Interstellar comet 3I/ATLAS reveals outer-disk isotopic fingerprints
Astronomers measuring CN isotopologues in the interstellar comet 3I/ATLAS find unusually high 12C/13C (~151) and 14N/15N (~363) ratios, higher than Solar System comets and closer to interstellar/outer-disk values, implying 3I formed in the outer disk around an old, low-metallicity star and offering rare clues about planetesimal formation under different stellar environments.