe this star almost completely pole-on, which means that we always see this starspot, no matter how much the star rotates. To top this all off, the star hosts a close-in planet, which orbits the star from pole to pole.
Figure 1: Illustration of the TOI-3884 system. The pole (and rotation axis) of the star is indicated with a black “x,” indicating that we see the star almost pole-on. The polar starspot is indicated in grey, and the transiting planet TOI-3884b is indicated in black. Different dates are shown, illustrating how the system evolves over the span of a few weeks. [Adapted from Mori et al. 2025]
From the JWST observations, the authors extract a starspot spectrum for the first time. Figure 2 shows this as the spot contrast (how much dimmer the spot is than the surrounding stellar surface) plotted across different wavelengths. To see how well our models are doing, they compare this observed spectrum to two commonly used starspot models. The difference between the data and the models (the residual) is plotted in the lower panel.
Figure 2: The spectrum of TOI-3884’s starspot. The y-axis in the upper panel, the spot contrast, indicates how much dimmer the starspot is compared to the “normal” stellar surface. Different observations taken with JWST are indicated in different colored crosses, and other previous observations are overplotted in various other shapes. Model starspot spectra are shown in dashed or dotted black lines. The residuals between the model spectra and the JWST observations are shown in the bottom panel. [Adapted from Murray et al. 2026]
There’s still work to be done before we can confidently probe planetary atmospheres at optical wavelengths without worrying about stellar contamination, and this observed starspot spectrum provides a unique benchmark to test future starspot models. For now, the near-infrared remains a safer and more reliable window for planet atmosphere studies.
Original astrobite edited by Natalie Price.
About the author, Elise Koo:
I’m a PhD student at the University of Amsterdam, working to detect magnetic interactions between stars and their planets using radio and spectroscopic observations. Outside of research, I like to try out a variety of sports.
The post The First Starspot Spectrum Revealed by JWST appeared first on AAS Nova.
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: Retrieving the Red Edge on Earth-Like Planets with Heterogeneous Clouds and Surfaces
Authors: Zachary Burr et al.
First Author’s Institution: Jet Propulsion Laboratory; ETH Zurich
Status: Published in ApJ
In the next 25 years, astronomers could find signs of life on other planets with the launch of the Habitable Worlds Observatory. Atmospheric signs of life, known as atmospheric biosignatures, are how astronomers currently search for life on other planets. Figure 1 shows examples of atmospheric biosignatures with pictures of each chemical’s origin on Earth. Before E.T. can phone home, though, we have to understand what chemicals make up a planet’s atmosphere. To do this, astronomers can use spectroscopy to observe a planet’s atmosphere in different wavelengths and measure the types and quantities of chemicals present.
Figure 1: Atmospheric biosignatures present in Earth’s atmosphere. More abundant biosignatures include oxygen and ozone (byproducts of photosynthesis in plants and bacteria) and nitrous oxide (byproduct of bacteria that don’t need oxygen to survive). Less abundant biosignatures include isoprene (released from the breakdown of leaves that have fallen from trees) and sulfur gases (byproducts of cyanobacteria). [Kaz Gary]
But are atmospheric biosignatures the only way to tell if life exists on other planets? Short answer: absolutely not. Let’s take Earth as an example. If we imagine Earth as a directly imaged exoplanet and take spectra of the light it reflects, you’ll find that around near-infrared wavelengths (~700 nanometers or just past the red part of the visible light spectrum), the light reflected off of Earth increases sharply. This sharp increase is called the vegetation red edge and is caused by plant and ocean life on Earth’s surface as shown in Figure 2. This is made possible because chlorophyll (the thing that makes plants green) absorbs nearly all visible light but reflects near-infrared light. The vegetation red edge is an example of a surface biosignature. In today’s article, the authors determine if the vegetation red edge will be visible in spectra of Earth-like exoplanets!
