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

Adina D. Feinstein, Michael Radica, Luis Welbanks, Catriona Anne Murray, Kazumasa Ohno, Louis Philippe Coulombe, Néstor Espinoza, Jacob L. Bean, Johanna K. Teske, Björn Benneke, Michael R. Line, Zafar Rustamkulov, Arianna Saba, Angelos Tsiaras, Joanna K. Barstow, Jonathan J. Fortney, Peter Gao, Heather A. Knutson, Ryan J. MacDonald, Thomas Mikal-EvansBenjamin 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 M. 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 E. Batalha, Taylor J. Bell, Jasmina Blecic, Jonathan Brande, Claudio Caceres, S. L. Casewell, Katy L. Chubb, Ian J.M. Crossfield, Nicolas Crouzet, Patricio E. Cubillos, Leen 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, Monika Lendl, Luigi Mancini, Megan Mansfield, E. M. May, N. J. Mayne, Nikolay K. Nikolov, Enric Palle, Dominique 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, P. Tremblin, Jake D. Turner, Olivia Venot, William C. Waalkes, Peter J. Wheatley, Xi Zhang

Research output: Contribution to journalArticlepeer-review

72 Scopus citations


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.

Original languageEnglish (US)
Pages (from-to)670-675
Number of pages6
Issue number7949
StatePublished - Feb 23 2023

ASJC Scopus subject areas

  • General


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