10-06-2025
Iron May Rain From Sand Clouds on Newly-Discovered Planet
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Dusty clouds made of sand—that may rain iron—blanket a giant planet orbiting a young, sun-like star just 310 light-years from Earth, the James Webb Space Telescope has revealed.
The discovery was made by an international team of astronomers led from the Space Telescope Science Institute (STScI) in Baltimore Maryland.
Around the star—dubbed "YSES-1"—the researchers also directly observed another giant exoplanet around which is a potentially multiple-moon-forming circumplanetary disk.
"This work highlights the incredible abilities of JWST to characterize exoplanet atmospheres," said paper author and astronomer Evert Nasedkin of Trinity College Dublin, Ireland, in a statement.
"With only a handful of exoplanets that can be directly imaged, the YSES-1 system offers unique insights into the atmospheric physics and formation processes of these distant giants."
An artist's impression of the planets of the star system YSES-1.
An artist's impression of the planets of the star system YSES-1.
Ellis Bogat
Using Webb's Near InfraRed Spectrograph (NIRSpec), the team were able to capture the two planets—which are both several times larger than Jupiter, and orbit out far from their host star—in a single exposure.
This has provided what lead author and STScI physicist Kielan Hoch calls "the most detailed dataset of a multi-planet system to date."
Nasedkin added: "Directly imaged exoplanets—planets outside our own solar system—are the only exoplanets that we can truly take photos of.
"These exoplanets are typically still young enough that they are still hot from their formation—and it is this warmth, seen in the thermal infrared, that we as astronomers observe."
By recording the light coming from the two exoplanets, the team were able to unpick the signals that reveal the chemical makeup of the gas giant's atmospheres.
"When we looked at the smaller, farther-out companion—known as YSES-1c—we found the tell-tale signature of silicate clouds in the mid-infrared," said Nasedkin.
"Essentially made of sand-like particles, this is the strongest silicate absorption feature observed in an exoplanet yet."
The team's analysis also indicated that the clouds contain iron, which may fall from the clouds down into the planet as rain.
"We believe this is linked to the relative youth of the planets: younger planets are slightly larger in radius, and this extended atmosphere may allow the cloud to absorb more of the light emitted by the planet."
The circumplanetary disk is the inner planet, YSES-1b, meanwhile, presents something of a mystery.
Only three other such disks have been identified to date, but they are all around objects that are significantly younger than YSES-1b—leading to questions as to how the newly discovered disk could be so long-lived.
And that is far from the only puzzle that will need to be solved.
"The YSES-1 system planets are also too widely separated to be explained through current formation theories, so the additional discoveries of distinct silicate clouds around YSES-1c and small hot dusty material around YSES-1b leads to more mysteries and complexities for determining how planets form and evolve," Hoch concluded.
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Reference
Hoch, K. K. W., Rowland, M., Petrus, S., Nasedkin, E., Ingebretsen, C., Kammerer, J., Perrin, M., D'Orazi, V., Balmer, W. O., Barman, T., Bonnefoy, M., Chauvin, G., Chen, C., De Rosa, R. J., Girard, J., Gonzales, E., Kenworthy, M., Konopacky, Q. M., Macintosh, B., Moran, S. E., Morley, C. V., Palma-Bifani, P., Pueyo, L., Ren, B., Rickman, E., Ruffio, J.-B., Theissen, C. A., Ward-Duong, K., & Zhang, Y. (2025). Silicate clouds and a circumplanetary disk in the YSES-1 exoplanet system. Nature.