Figure 2: Spectra of different sources of the vegetation red edge on Earth. The vegetation red edge is highlighted in gray where the spectra rapidly increase and then level off beyond the visible light part of the spectrum. Each color represents a different source with pictures of each source on the right-hand side of the plot. [O’Malley-James and Kaltenegger 2019]
Planets rotate; that’s how we have morning, noon, and night in 24 hours guaranteed. This means that different parts of the surface will be visible at different times when we take spectra. Sometimes, we may see more ocean than land, other times not. To determine if the vegetation red edge would be visible at all points in Earth’s day, the authors simulated nine different spectra of modern-day Earth representing nine snapshots of Earth’s rotation. Additionally, they also simulated a time-averaged spectrum that shows an entire Earth day in one snapshot without the time variability. These spectra are shown in Figure 3.
Figure 3: Spectra of a directly imaged modern-day Earth at nine different times in its rotation. The y-axis is the ratio of the planet’s signal to the star’s signal and the x-axis is wavelength in microns. Each color represents a time in UTC and the black curve represents the time-averaged spectrum. [Burr et al. 2026]
After running the models, the authors were able to detect a sharp increase in the surface albedo value in every spectrum, including the time-averaged one. This result is shown in Figure 4. The authors take this result one step further in order to validate that the vegetation red edge is actually a result of surface variation of vegetation. They re-run models on each of their spectra but instead include a constant surface albedo instead of a time-varying one. This resulted in incorrectly measured radii, chemicals, and surface gravity in nearly all of the models. Without the vegetation red edge and surface features, the models could not accurately determine if life was present on Earth.
Figure 4: Retrieved surface albedos for the nine time-varying spectra. The surface albedo is broken down into three different values (a₁, a₂, a₃). Each of these values represents a change in the surface albedo at different wavelengths (i.e., how reflective the surface is at three different wavelengths). The nine spectra were broken down by the amount of surface that was visible at that time and color-coded for each category. The time-averaged spectrum is shown in gray. Each category of spectra was able to retrieve an increase in reflected light from the surface at vegetation red edge wavelengths. The spectra that had the majority land visible have the biggest increase in the surface albedo. This makes sense since the amount of visible vegetation is the largest with majority-land planets. [Burr et al. 2026]
Original astrobite edited by Madison VanWyngarden.
About the author, Kaz Gary:
I am a fourth-year PhD candidate at The Ohio State University with a passion for planets. My current work focuses on modeling exoplanet observations for the Habitable Worlds Observatory and understanding planetary atmospheres. Outside of research, I help develop planetarium shows and love all forms of science communication. In my free time, I enjoy playing tabletop RPGs, painting, watching terrible reality TV, and hanging out with my pet hedgehog.
The post Life on the (Red) Edge appeared first on AAS Nova.
Each Jupiter-size planet in the galaxy falls into one of three distinct categories: hot, warm, or cold. A new study suggests that despite the apparent differences between these populations, they may have all formed from the same underlying dynamical process: a game of pool played at planetary scales.
Though our solar system has only one Jupiter-size planet, elsewhere in the galaxy we have found three different species of these massive gas giants. Cold Jupiters closely resemble their namesake and orbit far from their host stars; hot Jupiters are the opposite and are found whipping around their stars on extremely close-in orbits. In between these are the warm Jupiters, which tend to orbit in the intermediate space between 0.1 and 1.0 au.
An artist’s depiction of a hot Jupiter. These planets orbit extremely close to their host stars, but likely got to their locations by scattering inward from more distant orbits. [NASA/JPL-Caltech]
Given these differences, it’s often thought that each of these populations arrived at its current location through different dynamical processes and that the history of the warm Jupiters is likely quite different from the history of the hot Jupiters. However, a new study led by Julia Esposito (Georgia Institute of Technology) has proposed an alternative view. Maybe these populations, though they appear different now, were all created by the same process: planet–planet scattering.
A schematic showing where different planets ended up as a function of where they scattered from during their evolution. Click to enlarge. [Esposito et al. 2026]
At the end of the simulation, the team surveyed the digital carnage. Almost every virtual system ended with only two planets after either ejecting one away from the star or having two planets collide. But, remarkably, the remaining two-planet systems looked tantalizingly similar to what we actually observe, with a mix of hot, warm, and cold Jupiters. Even more exciting, the end populations were highly correlated to where the violent scattering event took place.
