Betelgeuse - Observational History

Observational History

Betelgeuse and its red coloration have been noted since antiquity; the classical astronomer Ptolemy described its color as ὑπόκιρρος (hypókirros), a term which was later described by a translator of Ulugh Beg's Zij-i Sultani as rubedo, Latin for "ruddiness". In the nineteenth century, before modern systems of stellar classification, Angelo Secchi included Betelgeuse as one of the prototypes for his Class III (orange to red) stars. By contrast, three centuries before Ptolemy, Chinese astronomers observed Betelgeuse as having a yellow coloration, suggesting that the star may have spent time as a yellow supergiant around the beginning of the common era, an intriguing possibility given current research into the complex circumstellar environment of these stars.