This Magenta world's strange atmosphere made no sense until JWST found intriguing clouds made of salt.

An extreme exoplanet gives astronomers a rare look at weather changing in real time.

Who ordered the roasted exoplanet? Astronomers using the James Webb Space Telescope found a world that really puts the "hot" in "Hot Jupiter."

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

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.

Image: Artist’s concept exoplanet HD 80606 b

“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:

science.nasa.gov/webb

Downloads & Related Information

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.

Related 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

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.

Image: Artist’s concept exoplanet HD 80606 b

“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:

science.nasa.gov/webb

Downloads & Related Information

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.

Related 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

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.

"With its unprecedented observational quality, JWST gives us the most detailed glimpses into distant planets to date."

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 [...]

"We were totally amazed when we noticed this mass and size range of planet formation."

Eyes on Exoplanets Tutorial

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?

Transcript

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.

Our solar system may have hosted up to six giant planets in its first hundred million years, a new study suggests. The findings paint a more crowded picture of the early outer solar system than previously thought.

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.

Billions of Rocket-Powered Bumper Cars

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.

What we described just then is essentially solar radiation pressure plus the Yarkovsky effect. It turns out that the net force from this process typically averages out to zero as the ring particles orbit around the planet. This assumes, though, that the sunlight is constantly shining on the ring. Stunning imagery of Saturn tells us that this isn’t the case, so what happens when we take into account the shadow cast on the ring from the planet? Today’s authors find that the net effect induces a positive change in angular momentum of the ring particles, which they call the eclipse–Yarkovsky effect.

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.

Undeniably useful for Saturn, the eclipse–Yarkovsky effect may also explain some other conundra in the solar system. Mars may have once had rings, which are thought to have eventually clumped together to form the inner moon Phobos. This idea is problematic, though, in that current models suggest there should still be some residual ring system around Mars even after Phobos formed. Enter the eclipse–Yarkovsky effect: being 100 times stronger for Mars than Saturn (due to its more intense incident sunlight), the effect may have driven out and dispersed that residual ring altogether. While the authors are currently looking into this possibility, the reintroduction of the eclipse–Yarkovsky effect has already shown great promise for our most beautiful ringed planetary neighbour.

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.

It’s Snack Time

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.

Modeling Engulfment

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.

At the onset of the model, the engulfment is set to begin, the planet placed tangent to the star’s surface. The planets sink down and orbit just barely within their stars for 1–10 years, their solid surfaces slowly beginning to evaporate.

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.

Signs of Planets Past

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.

What this translates to, for the purposes of identifying planet-eating stars from afar, is that stars near the top of the mass range studied — from 1.0 to 1.4 solar masses — make the best targets. This is because the tell-tale planetary metals are not overly diluted within the stars’ relatively small convective zones, making these elements easier to detect. In terms of specific metals, the authors found that aluminum, calcium, and vanadium are the best signposts of planetary engulfment, with lithium also making the list.

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.

Citation

“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.

How to Probe a Planetary Atmosphere

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?

How Starspots Get in the Way

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.

Starspot Models: Our Solution?

To deal with this, astronomers build starspot models, where they vary the spots in terms of the following:

• The surface covering fraction: this parameter tells us how much of the stellar surface is covered in spots
• The temperature contrast: this parameter tells us how much cooler (in ratio) the spot is compared to the rest of the stellar surface, and by proxy how much dimmer

These models are promising, but how do we know that we have chosen the right parameters?

A Unique Laboratory: TOI-3884

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.

The planet transits the star, and as it does so, it always passes over the polar starspot. This gives us a rare opportunity to probe the spectrum of a starspot. Similar to how we can use normal in/out of transit observations to probe a planetary atmosphere, we can now compare the observations during/after a “starspot transit” to probe the starspot region. Today’s authors do exactly this using six different transit observations from JWST.

So… How Good Are Our Models?

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.

At wavelengths longer than about 1 micron, in the near-infrared regime, things look good! The residuals stay small, meaning the models do a solid job reproducing the observations. But move left into shorter wavelengths, in the optical regime, and the agreement quickly falls apart. The residuals grow, and it becomes clear that the models are missing something.

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.

There are many ways to observe the spectrum of a planet, but the one you’re probably most familiar with is transmission spectroscopy. You can learn more about transmission spectroscopy of exoplanet atmospheres and how to model transmission spectra with these bites: 1, 2, 3. However, all of the current techniques for exoplanet spectroscopy (including transmission spectroscopy) measure the star’s light and how the planet affects the star’s light. This means it’s heavily dependent on how we model the star’s light to indirectly observe the planet’s light. The only way to take the spectrum of a planet directly is with direct imaging: the technique that the future Habitable Worlds Observatory will use to find signs of life in planetary spectra.

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!

Snapshots

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.

The authors then run retrieval models on all nine spectra to see if the vegetation red edge would be detectable in each spectrum, including the time-averaged one. Retrieval models take into account characteristics of the planet that would affect how light moves through its atmosphere, such as the atmospheric chemicals present and the surface gravity. They then use this information to generate possible spectral models that could fit the data. The best-fit model allows astronomers to infer what the atmosphere is made of and properties of the planet such as surface gravity. Because we are looking at Earth in visible light, much of the light from the planet is reflected. Typically, models of Earth-like planets in visible wavelengths only include atmospheric albedo: the measure of how reflective a planet’s atmosphere is. However, surface biosignatures can also be reflective as shown by the vegetation red edge. The authors use this to their advantage and introduce a surface albedo into their model that changes with the amount of desert, vegetation, and ocean visible on Earth’s surface at that time. They then further divide the nine spectra into three different types based upon the visible surface: majority land; 50% land, 50% ocean; and majority ocean. Check out the article online to see a cool animation of the Earth rotating and how the spectrum looks different at each time!

Arr! There Be… Vegetables?

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.

For the first time (to the author’s knowledge), the vegetation red edge has been shown to be a promising and observable biosignature in Earth-like atmospheres. This study has also laid the groundwork for future work on other surface biosignatures and their potential impact on spectra of habitable planets. Confirming signs of life in multiple different ways, both on the surface and in the atmosphere, will finally allow astronomers to say we are not alone in the universe. In fact, life likes to live on the (red) edge!

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.

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