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

Taylor J Bell; Luis Welbanks; Everett Schlawin; Michael R Line; Jonathan J Fortney; Thomas P Greene; Kazumasa Ohno; Vivien Parmentier; Emily Rauscher; Thomas G Beatty; Sagnick Mukherjee; Lindsey S Wiser; Martha L Boyer; Marcia J Rieke; John A Stansberry

doi:10.1038/s41586-023-06687-0

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

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

Authors

Taylor J Bell^{1

2}, Luis Welbanks³, Everett Schlawin⁴, Michael R Line³, Jonathan J Fortney⁵, Thomas P Greene⁶, Kazumasa Ohno^{5

7}, Vivien Parmentier⁸, Emily Rauscher⁹, Thomas G Beatty¹⁰, Sagnick Mukherjee⁵, Lindsey S Wiser³, Martha L Boyer¹¹, Marcia J Rieke⁴, John A Stansberry¹¹

Affiliations

¹ Bay Area Environmental Research Institute, NASA Ames Research Center, Moffett Field, CA, USA. [email protected].
² Space Science and Astrobiology Division, NASA Ames Research Center, Moffett Field, CA, USA. [email protected].
³ School of Earth and Space Exploration, Arizona State University, Tempe, AZ, USA.
⁴ Steward Observatory, University of Arizona, Tucson, AZ, USA.
⁵ Department of Astronomy and Astrophysics, University of California Santa Cruz, Santa Cruz, CA, USA.
⁶ Space Science and Astrobiology Division, NASA Ames Research Center, Moffett Field, CA, USA.
⁷ Division of Science, National Astronomical Observatory of Japan, Tokyo, Japan.
⁸ Laboratoire Lagrange, Observatoire de la Côte d'Azur, Université Côte d'Azur, Nice, France.
⁹ Department of Astronomy, University of Michigan, Ann Arbor, MI, USA.
¹⁰ Department of Astronomy, University of Wisconsin-Madison, Madison, WI, USA.
¹¹ Space Telescope Science Institute, Baltimore, MD, USA.

PMID: 37993572
DOI: 10.1038/s41586-023-06687-0

Abstract

The abundances of main carbon- and oxygen-bearing gases in the atmospheres of giant exoplanets provide insights into atmospheric chemistry and planet formation processes^1,2. 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 exoplanet^6-11, but a few detections have been made with ground-based, high-resolution transit spectroscopy^12,13 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 predictions^15-17.