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Blue Skies and Glass Rain: Silicate Clouds on the Dayside of HD 189733 b

Presentation #501.05 in the session Atmospheres and Interiors of Giant Planets.

Published onApr 03, 2024
Blue Skies and Glass Rain: Silicate Clouds on the Dayside of HD 189733 b

Recent mid-infrared observations with JWST/MIRI have resulted in the first direct detections of absorption features from silicate clouds in the transmission spectra of two transiting exoplanets, WASP-17 b and WASP-107 b. Here, we present the extremely precise mid-infrared (5−12 μm) dayside emission spectrum of the benchmark hot Jupiter HD 189733 b with MIRI LRS by combining data from two secondary eclipse observations. We confirm the previous detection of water absorption at 6.5 μm from Spitzer/IRS, and place these new mid-infrared observations in context with the wealth of observations of this planet from Spitzer and HST. We detect a new absorption feature at 8.7 μm and show that it is consistent with the presence of small (∼0.01 μm) grains of SiO2[s] in the uppermost layers of HD 189733 b’s dayside atmosphere. This is the first direct detection of silicate clouds in HD 189733 b’s atmosphere, and the first detection of silicate clouds on the dayside of any hot Jupiter. When combined with other JWST observations of HD 189733 b’s transmission and emission spectrum at shorter wavelengths, these observations will provide us with the most detailed picture to date of the atmospheric composition and cloud properties of this benchmark hot Jupiter.

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