Early Release Science of the exoplanet WASP-39b with JWST NIRCam
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Measuring the metallicity and carbon-to-oxygen (C/O) ratio in exoplanet atmospheres is a fundamental step towards constraining the dominant chemical processes at work and, if in equilibrium, revealing planet formation histories. Transmission spectroscopy e.g., refs.1,2) provides the necessary means by constraining the abundances of oxygen- and carbon-bearing species; however, this requires broad wavelength coverage, moderate spectral resolution, and high precision that, together, are not achievable with previous observatories. Now that JWST has commenced science operations, we are able to observe exoplanets at previously uncharted wavelengths and spectral resolutions. Here we report time-series observations of the transiting exoplanet WASP-39b using JWST’s Near InfraRed Camera (NIRCam). The long-wavelength spectroscopic and short-wavelength photometric light curves span 2.0 – 4.0 µm, exhibit minimal systematics, and reveal well-defined molecular absorption features in the planet’s spectrum. Specifically, we detect gaseous H2O in the atmosphere and place an upper limit on the abundance of CH4. The otherwise prominent CO2 feature at 2.8 µm is largely masked by H2O. The best-fit chemical equilibrium models favour an atmospheric metallicity of 1–100× solar (i.e., an enrichment of elements heavier than helium relative to the Sun) and a sub-stellar carbon-to-oxygen (C/O) ratio. The inferred high metallicity and low C/O ratio may indicate significant accretion of solid materials during planet formation (e.g., refs.3,4) or disequilibrium processes in the upper atmosphere (e.g., refs.5,6).
Ahrer , E-M , Stevenson , K B , Mansfield , M , Moran , S E , Brande , J , Morello , G , Murray , C A , Nikolov , N K , Petit dit de la Roche , D J M , Schlawin , E , Wheatley , P J , Zieba , S , Batalha , N E , Damiano , M , Goyal , J M , Lendl , M , Lothringer , J D , Mukherjee , S , Ohno , K , Batalha , N M , Battley , M P , Bean , J L , Beatty , T G , Benneke , B , Berta-Thompson , Z K , Carter , A L , Cubillos , P E , Daylan , T , Espinoza , N , Gao , P , Gibson , N P , Gill , S , Harrington , J , Hu , R , Kreidberg , L , Lewis , N K , Line , M R , López-Morales , M , Parmentier , V , Powell , D K , Sing , D K , Tsai , S-M , Wakeford , H R , Welbanks , L , Alam , M K , Alderson , L , Allen , N H , Anderson , D R , Barstow , J K , Bayliss , D , Bell , T J , Blecic , J , Bryant , E M , Burleigh , M R , Carone , L , Casewell , S L , Changeat , Q , Chubb , K L , Crossfield , I J M , Crouzet , N , Decin , L , Désert , J-M , Feinstein , A D , Flagg , L , Fortney , J J , Gizis , J E , Heng , K , Iro , N , Kempton , E M -R , Kendrew , S , Kirk , J , Knutson , H A , Komacek , T D , Lagage , P-O , Leconte , J , Lustig-Yaeger , J , MacDonald , R J , Mancini , L , May , E M , Mayne , N J , Miguel , Y , Mikal-Evans , T , Molaverdikhani , K , Palle , E , Piaulet , C , Rackham , B V , Redfield , S , Rogers , L K , Roy , P-A , Rustamkulov , Z , Shkolnik , E L , Sotzen , K S , Taylor , J , Tremblin , P , Tucker , G S , Turner , J D , de Val-Borro , M , Venot , O & Zhang , X 2023 , ' Early Release Science of the exoplanet WASP-39b with JWST NIRCam ' , Nature , vol. 614 , no. 7949 , pp. 653–658 . https://doi.org/10.1038/s41586-022-05590-4
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DescriptionFunding: The NGTS facility is operated by a consortium of institutes with support from the UK Science and Technology Facilities Council (STFC) under projects ST/M001962/1, ST/S002642/1 and ST/W003163/1. This paper includes data collected by the TESS mission, obtained from MAST at STScI. Funding for the TESS mission is provided by the NASA’s Science Mission Directorate. This article is supported by the UK Research and Innovation (UKRI) to fund open access through the University of Warwick.
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