A precise metallicity and carbon-to-oxygen ratio for a warm giant exoplanet from its panchromatic JWST emission spectrum
WASP-80 b, a warm sub-Jovian (equilibrium temperature [Formula: see text]820 K, 0.5 Jupiter masses), presents an opportunity to characterize a rare gas giant exoplanet around a low-mass star. In addition, its moderate temperature enables its atmosphere to host a range of carbon and oxygen species (H<sub>2</sub>O, CH<sub>4</sub>, CO, CO<sub>2</sub>, NH<sub>3</sub>). In this paper, we present a panchromatic emission spectrum of WASP-80 b, the first gas giant around a late K/early M-dwarf star and the coolest planet for which the James Webb Space Telescope has obtained a complete emission spectrum spanning 2.4 to 12 [Formula: see text]m, including NIRCam F322W2 (2.4 to 4 [Formula: see text]m) and F444W (4 to 5 [Formula: see text]m), and MIRI LRS (5 to 12 [Formula: see text]m). We report confident detections of H<sub>2</sub>O, CH<sub>4</sub>, CO, and CO<sub>2</sub>, and a tentative detection of NH<sub>3</sub>. We estimate WASP-80 b's atmospheric metallicity and carbon-to-oxygen ratio and compare them with estimates for other gas giants. Despite the relative rarity of giant planets around low-mass stars, we find that WASP-80 b's composition is consistent with other hot gas giants, suggesting that the formation pathway of WASP-80 b may not be dissimilar from hot gas giants around higher-mass stars.
Authors
- Sagnick Mukherjee (ORCID: https://orcid.org/0000-0003-1622-1302)
- Matthew M. Murphy (ORCID: https://orcid.org/0000-0002-8517-8857)
- Luis Welbanks (ORCID: https://orcid.org/0000-0003-0156-4564)
- Jonathan J. Fortney (ORCID: https://orcid.org/0000-0002-9843-4354)
- Kazumasa Ohno (ORCID: https://orcid.org/0000-0003-3290-6758)
- Lindsey S. Wiser (ORCID: https://orcid.org/0000-0002-3295-1279)
- Thomas P. Greene (ORCID: https://orcid.org/0000-0002-8963-8056)
- Thomas G. Beatty (ORCID: https://orcid.org/0000-0002-9539-4203)
- Taylor J. Bell (ORCID: https://orcid.org/0000-0003-4177-2149)
- Kam Arnold (ORCID: https://orcid.org/0000-0002-3407-5305)
- Vivien Parmentier (ORCID: https://orcid.org/0000-0001-9521-6258)
- Everett Schlawin (ORCID: https://orcid.org/0000-0001-8291-6490)
- Michael R. Line (ORCID: https://orcid.org/0000-0002-2338-476X)
- Nishil Mehta (ORCID: https://orcid.org/0000-0001-6086-4175)
Institutions
- Ames Research Center (US)
- Space Telescope Science Institute (US)
- University of Wisconsin–Madison (US)
- University of Arizona (US)
- University of California, Santa Cruz (US)
- Université Côte d'Azur (FR)
- NASA Research Park (US)
- European Space Agency (FR)
- Bay Area Environmental Research Institute (US)
- Astrobiology Center (JP)
- Observatoire de la Côte d’Azur (FR)
- National Astronomical Observatory of Japan (JP)
- Arizona State University (US)
- LaGrange College (US)
Publication Details
- Journal
- Proceedings of the National Academy of Sciences
- Published
- 2025-09-22
- DOI
- https://doi.org/10.1073/pnas.2416193122
- Citations
- 5
- Primary Topic
- Stellar, planetary, and galactic studies
- Type
- article
- Field-Weighted Citation Impact
- 5.77