Webb detects phosphine on 10-billion-year-old brown dwarf, but its origin remains unknown.

The James Webb Space Telescope has detected phosphine in the atmosphere of Wolf 1130C, a 10-billion-year-old brown dwarf 54 light-years away, marking the first clear sighting in a brown dwarf. The molecule’s presence, at about 100 parts per billion, matches theoretical predictions but contrasts with earlier non-detections in 23 other brown dwarfs, puzzling scientists. While phosphine was once considered a potential sign of alien life—especially after controversial claims about Venus—it also forms through non-biological processes in gas giants like Jupiter and Saturn. The discovery highlights that phosphine’s origin remains unclear across diverse celestial bodies, undermining its reliability as a biosignature. Researchers now stress that atmospheric chemistry in space is complex and that phosphine alone cannot confirm life.