Seeing sand in another world’s sky is like watching the building blocks of planets rain down—this is the dawn of planetary science!
Key Points at a Glance
- JWST detected silicate (“sand”) clouds in the atmosphere of YSES‑1 c—the strongest ever seen on an exoplanet.
- The sibling planet YSES‑1 b hosts a circumplanetary dust disk, likely a nursery for future moons.
- These two worlds, orbiting a 16-million-year-old Sun-like star, defy existing planet‑formation theories.
- The discoveries illuminate real-time processes of planetary growth, atmosphere development, and moon formation.
Using the James Webb Space Telescope’s powerful infrared spectrometer, an international team led by Dr Kielan Hoch and Dr Evert Nasedkin peered at two massive gas giants orbiting the young star YSES‑1—about 307–310 light‑years away—capturing the most vivid snapshots yet of planetary infancy.
The outer planet, YSES‑1 c, is roughly six times the mass of Jupiter and lies far from its host star. In its upper atmosphere, JWST spotted a pronounced absorption signature at 9–11 µm, matching silicate minerals like iron-enriched pyroxene and magnesium silicates—tiny, sub‑micron “sand” grains floating in the sky. This is the strongest silicate cloud feature ever recorded on an exoplanet and may even hint at sandy rain in its atmosphere.
This discovery was made possible by the planet’s youth: at just 16.7 million years old, YSES‑1 c is still puffed up and hot from its formation, giving it an extended, glowing atmosphere ideal for JWST’s sensors. The data allowed scientists to model not only the cloud’s composition but also the shape and size of the particles within—an unprecedented atmospheric fingerprint from a world we’ve never visited.
Its sibling, YSES‑1 b, revealed an equally tantalizing feature: a dusty circumplanetary disk encircling the planet itself. These kinds of disks are rare—only three have been spotted before—and are believed to seed the formation of moons, much like Jupiter’s Galilean companions. But YSES‑1 b’s disk is especially puzzling. The host star is too old for typical planet-forming disks to remain, yet this one persists, raising new questions about moon formation longevity.
Because both planets orbit far from their host star and are directly observable, the YSES‑1 system serves as a Rosetta Stone for planetary science. The data challenges prevailing theories about how gas giants form, especially those with wide orbits. Their strange separation, paired with complex atmospheric and disk features, signals that our models may need a rethink.
The research also underscores JWST’s revolutionary power: its ability to simultaneously capture both planets in a single field of view was predicted even before launch, making this dual‑planet dataset the most detailed of its kind to date. These insights were powered by a cohort of early-career researchers—postdocs and graduate students whose creativity drove the success of the project.
Ultimately, by watching these alien giants evolve in real-time, astronomers are learning what our own solar system might have looked like in its chaotic infancy. These silicate clouds and dusty disks are more than curiosities—they’re cosmic breadcrumbs guiding us back to the origins of planetary life itself.
Source: Trinity College Dublin
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