What is Astrochemistry?

Abstract

We define what we mean by astrochemistry: it is the study of the chemistry that occurs in interstellar and circumstellar space in galaxies, including star- and planet-forming regions. We give a brief historical survey of how the subject began and how it has developed. We describe the conditions of the gas in interstellar space of the Milky Way, and discuss briefly the presence and nature of interstellar dust. The important transfer of matter from interstellar space into stars and planets, and from stars to space, is outlined. Gas densities and temperatures in astrochemistry are very different from terrestrial values and fluxes of radiation seem to imply that interstellar regions are apparently hostile to chemistry. Yet a rich chemistry has been discovered in interstellar and circumstellar space: a table of detected species is provided. The chapter ends with a list of questions, mainly dealing with the fundamental question: can we devise a special chemistry operating in these apparently hostile environments that is able to generate the range of molecules that are detected?