At the 2025 Meeting of the American Astronomical Society, two pioneering teams of astronomers—one from Penn State and the other from MIT—revealed exciting new discoveries about an extreme and fascinating form of planetary destruction. These discoveries offer a closer look at the disintegration of rocky planets due to intense heat from their host stars, a phenomenon that provides researchers a rare chance to explore exoplanetary interiors in ways previously unimaginable. Through the combined efforts of the James Webb Space Telescope (JWST) and the Transiting Exoplanet Survey Satellite (TESS), scientists have been able to capture insights into planets that are essentially melting away under the blazing gaze of their stars.
The Role of Transiting Planets in Discovery
In both studies, astronomers made use of transits—the dimming of starlight caused when a planet passes directly in front of its star from the observer’s perspective. These transits provide crucial data on planets’ characteristics, as the light from the star filters through a planet’s atmosphere and, in the case of disintegrating planets, through the dusty material being cast off the planet’s surface. Most exoplanets have orbits that cause regular, symmetric transits. However, the two teams focused on an incredibly rare subclass of planets—Ultra-Short Period (USP) planets. USPs are characterized by their extremely rapid orbits, circling their parent stars in just a few hours. The proximity to their stars subjects them to intense radiation and heat, and in the case of disintegrating USPs, this heat is enough to cause their surfaces to evaporate into space.
This evaporation is not just an unremarkable side effect—it’s a dramatic, often violent process, observable via both thermal signatures and dusty tails trailing behind the planets as their material is blasted into space. The phenomenon of disintegrating planets, which are a rare subcategory of USPs, allows astronomers to study a planet’s composition by observing the material being lost during the process of destruction. With this, scientists have gained an unprecedented opportunity to investigate the makeup of rocky planets—similar to those like Earth, Venus, and Mars—outside of our own solar system.
The Penn State Discovery: K2-22b
The first major breakthrough came from the Penn State team, led by Nick Tusay, a Ph.D. student working at the Center for Exoplanets and Habitable Worlds. Using the James Webb Space Telescope (JWST), this team probed the exoplanet K2-22b, a disintegrating planet orbiting the star K2-22, discovered during NASA’s extended K2 mission with the Kepler Space Telescope. This planet’s rapid orbit—every 9.1 hours—and surface temperature of 2,100 K are sufficient to melt and vaporize iron and rocky materials. K2-22b’s extreme proximity to its star places it in a zone where intense heat causes its materials to evaporate, forming a dust cloud around the planet. This cloud is not symmetrical, as material escapes from the planet’s atmosphere in a chaotic, irregular pattern. As the planet moves in front of its star, the dust tail, much like a comet tail, becomes visible, adding additional complexity to the light-curve of the planet’s transit.
Tusay and his colleagues utilized JWST’s mid-infrared spectrograph (MIRI) to collect the planet’s spectrum before, during, and after the transit, effectively capturing data on the planet’s disintegrating material. What they found was a spectrum showing signatures consistent with silicate material—potentially from the planet’s mantle—confirming that K2-22b still retains some of its rocky material despite its violent disintegration. However, the team made an unexpected discovery: narrow spectral features at 4.5 and 5.1 microns, potentially indicating the presence of carbon dioxide (CO2) and nitric oxide (NO)—chemical compounds more commonly associated with icy bodies like comets rather than terrestrial mantles.
These surprising findings raised questions about the nature of the escaping material and indicated that, despite being highly heated and rapidly disintegrating, K2-22b’s composition might include substances that were previously thought to be absent in rocky planets so close to their stars. While the results were not as strong as hoped—due to observing the planet when its dust tail wasn’t as dense—the team is optimistic that future observations with JWST will refine these discoveries and deepen our understanding of exoplanetary interiors.
The MIT Discovery: BD+05 4868 A
Meanwhile, the MIT team, led by Marc Hon, a postdoctoral researcher, made a stunning discovery using the TESS (Transiting Exoplanet Survey Satellite). The team observed the planet BD+05 4868 Ab, orbiting the star BD+05 4868 A, which exhibited an even more extreme form of disintegration. This planet, located in the constellation Aries, is the closest and most rapidly disintegrating planet discovered so far, orbiting the star once every 30.5 hours—even faster than K2-22b.
