Photochemically produced SO2 in the atmosphere of WASP-39b
Shang‐Min Tsai, Elspeth K. H. Lee, Diana Powell, Peter Gao, Xi Zhang, Julianne I. Moses, Éric Hébrard, Olivia Vénot, Vivien Parmentier, Sean Jordan, Renyu Hu, Munazza K. Alam, Lili Alderson, Natalie M. Batalha, Jacob L. Bean, Björn Benneke, C. J. Bierson, Ryan P. Brady, L. Carone, Aarynn L. Carter, K. L. Chubb, Julie Inglis, Jérémy Leconte, Michael Line, Mercedes López‐Morales, Yamila Miguel, Karan Molaverdikhani, Zafar Rustamkulov, David K. Sing, Kevin B. Stevenson, Hannah R. Wakeford, Jeehyun Yang, Keshav Aggarwal, Robin Baeyens, Saugata Barat, M. de Val-Borro, Tansu Daylan, Jonathan J. Fortney, Kevin France, Jayesh Goyal, David Grant, James Kirk, Laura Kreidberg, Amy Louca, Sarah E. Moran, Sagnick Mukherjee, E. Nasedkin, Kazumasa Ohno, Benjamin V. Rackham, Seth Redfield, Jake Taylor, Pascal Tremblin, Channon Visscher, Nicole L. Wallack, Luis Welbanks, Allison Youngblood, Eva-Maria Ahrer, Natasha E. Batalha, Patrick Behr, Zachory K. Berta-Thompson, Jasmina Blecic, S. L. Casewell, Ian J. M. Crossfield, Nicolas Crouzet, Patricio E. Cubillos, L. Decin, Jean-Michel Désert, Adina D. Feinstein, Neale P. Gibson, Joseph Harrington, Kevin Heng, Thomas Henning, Eliza M.-R. Kempton, Jessica Krick, Pierre-Olivier Lagage, M. Lendl, Joshua D. Lothringer, Megan Mansfield, N. J. Mayne, T. M. Evans, Ε. Πάλλη, Everett Schlawin, Oliver Shorttle, P. J. Wheatley, S. N. Yurchenko
Abstract
Abstract Photochemistry is a fundamental process of planetary atmospheres that regulates the atmospheric composition and stability 1 . However, no unambiguous photochemical products have been detected in exoplanet atmospheres so far. Recent observations from the JWST Transiting Exoplanet Community Early Release Science Program 2,3 found a spectral absorption feature at 4.05 μm arising from sulfur dioxide (SO 2 ) in the atmosphere of WASP-39b. WASP-39b is a 1.27-Jupiter-radii, Saturn-mass (0.28 M J ) gas giant exoplanet orbiting a Sun-like star with an equilibrium temperature of around 1,100 K (ref. 4 ). The most plausible way of generating SO 2 in such an atmosphere is through photochemical processes 5,6 . Here we show that the SO 2 distribution computed by a suite of photochemical models robustly explains the 4.05-μm spectral feature identified by JWST transmission observations 7 with NIRSpec PRISM (2.7 σ ) 8 and G395H (4.5 σ ) 9 . SO 2 is produced by successive oxidation of sulfur radicals freed when hydrogen sulfide (H 2 S) is destroyed. The sensitivity of the SO 2 feature to the enrichment of the atmosphere by heavy elements (metallicity) suggests that it can be used as a tracer of atmospheric properties, with WASP-39b exhibiting an inferred metallicity of about 10× solar. We further point out that SO 2 also shows observable features at ultraviolet and thermal infrared wavelengths not available from the existing observations.