Sand clouds and rock rains: James Webb studied the atmosphere of a “swollen” exoplanet

Using the capabilities of the James Webb Telescope (JWST), a team of European astronomers studied the atmosphere of the “swollen” exoplanet WASP-107b. They managed to find water vapour, sulfur and even sand clouds there.

WASP-107b in the artist’s image. Source: Klaas Verpoest, Johan Van Looveren, Leen Decin

WASP-107b orbits an orange dwarf located 200 light-years from Earth. Its orbit passes at a distance of only 0.056 AU (8.4 million km) from the parent star. This world is one of the most “bloated” exoplanets known to astronomers. WASP-107b is comparable in size to the diameter of Jupiter, but its mass is only 12% of Jupiter’s. The exoplanet has a very prolonged atmosphere, extending into the surrounding space for tens of thousands of kilometres.

This feature makes WASP-107b a very attractive target for astronomers, because it allows them to look into the inner layers of its atmosphere. To this end, they used JWST. Observations made in the mid-infrared range allowed them to make a number of discoveries. So, JWST failed to find any traces of methane, indicating a potentially warm bowels of the planet.

The spectrum of the exoplanet WASP-107b. Source: Michiel Min / European MIRI EXO GTO team / ESA / NASA

At the same time, sulfur dioxide was found in the atmosphere of WASP-107b, which was a big surprise for the researchers, because previous models predicted its absence. Apparently, it’s all about the “fluffiness” of the exoplanet. Because of it, high-energy photons can penetrate deep into the atmosphere and trigger the reactions necessary for the formation of sulfur dioxide.

JWST also managed to find traces of water vapour in the atmosphere of WASP-107b. But perhaps the most interesting find was the silicate particles that made up its clouds. Terrestrial clouds consist of water droplets and water ice crystals. But on WASP-107b, where the atmosphere is heated to very high temperatures, silicates play this role. Their vapours rise up, condense and form silicate clouds, from which rock rains fall from time to time. After that, the whole cycle repeats.

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