Mu Cephei (or "miu Cep") is a bright, red semiregular supergiant (type SRc) star, varying between 3rd and 6th magnitude. It was dubbed "The Garnet Star" by William Herschel in 1783, and has been known to be variable since the mid-19th Century. Mu Cephei is a pulsating star whose surface heaves in and out on timescales defined by the size of its surface. Physically it is one of the largest stars in the sky, larger in diameter than most Mira-type variables. Mu Cephei is also a massive star, probably more than 20 times the mass of the sun. Such stars are fated to live bright but very short lives; the more massive the star, the shorter its life. The Sun might live for ten billion years, but mu Cep and other massive stars may only live for a few million. It will almost certainly end its life as a Type II supernova, an end that might come a million years from now, or perhaps much, much sooner. For now, this Garnet gem continues to shine in northern skies, undergoing slow, stately variations of hundreds of days. Mu Cep is a good target for binocular observers as well as photoelectric observers. The AAVSO International Database contains not only data from AAVSO observers, but also from other historic observers going back to the time of Argelander.
Special note to observers: please submit data for this star using the names "* mu Cep" or "miu Cep". Data submitted as "mu Cep" will be interpreted as "MU Cep" by WebObs.
Prepared By: Matthew Templeton