The most intriguing feature of BD+05 4868 Ab’s disintegration is its massive dust tails, which are described as the largest dust tails ever observed from a disintegrating planet. These tails stretch a staggering 9 million kilometers—enough to encompass more than half the planet’s orbit around its star. Unlike K2-22b, which has a single comet-like tail, BD+05 4868 Ab displays two tails: a leading tail and a trailing tail, suggesting that different-sized dust grains are being ejected. The leading tail consists of larger grains, about the size of desert sand particles, while the trailing tail contains finer grains, comparable in size to soot.
Based on the observed size and intensity of the dust tails, the MIT team concluded that BD+05 4868 Ab is evaporating at a catastrophic rate, losing the equivalent of a moon’s worth of material every million years. Given the planet’s estimated mass—the same as Earth’s Moon—the team predicts that BD+05 4868 Ab will completely disintegrate in approximately 1 to 2 million years, an extremely rapid process in cosmic terms.
What makes this discovery even more significant is the star it orbits. BD+05 4868 A is approximately 100 times brighter than K2-22, making the study of BD+05 4868 Ab significantly easier. Most of the previously known disintegrating planets were around fainter stars, which complicated observations. As a result, BD+05 4868 Ab is now regarded as the benchmark for future studies of disintegrating planets.
Hon and his team are now working in collaboration with the Penn State team to submit a new proposal for JWST observations of BD+05 4868 A. The increased brightness of this star should yield high-quality data, allowing scientists to study its disintegrating planet in greater detail than ever before, potentially unlocking even deeper insights into exoplanetary composition and evolution.
Future Directions for Exoplanetary Research
Both the Penn State and MIT teams have demonstrated the potential of the JWST and TESS in studying exoplanets in ways previously unimaginable. JWST’s powerful capabilities, particularly in the mid-infrared range, allow astronomers to explore the composition of planetary materials escaping into space, shedding light on the interior structure of distant rocky planets.
By carefully analyzing the spectra of disintegrating planets, scientists are starting to piece together a clearer picture of how exoplanets—particularly those located near their host stars—evolve and degrade over time. These findings suggest that the study of these extreme planets could be a critical tool in understanding not just how exoplanets disintegrate, but also how planets are formed, how they maintain their material, and what happens to their elemental composition when exposed to the intense heat and radiation from nearby stars.
As more data is collected and the observation techniques refined, these studies could ultimately reveal new, surprising facts about rocky planets, their atmospheres, and their dynamic lifecycles in alien star systems. The work being done by the Penn State and MIT teams, along with the collaborations underway with the JWST, is expected to serve as a springboard for a new era of exoplanetary studies, marking the beginning of a deeper and more detailed exploration of the physical nature of planets beyond our solar system.
With this growing field of research, we can expect to learn not only about the extreme ends of planetary evolution, but also about the processes that may define the broader universe of rocky planets orbiting distant stars.
Conclusion
In conclusion, the recent discoveries by the Penn State and MIT teams have provided groundbreaking insights into the extreme phenomenon of planetary disintegration. By utilizing the James Webb Space Telescope (JWST) and TESS, astronomers have captured detailed observations of two ultra-short period (USP) planets—K2-22b and BD+05 4868 Ab—undergoing dramatic evaporation processes. These findings have not only revealed the dynamic and chaotic nature of disintegrating planets but also opened a new avenue for studying planetary interiors. Through the analysis of the emitted material, astronomers have gained rare glimpses into the composition of distant rocky worlds. As future studies with JWST continue to refine these observations, we stand on the threshold of a deeper understanding of exoplanetary evolution, including how planets disintegrate and what the composition of such planets might reveal about their formation. This research is setting the stage for a new frontier in planetary science and exoplanet exploration.
References: Marc Hon et al, A Disintegrating Rocky Planet with Prominent Comet-like Tails Around a Bright Star, arXiv (2025). DOI: 10.48550/arxiv.2501.05431
Nick Tusay et al, A Disintegrating Rocky World Shrouded in Dust and Gas: Mid-IR Observations of K2-22b using JWST, arXiv (2025). DOI: 10.48550/arxiv.2501.08301