Failed Star Shakes Up a Phosphine Cocktail express
Brown dwarfs — 'failed stars' that couldn't ignite their nuclear furnace. More massive than planets but lighter than stars, they resemble giant atmospheric mixers: their interiors are hot, their upper layers relatively cool, and powerful currents shake this mixture. Using spectroscopy (breaking light into colors) on JWST, scientists detected phosphine in Wolf 1130C. This gas, known from Jupiter, turned out to be ten times more concentrated here than previously seen.
Curiously, on Earth this gas smells like decay, while the cosmic 'cocktail' mixes odorlessly. Now astronomers can use such chemical markers to more clearly distinguish exoplanet from brown dwarfs.
Original abstract
as written by the authors arXiv:2510.03916
The atmospheres of low-temperature brown dwarfs and gas giant planets are expected to contain the phosphine molecule, PH$$_3$$ However, previous observations have shown much lower abundances of this molecule than predicted by atmospheric chemistry models. We report JWST spectroscopic observations of phosphine in the atmosphere of the brown dwarf Wolf 1130C. Multiple absorption lines due to phosphine are detected around 4.3 $${\mu}$$m, from which we calculate a phosphine abundance of 0.100$$\pm$$0.009 parts per million. This abundance is consistent with disequilibrium atmospheric chemistry models that reproduce the phosphine abundances in Jupiter and Saturn, and is much higher than abundances previously reported for other brown dwarfs or exoplanets.
On Earth, phosphine is a companion of rotting swamps, while in space it's born in the depths and carried up by storms.