The investigation of stars, star clusters and nebulae in 'Abd al-Rahman al-Ѕūfī’s book of the fixed stars

Abstract

Abd al-Rahmān al-Sūfī (AD 903–986) is justly famous for his Book of the Fixed Stars. This is an outstanding Medieval treatise on astronomy that was written in AD 964. This work was developed from Ptolemy’s Almagest, but was based upon al-Sūfī’s own stellar observations. The Book of the Fixed Stars has been copied down through the ages, and currently 35 copies are known to exist in various archival repositories around the world. In this paper we begin with a brief introduction to the Book of the Fixed Stars and provide biographical material about al-Sūfī before reviewing his investigation of stars, star clusters, nebulae and galaxies in his book. We examine al-Sūfī’s novel stellar magnitude system, his comments on star colours, and stars mentioned in his book but not in the Almagest. We conclude with a listing of star clusters, nebulae and galaxies, including the earliest-known mention of the Great Nebula in Andromeda.