JWST Detects First-Ever 'Forbidden' Signal from Key Molecule in Distant Gas

The James Webb Space Telescope has detected a never-before-seen "forbidden" light signal from the trihydrogen cation (H3+), a molecule crucial for interstellar chemistry, in gas thousands of light-years away. This marks the first observation of a rotational emission predicted since 1986, which had eluded all previous lab and telescope searches. The signal was found in the Herbig-Haro object HH 168, where shock waves from a newborn star's jets heat surrounding gas. The team identified 26 distinct spectral lines matching the predicted faint rotational transitions, with the strongest showing a 72-sigma confidence level, leaving virtually no doubt about the detection. The emission's brightness exceeded model predictions, and similar signals were also found in another object, HH 211. This discovery could help scientists understand shock wave physics and use H3+ as a tool to study how the universe's simplest element forms complex organic molecules.