SO$_2$, silicate clouds, but no CH$_4$ detected in a warm Neptune

Author(s)

Achrène Dyrek, Michiel Min, Leen Decin, Jeroen Bouwman, Nicolas Crouzet, Paul Mollière, Pierre-Olivier Lagage, Thomas Konings, Pascal Tremblin, Manuel Güdel, John Pye, Rens Waters, Thomas Henning, Bart Vandenbussche, Francisco Ardevol Martinez, Ioannis Argyriou, Elsa Ducrot, Linus Heinke, Gwenael Van Looveren, Olivier Absil, David Barrado, Pierre Baudoz, Anthony Boccaletti, Christophe Cossou, Alain Coulais, Billy Edwards, René Gastaud, Alistair Glasse, Adrian Glauser, Thomas P. Greene, Sarah Kendrew, Oliver Krause, Fred Lahuis, Michael Mueller, Goran Olofsson, Polychronis Patapis, Daniel Rouan, Pierre Royer, Silvia Scheithauer, Ingo Waldmann, Niall Whiteford, Luis Colina, Ewine F. van Dishoeck, Göran Ostlin, Tom P. Ray, Gillian Wright

Abstract

WASP-107b is a warm (approximately 740 K) transiting planet with a Neptune-like mass of roughly 30.5 M

_⊕ and Jupiter-like radius of about 0.94 R

_J (refs.

^1,2), whose extended atmosphere is eroding

³. Previous observations showed evidence for water vapour and a thick, high-altitude condensate layer in the atmosphere of WASP-107b (refs.

^4,5). Recently, photochemically produced sulfur dioxide (SO

₂) was detected in the atmosphere of a hot (about 1,200 K) Saturn-mass planet from transmission spectroscopy near 4.05 μm (refs.

^6,7), but for temperatures below about 1,000 K, sulfur is predicted to preferably form sulfur allotropes instead of SO

₂ (refs.

^8–10). Here we report the 9σ detection of two fundamental vibration bands of SO

₂, at 7.35 μm and 8.69 μm, in the transmission spectrum of WASP-107b using the Mid-Infrared Instrument (MIRI) of JWST. This discovery establishes WASP-107b as the second irradiated exoplanet with confirmed photochemistry, extending the temperature range of exoplanets exhibiting detected photochemistry from about 1,200 K down to about 740 K. Furthermore, our spectral analysis reveals the presence of silicate clouds, which are strongly favoured (around 7σ) over simpler cloud set-ups. Furthermore, water is detected (around 12σ) but methane is not. These findings provide evidence of disequilibrium chemistry and indicate a dynamically active atmosphere with a super-solar metallicity.

Organisation(s)

Department of Astrophysics

External organisation(s)

Université Paris Saclay, Katholieke Universiteit Leuven, SRON Netherlands Institute for Space Research , Université Paris-Cité, Stockholm University, Max-Planck-Institut für Astronomie, Leiden University, University of Leicester, Eidgenössische Technische Hochschule Zürich, Radboud University, University of Groningen, University of Edinburgh, Université de Liège, Centro de Astrobiología (CSIC-INTA), The Royal Observatory, Edinburgh, NASA Ames Research Center, European Space Agency (ESA), Baltimore, University College London, American Museum of Natural History, Dublin Institute for Advanced Studies

Journal

Nature

Volume

625

Pages

51-54

No. of pages

4

ISSN

0028-0836

DOI

https://doi.org/10.1038/s41586-023-06849-0

Publication date

01-2024

Peer reviewed

Yes

Austrian Fields of Science 2012

103004 Astrophysics

Keywords

Portal url

https://ucrisportal.univie.ac.at/en/publications/fc8fae36-332b-45a1-b3b9-9cc3204fb4b8