A secondary atmosphere on the rocky exoplanet 55 Cancri e

• 成果类型: Article
• 署名作者: Hu, Renyu; Bello-Arufe, Aaron; Zhang, Michael; Paragas, Kimberly; Zilinskas, Mantas; van Buchem, Christiaan; Bess, Michael; Patel, Jayshil; Ito, Yuichi; Damiano, Mario; Scheucher, Markus; Oza, Apurva V.; Knutson, Heather A.; Miguel, Yamila; Dragomir, Diana; Brandeker, Alexis; Demory, Brice-Olivier
• 署名单位: California Institute of Technology; National Aeronautics & Space Administration (NASA); NASA Jet Propulsion Laboratory (JPL); California Institute of Technology; University of Chicago; Leiden University - Excl LUMC; Leiden University; University of New Mexico; Stockholm University; National Institutes of Natural Sciences (NINS) - Japan; National Astronomical Observatory of Japan (NAOJ); University of London; University College London; University of Bern; University of Bern
• 刊物名称: Nature
• ISSN/ISSBN: 0028-5056
• DOI: 10.1038/s41586-024-07432-x
• 发表日期: 2024-06-20
• 关键词: mass fractionation; earth; chemistry; MODEL; planetary; curve

摘要

Characterizing rocky exoplanets is a central aim of astronomy, and yet the search for atmospheres on rocky exoplanets has so far resulted in either tight upper limits on the atmospheric mass1-3 or inconclusive results4-6. The 1.95REarth and 8.8MEarth planet 55 Cancri e (abbreviated 55 Cnc e), with a predominantly rocky composition and an equilibrium temperature of around 2,000 K, may have a volatile envelope (containing molecules made from a combination of C, H, O, N, S and P elements) that accounts for up to a few percent of its radius7-13. The planet has been observed extensively with transmission spectroscopy14-22 and its thermal emission has been measured in broad photometric bands23-26. These observations disfavour a primordial H2/He-dominated atmosphere but cannot conclusively determine whether the planet has a secondary atmosphere27,28. Here we report a thermal emission spectrum of the planet obtained by the NIRCam and MIRI instruments aboard the James Webb Space Telescope (JWST) from 4 to 12 mu m. The measurements rule out the scenario in which the planet is a lava world shrouded by a tenuous atmosphere made of vaporized rock29-32 and indicate a bona fide volatile atmosphere that is probably rich in CO2 or CO. This atmosphere can be outgassed from and sustained by a magma ocean. The thermal emission spectrum of the rocky exoplanet 55 Cancri e obtained by the NIRCAM and MIRI instruments aboard the JWST indicates that it has a secondary volatile-rich atmosphere, possibly arising from a magma ocean.