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. 2023 Nov;623(7988):709-712.
doi: 10.1038/s41586-023-06687-0. Epub 2023 Nov 22.

Methane throughout the atmosphere of the warm exoplanet WASP-80b

Taylor J Bell  1   2 , Luis Welbanks  3 , Everett Schlawin  4 , Michael R Line  3 , Jonathan J Fortney  5 , Thomas P Greene  6 , Kazumasa Ohno  5   7 , Vivien Parmentier  8 , Emily Rauscher  9 , Thomas G Beatty  10 , Sagnick Mukherjee  5 , Lindsey S Wiser  3 , Martha L Boyer  11 , Marcia J Rieke  4 , John A Stansberry  11
Affiliations

Methane throughout the atmosphere of the warm exoplanet WASP-80b

Taylor J Bell et al. Nature. 2023 Nov.

Abstract

The abundances of main carbon- and oxygen-bearing gases in the atmospheres of giant exoplanets provide insights into atmospheric chemistry and planet formation processes1,2. Thermochemistry suggests that methane (CH4) should be the dominant carbon-bearing species below about 1,000 K over a range of plausible atmospheric compositions3; this is the case for the solar system planets4 and has been confirmed in the atmospheres of brown dwarfs and self-luminous, directly imaged exoplanets5. However, CH4 has not yet been definitively detected with space-based spectroscopy in the atmosphere of a transiting exoplanet6-11, but a few detections have been made with ground-based, high-resolution transit spectroscopy12,13 including a tentative detection for WASP-80b (ref. 14). Here we report transmission and emission spectra spanning 2.4-4.0 μm of the 825 K warm Jupiter WASP-80b taken with the NIRCam instrument of the JWST, both of which show strong evidence of CH4 at greater than 6σ significance. The derived CH4 abundances from both viewing geometries are consistent with each other and with solar to sub-solar C/O and around five times solar metallicity, which is consistent with theoretical predictions15-17.

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