Astronomers utilizing the NASA/ESA/CSA James Webb Space Telescope have identified phosphine (PH)₃ in the atmosphere of the brown dwarf Wolf 1130c, part of the triple system 1130ABC.

Wolf 1130ABC is located approximately 54 light years away in the constellation Cygnus.

The system is also known for LHS 482, Gliese 781, and Ross 1069b. It consists of three components: the Cool Red Star Wolf 1130a, the massive white dwarf Wolf 1130b, and the brown dwarf Wolf 1130c.

Initially discovered in 2013, Wolf 1130c orbits the closely bound systems of Wolf 1130a and Wolf 1130b on a wide trajectory.

“The astronomical initiative known as the Ancient Arcana concentrates on ancient, metal-rich brown dwarfs to enhance our understanding of atmospheric chemistry,” stated Adam Burgasser, a professor at the University of California, San Diego.

“Identifying phosphine was one of our primary objectives.”

Phosphine naturally emerges in the hydrogen-dominated atmospheres of gas giants like Jupiter and Saturn.

This has led scientists to theorize that phosphine should exist in the atmospheres of exoplanetary gas giants as well.

Nevertheless, previous Webb observations often failed to detect phosphines, pointing to an incomplete understanding of phosphorus chemistry.

“Before Webb, the expectation was that phosphine would be plentiful in planetary and brown dwarf atmospheres, according to theoretical models based on the turbulent mixing in these environments.”

Wolf 1130c is of particular interest to brown dwarf astronomers due to its lower concentration of “metals” (elements beyond hydrogen and helium) compared to the Sun.

In contrast to other brown dwarfs, the team successfully detected phosphines in the infrared spectral data collected by Webb from Wolf 1130c.

To accurately interpret their findings, researchers needed to ascertain the abundance of this gas within the atmosphere of Wolf 1130c.

“We employed a modeling approach called atmospheric recovery to quantify the molecular constituents of Wolf 1130c,” explained Dr. Irene Gonzalez from San Francisco State University.

“This technique leverages Webb’s data to validate the expected presence of various molecular gas species in the atmosphere.”

“It’s akin to reverse-engineering a delicious cookie when a chef remains committed to a recipe.”

“Typically, phosphorus may bond with other molecules, such as phosphorus trioxide,” remarked Dr. Baylor.

“In the metal-poor atmosphere of Wolf 1130c, insufficient oxygen prevents phosphorus from forming this way, allowing it to arise from phosphine-rich hydrogen.”

Alternatively, the phosphine could have been synthesized locally within the Wolf 1130ABC system, particularly from the white dwarf Wolf 1130b.

“The white dwarf represents the remnant shell of a star that has completed hydrogen fusion,” Professor Burgasser explained.

“These stars are incredibly dense and can accumulate material on their surfaces, potentially spurring runaway nuclear reactions.”

While astronomers have not observed such phenomena in the Wolf 1130ABC system in recent history, nova events usually cycle every thousands to tens of thousands of years.

This system has been recognized for just a century, and earlier invisible explosions may have contributed to a legacy of phosphorus contamination.

Gaining insights into why this particular brown dwarf exhibits a distinct signature of phosphine could shed new light on phosphorus synthesis in the Milky Way and atmospheric chemistry on exoplanets.

“If we aim to use this molecule in the quest for life in terrestrial worlds outside our solar system, understanding the atmospheric phosphine chemistry of brown dwarfs becomes crucial,” Professor Burgasser commented.

This study will be published in the journal Science.

____

Adam J. Burgasser et al. Observation of unexpected phosphines in the atmosphere of the cold brown dwarf. Science. Released online on October 2, 2025. doi:10.1126/science.adu0401