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