Early Release Science of the exoplanet WASP-39b with JWST NIRISS
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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-39 b obtained using the SOSS mode of the NIRISS instrument on JWST. This spectrum spans 0.6–2.8 μm in wavelength and reveals multiple 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 ~10–30x 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-gray clouds with inhomogeneous coverage of the planet’s terminator.
Feinstein , A D , Radica , M , Welbanks , L , Murray , C A , Ohno , K , Coulombe , L-P , Espinoza , N , Bean , J L , Teske , J K , Benneke , B , Line , M R , Rustamkulov , Z , Saba , A , Tsiaras , A , Barstow , J K , Fortney , J J , Gao , P , Knutson , H A , MacDonald , R J , Mikal-Evans , T , Rackham , B V , Taylor , J , Parmentier , V , Batalha , N M , Berta-Thompson , Z K , Carter , A L , Changeat , Q , Dos Santos , L A , Gibson , N P , Goyal , J M , Kreidberg , L , López-Morales , M , Lothringer , J D , Miguel , Y , Molaverdikhani , K , Moran , S E , Morello , G , Mukherjee , S , Sing , D K , Stevenson , K B , Wakeford , H R , Ahrer , E-M , Alam , M K , Alderson , L , Allen , N H , Batalha , N E , Bell , T J , Blecic , J , Brande , J , Caceres , C , Casewell , S L , Chubb , K L , Crossfield , I J M , Crouzet , N , Cubillos , P E , Decin , L , Désert , J-M , Harrington , J , Heng , K , Henning , T , Iro , N , Kempton , E M -R , Kendrew , S , Kirk , J , Krick , J , Lagage , P-O , Lendl , M , Mancini , L , Mansfield , M , May , E M , Mayne , N J , Nikolov , N K , Palle , E , de la Roche , D J M P D , Piaulet , C , Powell , D , Redfield , S , Rogers , L K , Roman , M T , Roy , P-A , Nixon , M C , Schlawin , E , Tan , X , Tremblin , P , Turner , J D , Venot , O , Waalkes , W C , Wheatley , P J & Zhang , X 2023 , ' Early Release Science of the exoplanet WASP-39b with JWST NIRISS ' , Nature . https://doi.org/10.1038/s41586-022-05674-1
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DescriptionSupport for this program was provided by NASA through a grant from the Space Telescope Science Institute. ADF acknowledges support by the National Science Foundation Graduate Research Fellowship Program under Grant No. DGE-1746045. MR acknowledges support from the National Sciences and Engineering Research Council of Canada, the Fonds de Recherche du Québec, as well as the Institut de Recherche sur les Exoplanètes.
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