Exoplanets & Exomoons

Methane Throughout The Atmosphere Of The Warm Exoplanet WASP-80b

By Keith Cowing
Status Report
September 11, 2023
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Methane Throughout The Atmosphere Of The Warm Exoplanet WASP-80b
Spectroscopic and broadband NIRCam F322W2 lightcurves of the transit and eclipse of WASP-80b. The raw spectroscopic transit (a) and eclipse (b) lightcurves after spectral binning (0.0146 µm bins) but without any temporal binning. The transit and eclipse’s second and third contact points are indicated with red lines above the plots. The broadband (2.420–4.025 µm) transit (c) and eclipse (d) lightcurves are shown in gray without error bars. The transit and eclipse’s second and third contact points are indicated with red vertical lines. Black points with 1σ error bars show temporally binned data with a cadence of 5 minutes; note that the error bars in panel c are smaller than the point size. BJDTDB is the date in the Barycentric Julian Date in the Barycentric Dynamical Time system. — astro-ph.EP

The abundances of major carbon and oxygen bearing gases in the atmospheres of giant exoplanets provide insights into atmospheric chemistry and planet formation processes.

Thermochemistry suggests that methane should be the dominant carbon-bearing species below ∼1000 K over a range of plausible atmospheric compositions; this is the case for the Solar System planets and has been confirmed in the atmospheres of brown dwarfs and self-luminous directly imaged exoplanets.

However, methane has not yet been definitively detected with space-based spectroscopy in the atmosphere of a transiting exoplanet, but a few detections have been made with ground-based, high-resolution transit spectroscopy including a tentative detection for WASP-80b. Here we report transmission and emission spectra spanning 2.4-4.0 micrometers of the 825 K warm Jupiter WASP-80b taken with JWST’s NIRCam instrument, both of which show strong evidence for methane at greater than 6-sigma significance.

The derived methane abundances from both viewing geometries are consistent with each other and with solar to sub-solar C/O and ~5× solar metallicity, which is consistent with theoretical predictions.

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

Comments: 23 pages, 10 figures, 3 tables. This preprint has been submitted to and accepted in principle for publication in Nature without significant changes
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:2309.04042 [astro-ph.EP] (or arXiv:2309.04042v1 [astro-ph.EP] for this version)
Submission history
From: Taylor J. Bell
[v1] Thu, 7 Sep 2023 23:13:09 UTC (16,768 KB)
Astrobiolgy, Astrochemistry

Explorers Club Fellow, ex-NASA Space Station Payload manager/space biologist, Away Teams, Journalist, Lapsed climber, Synaesthete, Na’Vi-Jedi-Freman-Buddhist-mix, ASL, Devon Island and Everest Base Camp veteran, (he/him) 🖖🏻