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

Feinstein, Adina D; Radica, Michael; Welbanks, Luis; Murray, Catriona Anne; Ohno, Kazumasa; Coulombe, Louis-Philippe; Espinoza, Néstor; Bean, Jacob L; Teske, Johanna K; Benneke, Björn; Line, Michael R; Rustamkulov, Zafar; Saba, Arianna; Tsiaras, Angelos; Barstow, Joanna K.; Fortney, Jonathan J; Gao, Peter; Knutson, Heather A; MacDonald, Ryan J; Mikal-Evans, Thomas; Rackham, Benjamin V; Taylor, Jake; Parmentier, Vivien; Batalha, Natalie M; Berta-Thompson, Zachory K; Carter, Aarynn L; Changeat, Quentin; Dos Santos, Leonardo A; Gibson, Neale P; Goyal, Jayesh M; Kreidberg, Laura; López-Morales, Mercedes; Lothringer, Joshua D; Miguel, Yamila; Molaverdikhani, Karan; Moran, Sarah E; Morello, Giuseppe; Mukherjee, Sagnick; Sing, David K; Stevenson, Kevin B; Wakeford, Hannah R; Ahrer, Eva-Maria; Alam, Munazza K; Alderson, Lili; Allen, Natalie H; Batalha, Natasha E; Bell, Taylor J; Blecic, Jasmina; Brande, Jonathan; Caceres, Claudio; Casewell, S L; Chubb, Katy L; Crossfield, Ian J M; Crouzet, Nicolas; Cubillos, Patricio E; Decin, Leen; Désert, Jean-Michel; Harrington, Joseph; Heng, Kevin; Henning, Thomas; Iro, Nicolas; Kempton, Eliza M-R; Kendrew, Sarah; Kirk, James; Krick, Jessica; Lagage, Pierre-Olivier; Lendl, Monika; Mancini, Luigi; Mansfield, Megan; May, E M; Mayne, N J; Nikolov, Nikolay K; Palle, Enric; de la Roche, Dominique J M Petit Dit; Piaulet, Caroline; Powell, Diana; Redfield, Seth; Rogers, Laura K; Roman, Michael T; Roy, Pierre-Alexis; Nixon, Matthew C; Schlawin, Everett; Tan, Xianyu; Tremblin, P; Turner, Jake D; Venot, Olivia; Waalkes, William C; Wheatley, Peter J and Zhang, Xi (2023). Early Release Science of the exoplanet WASP-39b with JWST NIRISS. Nature, 614(7949) pp. 670–675.

DOI: https://doi.org/10.1038/s41586-022-05674-1


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 0.6-2.8𝝻m 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.

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