Variable When an Astrophysicist talks about variable stars, s/he usually means a dramatically variable star Some are variable even to the naked eye, once you know what you are looking for –Mira ( Ceti): T ~ 1 year AKA “Wonderful” in Latin –Algol ( Persei): T ~ 1 week AKA “The Demon” in Arabic –Suggests ancient peoples noticed these changes Intrinsic variability due to instability in the Hydrostatic Equilibrium Extrinsic variability due to shape, bright spots, rotation, neighbors
