Webb Finds Phosphorus-Bearing Gas in an Ancient Brown Dwarf

The James Webb Space Telescope has been used to find the presence of phosphine (PH₃) in the atmosphere of Wolf 1130C. The brown dwarf Wolf 1130C is 54 light-years away in Cygnus, in a triple-star system. It is very metal-poor, i.e., it has much less heavy elements than the Sun, and as a consequence, it is a natural laboratory of primitive chemistry. The discovery of the gas containing phosphorus in this case is especially remarkable and surprising.

Discovery in an Unlikely Atmosphere

According to the recent study, Wolf 1130C orbits a red dwarf and a white dwarf in the triple-star system Wolf 1130ABC. It is an ancient, very metal-poor brown dwarf –a so-called “failed star” that cannot sustain hydrogen fusion. Using JWST's infrared spectrum, researchers detected phosphine (PH₃) in its atmosphere and confirmed it with atmospheric retrieval models. This was unexpected: PH₃ forms naturally in hydrogen-rich gas giants and was predicted in brown dwarfs, yet all previous JWST surveys of similar objects found none.

Rethinking Phosphorus Chemistry in Space

One of the hypotheses is that Wolf 1130C has such a low level of oxygen in its atmosphere that phosphorus cannot oxidise, but remains bound to hydrogen as phosphine. As an alternative, the phosphorus concentration of the system might have been enhanced by its white dwarf companion: white dwarfs, which have gone nova, can synthesise heavy elements, and previous outbursts may have deposited additional phosphorus around Wolf 1130C. Such possibilities imply that we may have to revise our knowledge of phosphorus chemistry in space. Burgasser cautions that phosphine cannot be regarded as a certainty of life until scientists can answer the question of why it should be there on this dead world.