Silicate precursor silane detected in cold low-metallicity brown dwarf

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. <sup>1</sup>). 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 (CH<sub>4</sub>), water (H<sub>2</sub>O) and silane (SiH<sub>4</sub>) gas. Although SiH<sub>4</sub> 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 SiH<sub>4</sub> remains undetected on well-studied metal-rich Solar System worlds such as Jupiter and Saturn<sup>2</sup>. On the metal-poor world W1534, we detect a clear signature of SiH<sub>4</sub> centred at about 4.55 μm with an abundance of 19 ± 2 parts per billion. Our chemical modelling suggests that this SiH<sub>4</sub> abundance may be quenched at approximately kilobar levels just above the silicate cloud layers, in which vertical atmospheric mixing can transport SiH<sub>4</sub> to the observable photosphere. The formation and detection of SiH<sub>4</sub> demonstrates key coupled relationships between composition, cloud formation and atmospheric mixing in cold brown dwarf and planetary atmospheres.

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Nature
Published
2025-08-20
DOI
https://doi.org/10.1038/s41586-025-09369-1
Citations
3
Primary Topic
Stellar, planetary, and galactic studies
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article
Field-Weighted Citation Impact
3.46
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article

Silicate precursor silane detected in cold low-metallicity brown dwarf

Adam C. Schneider, Jacqueline K. Faherty, Christopher R. Gelino, S. K. Leggett et al.
3 citations
Nature
Stellar, planetary, and galactic studies
3.46
article

Silicate precursor silane detected in cold low-metallicity brown dwarf

Adam C. Schneider, Jacqueline K. Faherty, Christopher R. Gelino, S. K. Leggett, Dan Caselden, M. R. Zapatero Osorio, Adam J. Burgasser, Pascal Tremblin, Channon Visscher, S. L. Casewell, J. Davy Kirkpatrick, Peter Eisenhardt, Federico Marocco, Jonathan Gagné, V. J. S. Béjar, Ben Burningham, M. W. Phillips, Genaro Suárez, B. Gauza, Austin Rothermich, J.-Y. Zhang, Michael C. Cushing, E. L. Wright, Aaron Meisner, Michael Line, Sherelyn Alejandro Merchan, Eileen C. Gonzales, N. Lodieu, E. L. Martı́n, Marc J. Kuchner, Daniella Carolina Bardalez Gagliuffi
article en
3 citations

Abstract

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. <sup>1</sup>). 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 (CH<sub>4</sub>), water (H<sub>2</sub>O) and silane (SiH<sub>4</sub>) gas. Although SiH<sub>4</sub> 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 SiH<sub>4</sub> remains undetected on well-studied metal-rich Solar System worlds such as Jupiter and Saturn<sup>2</sup>. On the metal-poor world W1534, we detect a clear signature of SiH<sub>4</sub> centred at about 4.55 μm with an abundance of 19 ± 2 parts per billion. Our chemical modelling suggests that this SiH<sub>4</sub> abundance may be quenched at approximately kilobar levels just above the silicate cloud layers, in which vertical atmospheric mixing can transport SiH<sub>4</sub> to the observable photosphere. The formation and detection of SiH<sub>4</sub> demonstrates key coupled relationships between composition, cloud formation and atmospheric mixing in cold brown dwarf and planetary atmospheres.

NatureVol. 645(8079)
The Graduate Center, CUNY (US), California Institute of Technology (US), Centre National de la Recherche Scientifique (FR), Space Science Institute (US), Jet Propulsion Laboratory (US), American Museum of Natural History (US), University of Hertfordshire (GB), Dordt University (US), University of Leicester (GB), Universidad de La Laguna (ES), University of California, Los Angeles (US), City University of New York (US), Amherst College (US), Université de Versailles Saint-Quentin-en-Yvelines (FR), Commissariat à l'Énergie Atomique et aux Énergies Alternatives (FR), Université Paris-Saclay (FR), Espace pour la vie (CA), University of California San Diego (US), Gemini North Observatory (US), Maison de la Simulation (FR), CEA Paris-Saclay (FR), Centro de Astrobiología (ES), Instituto de Astrofísica de Canarias (ES), NSF NOIRLab (US), United States Naval Observatory (US), Infrared Processing and Analysis Center (US), University of Zielona Góra (PL), UK Astronomy Technology Centre (GB), Arizona State University (US), Université de Montréal (CA), San Francisco State University (US), University of Toledo (US), University of Edinburgh (GB)
Openalex Percentile: Top 7%
Stellar, planetary, and galactic studies
3.46
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