title: Observational astrochemistry.
abstract: Astronomers have identified some 70 molecular species in dense interstellar clouds and the envelopes expelled by evolved stars.  Some 75% of these are organic, including molecules with up to 13 atoms and with weights up to 147 daltons.  Elements found in interstellar compounds include H, C, N, O, S, Si, and probably Cl.  A recent addition to the list of interstellar molecules is the first hydrocarbon ring, cyclopropenylidene (C3H2).  Current research in astrochemistry is concentrating on the determination of accurate chemical abundances as a function of environment.  Both basic similarities and intriguing differences among clouds are found, which may provide clues to processes associated with cloud evolution and star formation.
authors.affiliation: Five College Radio Astronomy Observatory, University of Massachusetts, Amherst 01003, USA.
authors.forename: W M
authors.initials: WM
authors.lastname: Irvine
authors.forename: A
authors.initials: A
authors.lastname: Hjalmarson
mesh_terms: D055580:Astronomical Phenomena; D001256:Astronomy; D055598:Chemical Phenomena; D002621:Chemistry; D004602:Elements; D005118:Extraterrestrial Environment; D005740:Gases / Q000032:analysis; D006838:Hydrocarbons / Q000032:analysis* / Q000737:chemistry
chemical_list: D004602:Elements; D005740:Gases; D006838:Hydrocarbons