Silicate precursor silane detected in cold low-metallicity brown dwarf

• 成果类型: Article
• 署名作者: Faherty, Jacqueline K.; Meisner, Aaron M.; Burningham, Ben; Visscher, Channon; Line, Michael; Suarez, Genaro; Gagne, Jonathan; Alejandro Merchan, Sherelyn; Rothermich, Austin James; Burgasser, Adam J.; Schneider, Adam C.; Caselden, Dan; Kirkpatrick, J. Davy; Kuchner, Marc Jason; Bardalez Gagliuffi, Daniella Carolina; Eisenhardt, Peter; Gelino, Christopher R.; Gonzales, Eileen C.; Marocco, Federico; Leggett, Sandy; Lodieu, Nicolas; Casewell, Sarah L.; Tremblin, Pascal; Cushing, Michael; Zapatero Osorio, Maria Rosa; Bejar, Victor J. S.; Gauza, Bartosz; Wright, Edward; Phillips, Mark W.; Zhang, Jun-Yan; Martin, Eduardo L.
• 署名单位: American Museum of Natural History (AMNH); City University of New York (CUNY) System; University of Hertfordshire; Arizona State University; Arizona State University-Tempe; Universite de Montreal; University of California System; University of California San Diego; California Institute of Technology; National Aeronautics & Space Administration (NASA); Amherst College; National Aeronautics & Space Administration (NASA); NASA Jet Propulsion Laboratory (JPL); California Institute of Technology; California State University System; San Francisco State University; Instituto de Astrofisica de Canarias; Universidad de la Laguna; University of Leicester; Universite Paris Saclay; CEA; Centre National de la Recherche Scientifique (CNRS); University System of Ohio; University of Toledo; Consejo Superior de Investigaciones Cientificas (CSIC); CSIC - Centro de Astrobiologia (INTA); University of Zielona Gora; University of California System; University of California Los Angeles; University of Edinburgh
• 刊物名称: Nature
• ISSN/ISSBN: 0028-1305
• DOI: 10.1038/s41586-025-09369-1
• 发表日期: 2025-09-04
• 关键词: 20 pc census; atmospheric chemistry; giant planets; nitrogen; opacity; carbon; stars

摘要

Within 20 pc of the Sun, there are currently 29 known cold brown dwarfs-sources with measured distances and an estimated effective temperature between that of Jupiter (170 K) and approximately 500 K (ref. 1). These sources are almost all isolated and are the closest laboratories we have for detailed atmospheric studies of giant planets formed outside the Solar System. Here we report JWST observations of one such source, WISEA J153429.75-104303.3 (W1534), which we confirm is a substellar mass member of the Galactic halo with a metallicity of less than 0.01 times solar. Its spectrum reveals methane (CH4), water (H2O) and silane (SiH4) gas. Although SiH4 is expected to serve as a key reservoir for the cloud-forming element Si in gas giant worlds, it has remained undetected until now because it is removed from observable atmospheres by the formation of silicate clouds at depth. These condensates are favoured with increasing metallicity, explaining why SiH4 remains undetected on well-studied metal-rich Solar System worlds such as Jupiter and Saturn2. On the metal-poor world W1534, we detect a clear signature of SiH4 centred at about 4.55 mu m with an abundance of 19 +/- 2 parts per billion. Our chemical modelling suggests that this SiH4 abundance may be quenched at approximately kilobar levels just above the silicate cloud layers, in which vertical atmospheric mixing can transport SiH4 to the observable photosphere. The formation and detection of SiH4 demonstrates key coupled relationships between composition, cloud formation and atmospheric mixing in cold brown dwarf and planetary atmospheres.