The Cepheid Variables, so named because the naked-eye star delta Cephei is a typical example and first discovered, are all giants or super-giant stars. The pole star Alpha Ursa Minor is a Cepheid variable. The Cepheids are pulsating stars with periods ranging from a few days to several months and spectral types from F or G (at maximum light). All are reddest at minimum light, but never of spectrum later than K. The Cepheid variables are most important because they are bright enough to be observed in other galaxies besides our own, such as Andromeda. Since we know that the Ionger the period of a Cepheid, the more luminous it is, these variables have served as the 'standard candles' with which to explore external galaxies such as the Magellanic Clouds. Over 600 Cepheids have been discovered in other galaxies, as well as our own and this group of pulsating stars are often called Classical Cepheids. Cepheids are associated with dust filled regions of space.

Copyright (c) 1997-99 Michael Erlewine