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Early Release Science of the exoplanet WASP-39b with JWST NIRISS.

Published version
Peer-reviewed

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Authors

Radica, Michael 
Welbanks, Luis 
Murray, Catriona Anne 
Ohno, Kazumasa 

Abstract

The Saturn-mass exoplanet WASP-39b has been the subject of extensive efforts to determine its atmospheric properties using transmission spectroscopy1-4. However, these efforts have been hampered by modelling degeneracies between composition and cloud properties that are caused by limited data quality5-9. Here we present the transmission spectrum of WASP-39b obtained using the Single-Object Slitless Spectroscopy (SOSS) mode of the Near Infrared Imager and Slitless Spectrograph (NIRISS) instrument on the JWST. This spectrum spans 0.6-2.8 μm in wavelength and shows several water-absorption bands, the potassium resonance doublet and signatures of clouds. The precision and broad wavelength coverage of NIRISS/SOSS allows us to break model degeneracies between cloud properties and the atmospheric composition of WASP-39b, favouring a heavy-element enhancement ('metallicity') of about 10-30 times the solar value, a sub-solar carbon-to-oxygen (C/O) ratio and a solar-to-super-solar potassium-to-oxygen (K/O) ratio. The observations are also best explained by wavelength-dependent, non-grey clouds with inhomogeneous coverageof the planet's terminator.

Description

Keywords

Article, /639/33/34/862, /639/33/445/862, /140, article

Journal Title

Nature

Conference Name

Journal ISSN

0028-0836
1476-4687

Volume Title

614

Publisher

Springer Science and Business Media LLC