Utilizing data gathered by NSF’s Gemini South Telescope and NASA/ESA/CSA James Webb Space Telescope, astronomers have identified methane signatures (CH4), water (H2O), and silane (SiH4) in the cold brown dwarf gas WISEA J153429.75-104303.3 (shortened to W1534). Silanes are predicted to act as significant reservoirs of silicon, the element responsible for the large clouds of gas that surround giant worlds, but their presence had remained undetected until now, masked by the development of deep silicate clouds in the observable atmosphere.
This artist’s illustration depicts a brown dwarf with an atmosphere filled with gas and dust clouds. Image credits: Noirlab/NSF/Aura/R. Proctor.
The W1534, referred to as the accident, is situated approximately 50 light years from Earth in the Libra constellation.
This brown dwarf was likely formed between 100 and 120 billion years ago and ranks among the oldest brown dwarfs discovered to date.
First identified in 2020 by citizen scientists participating in the Backyard Worlds: Planet 9 Citizen Science Project, its unusual light profile captivated astronomers.
Using two of the world’s most advanced terrestrial and space-based telescopes, astronomers examined its atmosphere to analyze its properties and composition.
The survey commenced with NSF’s Noirlab Astronomer Sandy Leggett capturing near-infrared images of W1534 with a Gemini South telescope in Chile, part of the International Gemini Observatory.
This initial work laid the groundwork for further explorations using Webb, guided by Noirlab Astronomer Aaron Meisner.
“W1534 is quite faint, and Gemini South is the only ground-based telescope capable of detecting it,” Dr. Meisner stated.
“The Gemini discovery paved the way for Webb’s observations by revealing the deeper atmospheric layers of this mysterious object and enabling us to determine the exposure time necessary to gather useful near-infrared data on its composition.”
Within W1534’s atmosphere, the team uncovered the crucial signature of silane, a compound formed from silicon and four hydrogen atoms.
Planetary scientists have long theorized the existence of this molecule within gas giants, attributing potential significance to its role in cloud formation within the atmosphere.
Despite extensive searches, its atmospheric presence has remained elusive in our solar system’s gas giants, Jupiter and Saturn, although thousands of studies on brown dwarfs and gas giants orbiting other stars have occurred.
This marks the first discovery of silanes in any brown dwarf, exoplanet, or solar system object.
The absence of this molecule in all but one singular brown dwarf suggests intriguing insights into the chemistry occurring in such an ancient environment.
“Often, it is these extreme objects that help us understand the average,” remarked Dr. Jackie Faherty, a researcher at the American Museum of Natural History.
The presence of silanes in W1534’s atmosphere implies that in very ancient objects, silicon is capable of bonding with hydrogen to form lighter molecules that can ascend to the upper layers of a gas giant’s atmosphere.
In contrast, more recently formed objects, such as Jupiter and Saturn, result in silicon bonding with readily available oxygen, producing heavier molecules that settle deeper into the atmospheric layers.
The evidence gleaned from W1534’s atmosphere further validates astronomers’ comprehension of gas giant cloud formation and sheds light on how primitive conditions influence atmospheric composition.
Moreover, it indicates that worlds formed billions of years ago display characteristics distinctly different from those formed during the early solar system.
“The formation and detection of silanes highlight an essential relationship among composition, cloud formation, and atmospheric mingling in cold brown dwarfs and planetary atmospheres,” the authors concluded.
Their paper is published in the journal Nature.
____
jk faherty et al. 2025. A silicate precursor silane detected in cold, low-metallic brown dwarfs. Nature 645, 62-66; doi:10.1038/s41586-025-09369-1
Source: www.sci.news
