Methane emission from a cool brown dwarf

• 成果类型: Article
• 署名作者: Faherty, Jacqueline K.; Burningham, Ben; Gagne, Jonathan; Suarez, Genaro; Vos, Johanna M.; Merchan, Sherelyn Alejandro; Morley, Caroline V.; Rowland, Melanie; Lacy, Brianna; Kiman, Rocio; Caselden, Dan; Kirkpatrick, J. Davy; Meisner, Aaron; Schneider, Adam C.; Kuchner, Marc Jason; Gagliuffi, Daniella Carolina Bardalez; Beichman, Charles; Eisenhardt, Peter; Gelino, Christopher R.; Gharib-Nezhad, Ehsan; Gonzales, Eileen; Marocco, Federico; Rothermich, Austin James; Whiteford, Niall
• 署名单位: American Museum of Natural History (AMNH); University of Hertfordshire; Universite de Montreal; Trinity College Dublin; City University of New York (CUNY) System; Hunter College (CUNY); University of Texas System; University of Texas Austin; California Institute of Technology; California Institute of Technology; National Aeronautics & Space Administration (NASA); NASA Goddard Space Flight Center; Amherst College; California Institute of Technology; National Aeronautics & Space Administration (NASA); NASA Jet Propulsion Laboratory (JPL); National Aeronautics & Space Administration (NASA); NASA Ames Research Center; California State University System; San Francisco State University; Cornell University; Cornell University
• 刊物名称: Nature
• ISSN/ISSBN: 0028-4294
• DOI: 10.1038/s41586-024-07190-w
• 发表日期: 2024-04-18
• 页码: 511-+
• 关键词: free absorption-coefficient; thermal structure; atmosphere; uranus; ion

摘要

Beyond our Solar System, aurorae have been inferred from radio observations of isolated brown dwarfs(1,2). Within our Solar System, giant planets have auroral emission with signatures across the electromagnetic spectrum including infrared emission of H-3(+) and methane. Isolated brown dwarfs with auroral signatures in the radio have been searched for corresponding infrared features, but only null detections have been reported(3). CWISEP J193518.59-154620.3. (W1935 for short) is an isolated brown dwarf with a temperature of approximately 482K. Here we report James Webb Space Telescope observations of strong methane emission from W1935 at 3.326 mu m. Atmospheric modelling leads us to conclude that a temperature inversion of approximately 300K centred at 1-10mbar replicates the feature. This represents an atmospheric temperature inversion for a Jupiter-like atmosphere without irradiation from a host star. A plausible explanation for the strong inversion is heating by auroral processes, although other internal and external dynamical processes cannot be ruled out. The best-fitting model rules out the contribution of H-3(+) emission, which is prominent in Solar System gas giants. However, this is consistent with rapid destruction of H-3(+) at the higher pressure where the W1935 emission originates(4).