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Early Release Science of the exoplanet WASP-39b with JWST NIRSpec PRISM

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Peer-reviewed

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Authors

Mukherjee, S. 
May, E. M. 
Kirk, J. 

Abstract

Transmission spectroscopy1–3 of exoplanets has revealed signatures of water vapour, aerosols and alkali metals in a few dozen exoplanet atmospheres4, 5. However, these previous inferences with the Hubble and Spitzer Space Telescopes were hindered by the observations’ relatively narrow wavelength range and spectral resolving power, which precluded the unambiguous identification of other chemical species—in particular the primary carbon-bearing molecules6, 7. Here we report a broad-wavelength 0.5–5.5 µm atmospheric transmission spectrum of WASP-39b8, a 1,200 K, roughly Saturn-mass, Jupiter-radius exoplanet, measured with the JWST NIRSpec’s PRISM mode9 as part of the JWST Transiting Exoplanet Community Early Release Science Team Program10–12. We robustly detect several chemical species at high significance, including Na (19σ), H2O (33σ), CO2 (28σ) and CO (7σ). The non-detection of CH4, combined with a strong CO2 feature, favours atmospheric models with a super-solar atmospheric metallicity. An unanticipated absorption feature at 4 µm is best explained by SO2 (2.7σ), which could be a tracer of atmospheric photochemistry. These observations demonstrate JWST’s sensitivity to a rich diversity of exoplanet compositions and chemical processes.

Description

Acknowledgements: This work is based on observations made with the NASA/ESA/CSA JWST. The data were obtained from the Mikulski Archive for Space Telescopes at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract no. NAS 5-03127 for JWST. These observations are associated with program no. JWST-ERS-01366. Support for program no. JWST-ERS-01366 was provided by NASA through a grant from the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract no. NAS 5-03127. This work benefited from the 2022 Exoplanet Summer Program in the Other Worlds Laboratory at the University of California, Santa Cruz, a program supported by the Heising-Simons Foundation. We thank E. Agol for constructive comments.

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Journal Title

Nature

Conference Name

Journal ISSN

0028-0836
1476-4687

Volume Title

614

Publisher

Nature Publishing Group UK