Silicate precursor silane detected in cold low-metallicity brown dwarf

Jacqueline K. Faherty (), Aaron M. Meisner, Ben Burningham, Channon Visscher, Michael Line, Genaro Suárez, Jonathan Gagné, Sherelyn Alejandro Merchan, Austin James Rothermich, Adam J. Burgasser, Adam C. Schneider, Dan Caselden, J. Davy Kirkpatrick, Marc Jason Kuchner, Daniella Carolina Bardalez Gagliuffi, Peter Eisenhardt, Christopher R. Gelino, Eileen C. Gonzales, Federico Marocco, Sandy Leggett, Nicolas Lodieu, Sarah L. Casewell, Pascal Tremblin, Michael Cushing, Maria Rosa Zapatero Osorio, Víctor J. S. Béjar, Bartosz Gauza, Edward Wright, Mark W. Phillips, Jun-Yan Zhang and Eduardo L. Martin
Additional contact information
Jacqueline K. Faherty: American Museum of Natural History
Aaron M. Meisner: NSF National Optical-Infrared Astronomy Research Laboratory
Ben Burningham: University of Hertfordshire
Channon Visscher: Dordt University
Michael Line: Arizona State University
Genaro Suárez: American Museum of Natural History
Jonathan Gagné: Planétarium de Montreal
Sherelyn Alejandro Merchan: American Museum of Natural History
Austin James Rothermich: American Museum of Natural History
Adam J. Burgasser: University of California, San Diego
Adam C. Schneider: United States Naval Observatory
Dan Caselden: American Museum of Natural History
J. Davy Kirkpatrick: Caltech
Marc Jason Kuchner: NASA
Daniella Carolina Bardalez Gagliuffi: Amherst College
Peter Eisenhardt: California Institute of Technology
Christopher R. Gelino: Caltech
Eileen C. Gonzales: San Francisco State University
Federico Marocco: Caltech
Sandy Leggett: Gemini Observatory
Nicolas Lodieu: Instituto de Astrofísica de Canarias
Sarah L. Casewell: University of Leicester
Pascal Tremblin: Université Paris-Saclay, UVSQ, CNRS, CEA
Michael Cushing: University of Toledo
Maria Rosa Zapatero Osorio: CSIC-INTA
Víctor J. S. Béjar: Instituto de Astrofísica de Canarias
Bartosz Gauza: University of Zielona Góra
Edward Wright: University of California, Los Angeles
Mark W. Phillips: University of Edinburgh
Jun-Yan Zhang: Instituto de Astrofísica de Canarias
Eduardo L. Martin: Instituto de Astrofísica de Canarias

Nature, 2025, vol. 645, issue 8079, 62-66

Abstract: 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. 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 μm 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.

Date: 2025
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DOI: 10.1038/s41586-025-09369-1

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