JWST observations and new models reveal how silicate clouds form in exoplanet atmospheres

Star system: VHS 1256-1257 A | Distance from the Sun: 69 light years

The James Webb Space Telescope (JWST) has detected silicate clouds in the atmospheres of several exoplanets, providing new insights into how clouds form in extreme environments. While simple models can fit these observations, they do not always match the results from more detailed microphysical models. To address this, researchers developed Nimbus, a fast model that simulates cloud formation based on physical processes, and used it alongside Virga, a model that balances how particles settle and mix in the atmosphere.

The team studied four exoplanets—WASP-107 b, WASP-17 b, VHS-1256 b, and YSES-1 c—and found that all have very small silicate particles high in their atmospheres. These tiny particles can only be explained if cloud particles settle very slowly or if they grow inefficiently due to low sticking rates. The study also found that the rate at which particles stick together affects how thick the clouds are, and this can be measured by looking at the planet’s spectrum across a wide range of wavelengths. The sticking rates found for some planets match those seen in laboratory experiments on Earth. The research highlights the importance of using data from many wavelengths to understand cloud formation on exoplanets.

Key findings
- JWST detected silicate clouds in four exoplanet atmospheres
- New models show that slow settling or low sticking rates explain the presence of tiny cloud particles
- The sticking rate controls the vertical thickness of clouds and can be measured from the planet’s spectrum
- Some exoplanet cloud properties match laboratory results from Earth
- Observations across a wide range of wavelengths are crucial for understanding exoplanet clouds

Scientific study

Connecting JWST Silicate Cloud Observations to Exoplanet Cloud Microphysics with Nimbus (external link)