Astronomers were astonished to find an abundance of phosphine, a molecule produced by microbes on Earth, in the atmosphere of a brown dwarf, an unusual type of object that lives in the grey zone between a giant planet and a tiny star.
As detailed in a new paper published in the journal Science, astronomers said they had found “undepleted phosphine,” a molecule made up of three hydrogen atoms and one phosphorus atom, in the atmosphere of Wolf 1130C, a brown dwarf 54 light-years from Earth.
The team, led by San Francisco State University astrophysicist Eileen Gonzales, analyzed data obtained by NASA’s James Webb Space Telescope and found that phosphine at a concentration of 100 parts per billion, far higher than previous observations of other brown dwarfs, as the New York Times reports.
On Earth, phosphine is a byproduct of decaying organic matter and one of six key elements necessary for life. It’s extremely rare beyond our planet, making it a promising target in our search for extraterrestrial life.
The molecule made headlines in 2020, in fact, when a team of researchers announced they had discovered a significant source of the stuff in the clouds above Venus, which triggered a years-long scientific debate about the possibility of life in the planet’s atmosphere.
As such, the latest findings surprised researchers.
“Prior to JWST, phosphine was expected to be abundant in exoplanet and brown dwarf atmospheres, following theoretical predictions based on the turbulent mixing we know exists in these sources,” as Trinity College Dublin postdoctoral scholar and coauthor Sam Beiler explained in a press release.
Yet until now, phosphine had mostly eluded detection, indicating gaps in our knowledge.
“My first impression was shock that we finally saw it,” Gonzales told the NYT. “We’ve been looking for so long.”
Wolf 1130C is older than conventional brown stars and has long depleted its sources of heavier elements, including oxygen, making it an even more unusual find.
The researchers were presented with a conundrum: why was Wolf 1130C so abundant in the stuff — while most other brown dwarfs lacked it entirely?
The team suggests that a white dwarf in its vicinity, Wolf 1130B, may have generated phosphorus on its surface as it accreted material. This process releases “runaway nuclear reactions, which we detect as novae,” as lead author and University of California, San Diego, professor Adam Burgasser explained in the press release.
However, to conclude that Wolf 1130C could be habitable would be jumping to conclusions. Instead, there’s a far more pertinent takeaway.
“Understanding phosphine chemistry in the atmospheres of brown dwarfs where we don’t expect life is crucial if we hope to use this molecule in the search for life on terrestrial worlds beyond our solar system,” Burgasser said.
More on brown dwarfs: James Webb Spots Mysterious Object Crossing Space Between Stars