H-3(+) IN SPACE

H-3+, the simplest triatomic molecule, has been the subject of a great deal of interest by laboratory spectroscopists and theoretical chemists. In the past few years, however, it has taken on a new importance as an astronomical probe, following its detection in the atmosphere of Jupiter. This article explains some of the challenges posed by H-3+ to spectroscopists and theorists alike and shows how it has given infrared astronomers a new insight into planetary atmospheres. Conditions for detecting H-3+ in the interstellar medium - the vast gas clouds that lie between the stars - are also discussed.