For example, the warm Jupiters were almost all produced by “warm scattering” simulations, where the scattering took place between 0.1 and 1.0 au. The planets that survived the simulations and ended up as warm Jupiters matched all of the properties of the real warm Jupiter population: they had nearby companions, were moderately eccentric, and were mostly aligned with their stars. The hot Jupiters, meanwhile, were almost all produced by “cold scattering” events where the flybys happened far from the star and resulted in one planet hurtling inwards. These also matched all of the observed properties of real hot Jupiters.
The researchers concluded that planet–planet scattering can produce both the warm and hot Jupiter populations so long as you let the planets scatter from a variety of different distances. This exciting theoretical insight, if correct, would mean that astronomers could stop searching for different pathways to create each population. Happily, this model also provides testable predictions, and the authors lay out how the theory could be supported or disproven with additional data. Through virtual experiments like these, astronomers continue to build up an understanding of how the wide range of planetary architectures observed across the galaxy came to be.
“Unified Formation Channel of Hot and Warm Jupiters via Planet–Planet Scattering,” Julia Esposito et al 2026 ApJL 1003 L3. doi:10.3847/2041-8213/ae61b0
The post Playing Pool with Planets appeared first on AAS Nova.
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: A Deep Search for Exomoons Around WISE 0855 with JWST
Authors: Mikayla J. Wilson et al.
First Author’s Institution: University of California, Santa Cruz
Status: Published in AJ
The solar system hosts hundreds of moons, ranging from volcanic worlds like Io around Jupiter, to icy objects like Enceladus around Saturn, to captured objects like Neptune’s retrograde moon Triton. Moons are essential to our model of how the solar system formed and also offer some of the best chances we have for finding life beyond Earth.
Astronomers also expect exomoons, or moons orbiting planets outside the solar system, to be abundant around other giant exoplanets. But how common are exomoons? How do they compare to the moons in our solar system?
In order to begin answering those questions, we must first detect an exomoon, which has proved difficult despite decades of searching by astronomers. Fortunately, JWST presents a new opportunity to uncover the exomoon population by looking at lonely free-floating planets as they drift through space.
One proposed method for searching for exomoons is by looking for their transits in front of their host planets, characterized by the dips in brightness of the planet as the moon passes in front, blocking the planet’s light. Looking for exomoon transits around planets orbiting stars is quite difficult, as the bright starlight can easily drown out the small signals of exomoon transits. Free-floating planets solve this issue by removing the star entirely, increasing our sensitivity to such detections. (See this bite for a good review.)
The authors of today’s article directed the exomoon hunt towards the free-floating WISE J085510.83-071442.5 (or WISE 0855). It has the prestige of being the coldest known brown dwarf (250–285K) while also sitting at a relatively low mass (3–10 Jupiter masses). Notably, it is also one of our closest neighbors at a distance of only 7.4 light-years, making it ideal for high-precision observations despite its faintness. Even though brown dwarfs are technically distinct from planets, the authors opt to refer to companions around WISE 0855 as moons given WISE 0855’s “planetary-mass” status. (It’s complicated…)
The JWST observations used in this study contain 11 hours of near-infrared (2.87–5.27 microns) time-series spectra originally intended to study water clouds and weather on WISE 0855. Time-series brightness monitoring can also be used for transit searches, which the authors take advantage of.
One complication is that WISE 0855 is variable, meaning its intrinsic brightness changes over time. Variability is likely driven by clouds and other dynamic processes within its atmosphere. So how do the authors distinguish between a passing moon and a turbulent atmosphere? The key idea is that variability is wavelength dependent, meaning that the brightness of WISE 0855 will fluctuate differently depending on the observed wavelength. In contrast, transits are “gray,” meaning that the same amount of light is blocked at all wavelengths, producing a consistent feature across the entire spectrum.
