SO₂, silicate clouds, but no CH₄ detected in a warm Neptune

January 2024 • 2024Natur.625...51D

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

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 eroding³. 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 (SO₂) 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 SO₂ (refs. ^8-10). Here we report the 9σ detection of two fundamental vibration bands of SO₂, 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.

Links

• SIMBAD https://simbad.u-strasbg.fr/simbad/sim-ref?querymethod=bib&simbo=on&submit=submit+bibcode&bibcode=2024Natur.625...51D
• PREPRINT http://arxiv.org/abs/2311.12515
• DATA http://heasarc.gsfc.nasa.gov/cgi-bin/W3Browse/biblink.pl?code=2024Natur.625...51D
• DATA https://archive.stsci.edu/
• DATA https://archive.stsci.edu/mastbibref.php?bibcode=2024Natur.625...51D
• DATA https://archive.stsci.edu/mastbibref.php?bibcode=2024Natur.625...51D
• DATA https://doi.org/10.17909/as3s-x893
• DATA https://heasarc.gsfc.nasa.gov/cgi-bin/W3Browse/swift.pl
• DATA https://hst.esac.esa.int/ehst/#/pages/search;bibcode=2024Natur.625...51D
• DATA https://nxsa.esac.esa.int/nxsa-web/#bibcode=2024Natur.625...51D
• DATA https://nxsa.esac.esa.int/nxsa-web/#search
• ELECTR https://doi.org/10.1038%2Fs41586-023-06849-0