Authors: Lili Alderson | Hannah R. Wakeford | Munazza K. Alam | Natasha Batalha | Joshua D. Lothringer | Jéa Adams Redai | Saugata Barat | Jonathan Brande | Mario Damiano | Tansu Daylan | Néstor Espinoza | Laura Flagg | Jayesh Goyal | David Grant | Renyu Hu | Julie Inglis | Elspeth K. H. Lee | T. M. Evans | Lakeisha Ramos-Rosado | Pierre-Alexis Roy | Nicole L. Wallack | Natalie M. Batalha | Jacob L. Bean | Björn Benneke | Zachory K. Berta-Thompson | Aarynn L. Carter | Quentin Changeat | Knicole D. Colón | Ian J. M. Crossfield | Jean-Michel Désert | Daniel Foreman-Mackey | Neale P. Gibson | Laura Kreidberg | Michael Line | Mercedes López‐Morales | Karan Molaverdikhani | Sarah E. Moran | Giuseppe Morello | Julianne I. Moses | Sagnick Mukherjee | Everett Schlawin | David K. Sing | Kevin B. Stevenson | Jake Taylor | Keshav Aggarwal | Eva-Maria Ahrer | Natalie H. Allen | J. K. Barstow | Taylor J. Bell | Jasmina Blecic | S. L. Casewell | K. L. Chubb | Nicolas Crouzet | Patricio E. Cubillos | L. Decin | Adina D. Feinstein | Joanthan J. Fortney | Joseph Harrington | Kevin Heng | Nicolas Iro | Eliza M.-R. Kempton | James Kirk | Heather A. Knutson | Jessica Krick | Jérémy Leconte | M. Lendl | Ryan J. MacDonald | L. Mancini | Megan Mansfield | Erin May | Nathan J. Mayne | Yamila Miguel | Nikolay Nikolov | Kazumasa Ohno | Ε. Πάλλη | Vivien Parmentier | D. J. M. Petit dit de la Roche | Caroline Piaulet | Diana Powell | Benjamin V. Rackham | Seth Redfield | Laura K. Rogers | Zafar Rustamkulov | Xianyu Tan | Pascal Tremblin | Shang‐Min Tsai | Jake D. Turner | M. de Val-Borro | Olivia Vénot | Luis Welbanks | P. J. Wheatley | Xi Zhang
Source: Nature (article, 2023-01-09)
Field: Chemistry — Spectroscopy

Early Release Science of the exoplanet WASP-39b with JWST NIRSpec G395H Measuring the abundances of carbon and oxygen in exoplanet atmospheres is considered a crucial avenue for unlocking the formation and evolution of exoplanetary systems<sup>1,2</sup>. Access to the chemical inventory of an exoplanet requires high-precision observations, often inferred from individual molecular detections with low-resolution space-based<sup>3-5</sup> and high-resolution ground-based<sup>6-8</sup> facilities. Here we report the medium-resolution (R ≈ 600) transmission spectrum of an exoplanet atmosphere between 3 and 5 μm covering several absorption features for the Saturn-mass exoplanet WASP-39b (ref. <sup>9</sup>), obtained with the Near Infrared Spectrograph (NIRSpec) G395H grating of JWST. Our observations achieve 1.46 times 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<sub>2</sub> (28.5σ) and H<sub>2</sub>O (21.5σ), and identify SO<sub>2</sub> as the source of absorption at 4.1 μm (4.8σ). Best-fit atmospheric models range between 3 and 10 times solar metallicity, with sub-solar to solar C/O ratios. These results, including the detection of SO<sub>2</sub>, underscore the importance of characterizing the chemistry in exoplanet atmospheres and showcase NIRSpec G395H as an excellent mode for time-series observations over this critical wavelength range<sup>10</sup>. Exoplanet ; Transit (satellite) ; Spectrograph ; Absorption (acoustics) ; Metallicity ; Physics ; Atmosphere (unit) ; Astrophysics ; Planet ; Astronomy ; Astrobiology ; Spectral line ; Optics ; Stars ; Meteorology Spectroscopy and Laser Applications ; Astro and Planetary Science ; Atmospheric Ozone and Climate