Early Release Science of the exoplanet WASP-39b with JWST NIRISS
Adina D. Feinstein, Michael Radica, Luis Welbanks, C. A. Murray, Kazumasa Ohno, Louis-Philippe Coulombe, Néstor Espinoza, Jacob L. Bean, Johanna Teske, Björn Benneke, Michael Line, Zafar Rustamkulov, Arianna Saba, Angelos Tsiaras, J. K. Barstow, Jonathan J. Fortney, Peter Gao, Heather A. Knutson, Ryan J. MacDonald, T. M. Evans, Benjamin V. Rackham, Jake Taylor, Vivien Parmentier, Natalie M. Batalha, Zachory K. Berta-Thompson, Aarynn L. Carter, Quentin Changeat, Leonardo A. Dos Santos, Neale P. Gibson, Jayesh Goyal, Laura Kreidberg, Mercedes López‐Morales, Joshua D. Lothringer, Yamila Miguel, Karan Molaverdikhani, Sarah E. Moran, Giuseppe Morello, Sagnick Mukherjee, David K. Sing, Kevin B. Stevenson, Hannah R. Wakeford, Eva-Maria Ahrer, Munazza K. Alam, Lili Alderson, Natalie H. Allen, Natasha Batalha, Taylor J. Bell, Jasmina Blecic, Jonathan Brande, C. Cáceres, S. L. Casewell, K. L. Chubb, Ian J. M. Crossfield, Nicolas Crouzet, Patricio E. Cubillos, L. Decin, Jean-Michel Désert, Joseph Harrington, Kevin Heng, Thomas Henning, Nicolas Iro, Eliza M.-R. Kempton, Sarah Kendrew, James Kirk, Jessica Krick, Pierre-Olivier Lagage, M. Lendl, L. Mancini, Megan Mansfield, Erin May, N. J. Mayne, Nikolay Nikolov, Ε. Πάλλη, D. J. M. Petit dit de la Roche, Caroline Piaulet, Diana Powell, Seth Redfield, Laura K. Rogers, Michael T. Roman, Pierre-Alexis Roy, Matthew C. Nixon, Everett Schlawin, Xianyu Tan, Pascal Tremblin, Jake D. Turner, Olivia Vénot, William C. Waalkes, P. J. Wheatley, Xi Zhang
Abstract
Abstract The Saturn-mass exoplanet WASP-39b has been the subject of extensive efforts to determine its atmospheric properties using transmission spectroscopy 1–4 . However, these efforts have been hampered by modelling degeneracies between composition and cloud properties that are caused by limited data quality 5–9 . 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.