Early Release Science of the Exoplanet WASP-39b with JWST NIRSpec G395H

Alderson, Lili; Wakeford, Hannah R; Alam, Munazza K; Batalha, Natasha E; Lothringer, Joshua D; Redai, Jea Adams; Barat, Saugata; Brande, Jonathan; Damiano, Mario; Daylan, Tansu; Espinoza, Néstor; Flagg, Laura; Goyal, Jayesh M; Grant, David; Hu, Renyu; Inglis, Julie; Lee, Elspeth K H; Mikal-Evans, Thomas; Ramos-Rosado, Lakeisha; Roy, Pierre-Alexis; Wallack, Nicole L; Batalha, Natalie M; Bean, Jacob L; Benneke, Björn; Berta-Thompson, Zachory K; Carter, Aarynn L; Changeat, Quentin; Colón, Knicole D; Crossfield, Ian J M; Désert, Jean-Michel; Foreman-Mackey, Daniel; Gibson, Neale P; Kreidberg, Laura; Line, Michael R; López-Morales, Mercedes; Molaverdikhani, Karan; Moran, Sarah E; Morello, Giuseppe; Moses, Julianne I; Mukherjee, Sagnick; Schlawin, Everett; Sing, David K; Stevenson, Kevin B; Taylor, Jake; Aggarwal, Keshav; Ahrer, Eva-Maria; Allen, Natalie H; Barstow, Joanna K.; Bell, Taylor J; Blecic, Jasmina; Casewell, Sarah L; Chubb, Katy L; Crouzet, Nicolas; Cubillos, Patricio E; Decin, Leen; Feinstein, Adina D; Fortney, Joanthan J; Harrington, Joseph; Heng, Kevin; Iro, Nicolas; Kempton, Eliza M-R; Kirk, James; Knutson, Heather A; Krick, Jessica; Leconte, Jérémy; Lendl, Monika; MacDonald, Ryan J; Mancini, Luigi; Mansfield, Megan; May, Erin M; Mayne, Nathan J; Miguel, Yamila; Nikolov, Nikolay K; Ohno, Kazumasa; Palle, Enric; Parmentier, Vivien; Petit Dit de la Roche, Dominique J M; Piaulet, Caroline; Powell, Diana; Rackham, Benjamin V; Redfield, Seth; Rogers, Laura K; Rustamkulov, Zafar; Tan, Xianyu; Tremblin, P; Tsai, Shang-Min; Turner, Jake D; de Val-Borro, Miguel; Venot, Olivia; Welbanks, Luis; Wheatley, Peter J and Zhang, Xi (2023). Early Release Science of the Exoplanet WASP-39b with JWST NIRSpec G395H. Nature, 614 pp. 664–669.

DOI: https://doi.org/10.1038/s41586-022-05591-3

Abstract

Measuring the abundances of carbon and oxygen in exoplanet atmospheres is considered a crucial avenue for unlocking the formation and evolution of exoplanetary systems^1,2. Access to an exoplanet's chemical inventory requires high precision observations, often inferred from individual molecular detections with low-resolution space-based^3-5 and high-resolution ground-based^6-8 facilities. Here we report the medium-resolution (R≈600) transmission spectrum of an exoplanet atmosphere between 3-5 μm covering multiple absorption features for the Saturn-mass exoplanet WASP-39^b obtained with JWST NIRSpec G395H. Our observations achieve 1.46 X photon precision, providing an average transit depth uncertainty of 221 ppm per spectroscopic bin, and present minimal impacts from systematic effects. We detect significant absorption from CO (28.5σ) and H O (21.5σ), and identify SO₂ as the source of absorption at 4.1µm (4.8σ). Best-fit atmospheric models range between 3 X and 10 X solar metallicity, with sub-solar to solar C/O ratios. These results, including the detection of SO₂, underscore the importance of characterising the chemistry in exoplanet atmospheres, and showcase NIRSpec G395H as an excellent mode for time series observations over this critical wavelength range¹⁰.