The authors apply this idea and pick out two wavelength regions of WISE 0855’s spectrum that contain two distinct variability patterns, which should both contain an identical moon transit signal (if present). They then generate a light curve (how brightness changes over time) for these two regions (see Fig. 1).
Figure 1: (A) Light curves from two selected wavelength regions of WISE 0855’s spectrum with injected transit signals. Also plotted is the best-fit Gaussian processes + transit model for the two light curves. (B) Light curve data after subtracting the Gaussian processes portion of the best-fit model, revealing the example injected transit signals. [Wilson et al. 2025]
Using Bayesian evidence (a measure of how well each model explains the data), they determined which model was favored. So, what do they find?
Based on Bayesian evidence, the authors conclude that there are no statistically significant detections of exomoons in the data. The results suggest very weak evidence for a ~0.53-Earth-radius moon at a wide separation from WISE 0855 — an unlikely scenario given that transit probability decreases at greater separations (and therefore longer orbital periods).
Yet, the study goes further: What kinds of moons is JWST able to detect, if any? To answer this, the authors performed injection and recovery tests, where they injected artificial transit signals of varying depths (exomoon sizes) into the data and tested how well their models were able to recover them (results shown in Fig. 2). They find that JWST is capable of detecting 96% of transits with depths ≥0.5%, equivalent to a Titan-like moon. Smaller Io-like moons were also detectable more than half of the time. This means that if a Titan analog had actually transited during these observations, we would almost certainly have seen it!
Figure 2: Results showing the number of successful detections for the transit injection and recovery tests. Fifty transit injections are done for transit depths of 1%, 0.5%, 0.4%, 0.3%, 0.2%, and 0.1%. The transit depths represent different exomoon sizes, with the shaded regions representing Io-like and Titan-like moons. [Wilson et al. 2025]
Original astrobite edited by Kelsie Taylor.
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 Hunting for Exomoons Around a Lonely Planet appeared first on AAS Nova.
Orbiting a white dwarf, the exoplanet WD 0806b is the subject of a recent study using JWST to measure the atmospheric conditions governing the planet.
Most of the 6,000 and counting exoplanets discovered thus far have been detected due to their impacts on their host star — passing in front of the star and causing it to dim, or gravitationally tugging on the star and causing it to wobble. On rare occasions, though, astronomers have been able to catch the exoplanet itself through direct imaging. Directly imaged exoplanets offer key insights that cannot be obtained through indirect detection methods. Luminosity measurements and spectral emission features allow astronomers to more directly measure planet mass, radius, and composition otherwise inferred from the host star.
NIRCam image showing host star WD 0806 circled in orange and the location of exoplanet WD 0806b marked by the orange arrow. [Lew et al 2026]
Aiming to characterize the physical properties and atmospheric composition of WD 0806b, Ben W.P. Lew (Bay Area Environmental Research Institute; NASA Ames Research Center) and collaborators used JWST’s Near-Infrared Camera (NIRCam) and Near-Infrared Spectrograph (NIRSpec) to obtain high-resolution imaging and spectroscopy of the exoplanet. Combining these observations, prior lower-resolution observations, and evolutionary planet models, the authors estimated the physical properties of WD 0806b including mass, radius, surface gravity, and effective temperature.
NIRSpec spectrum of WD 0806b with best-fit model spectra overlaid. [Lew et al 2026]
This study highlights how high-precision JWST data can reveal a rich collection of atmospheric conditions, chemical composition, and physical processes occurring in cold giant planets. With such a wide orbit from its host white dwarf, WD 0806b serves as an interesting case study for how giant planet composition may reflect the formation and evolutionary history of the overall system. Future observations of and comparisons to similarly cold giant planets will further uncover how atmospheric characterization may fit into our understanding of exoplanets and their histories.
“JWST Spectral Retrieval of Cold Directly Imaged Planet WD 0806b and the First Measurement of Altitude-dependent Kzz in Exoplanet Atmospheres,” Ben W.P. Lew et al 2026 AJ 171 227. doi:10.3847/1538-3881/ae4747
The post Characterizing the Atmosphere of Exoplanet WD 0806b with JWST appeared first on AAS Nova.
