'DARK STARS' AND A NEW INTERPRETATION OF THE ANCIENT GREEK STELLAR MAGNITUDE SYSTEM

Abstract

The role of 'dark stars' in astronomy is examined. Ptolemy, in his <italic>Almagest</italic>, included 12 dark stars in his star catalogue, without offering any explanation of their meaning. Manuscripts in Arabic, Hebrew, Persian, Latin and Greek are examined to highlight and resolve conflicting statements about the star catalogue in the <italic>Almagest</italic>. Ptolemy's ivy leaf and the five dark stars associated with it is traced from its origin in an ancient Babylonian tablet to a Byzantine manuscript, thus establishing a transmission of descriptive astronomy spanning three millennia. Partly by resolving a long-standing misinterpretation of a text by Hipparchus on stellar magnitudes, this paper demonstrates clearly for the first time that Ptolemy employed <underline>two</underline> systems to describe stellar brightness: numerical and descriptive. The scale of 6 magnitudes employed by Ptolemy continued a system used by Manilius, not that of Hipparchus as many modern texts claim. Ptolemy's numerical magnitudes are at least partly his own, but 'dark star' is a descriptive magnitude that enters the work of Ptolemy from Eudoxus; the research presented here offers the first explanation of dark stars. The other descriptive magnitude Ptolemy uses, nebulous, comes from the work of Aratus, which in turn derives from Eudoxus. The astronomical heritage embodied in dark stars in European astronomy and literature is surveyed to the present day.