After AAS 247 in Phoenix, Arizona, AAS Nova Editor Kerry Hensley and I had the chance to travel about 150 miles south for a tour of Kitt Peak National Observatory.
Located 60 miles southwest of Tucson, Kitt Peak National Observatory (KPNO) resides on a mountain top within the Tohono O’odham Nation reservation. Founded in 1958, Kitt Peak is home to nearly two dozen active telescopes ranging in wavelength coverage and scientific objectives. Ronald Proctor, Lori Allen, and Jacelle Ramon-Sauberan, all serving in crucial roles for the observatory, led our tour around the mountain.
The Windows On the Universe Center’s lobby exhibit displaying the Tohono O’odham language with words describing the land and astronomy. Jacelle Ramon-Sauberan, the Tohono O’odham Nation Education Liaison, is seen to the left. [KPNO/NOIRLab/NSF/AURA/R. Proctor; CC BY 4.0]
The center’s lobby introduced visitors to the beautiful land KPNO calls home. Working with Tohono O’odham linguists, Jacelle, the observatory’s Tohono O’odham Nation Education Liaison, curated the lobby exhibit that features the native language and the Nation’s connection to astronomy and the observatory. The science center serves as an educational resource and place of cultural exchange, expanding the relationship between the observatory and the Tohono O’odham Nation.
Apollo astronauts in the control room of the McMath-Pierce Solar Telescope in 1964. [United States Geological Survey; CC BY 4.0]
At the end of the Windows Center is a Science On a Sphere Theater — a spherical display system that allows visitors to see planets, stars, moons, and even large-scale structures of the universe in 3D. Featuring multiple programs, the theater takes visitors through the universe and displays data collected right there on the mountain!
The WIYN 3.5-meter telescope at sunset. [KPNO/NOIRLab/NSF/AURA/P. Marenfeld; CC BY 4.0]
Though not typically open to the public for tours, our next stop took us to the WIYN 3.5-meter telescope. This telescope is operated and owned by the WIYN Consortium, a partnership between the University of Wisconsin, Indiana University, NSF’s NOIRLab (National Optical-Infrared Astronomy Research Laboratory; formerly NOAO), Pennsylvania State University, and Princeton University. Operating since 1994 with a strong collection of instruments, WIYN has observed galaxies near and far, stars across their lifetimes, and exoplanets tugging on their host stars.
Me, Lexi Gault (AAS Media Fellow), in front of the WIYN 3.5-meter telescope. I have used WIYN’s SparsePak spectrograph to collect data for my dissertation research! [AAS Nova/Kerry Hensley]
The partnership between public and private universities and a government institution was the first of its kind. Through this consortium, hundreds of undergraduate and graduate students have conducted research with WIYN, and the telescope’s suite of instruments have enabled early career astronomers to explore the universe both near and far.
We concluded our tour at the Mayall 4-meter Telescope, the tallest telescope dome on the mountain at a staggering 18 stories high. This iconic telescope saw first light in 1973, and at the time, was the second-largest (in diameter) telescope in the world. Originally built for wide-field optical and infrared studies of the universe, the Mayall has enabled decades of critical scientific research.
The Mayall dome across the mountain as seen from inside the WIYN dome. [AAS Nova/Lexi Gault]
From the telescope’s massive dome, to the busy DESI control room, to the gallery floor with a nearly 360 degree view of the surrounding desert, the Mayall offers visitors a unique glimpse into Kitt Peak’s history and its future. While WIYN is a hidden gem, the Mayall 4-meter Telescope is open to the public for tours daily, so you can experience the exciting era of research and discovery at KPNO.
Interested in getting a peek yourself? KPNO is open to the public daily with multiple tour types to choose from, including both daytime and nighttime visits! Plan your visit to Kitt Peak here.
The post Getting a Peek of Kitt Peak National Observatory appeared first on AAS Nova.
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