Variable star

Variable stars are broadly classified into two major categories, stars in which the variablility in brightness are attributable to physical processes within the star itself (eg. pulsating stars) and those in which the variations observed are caused by external factors more closely related to our perspective when viewing the stars (eg. eclipse variables).

Naming conventions

Some prominent variable stars that are bright enough to be visible to the naked eye have common names like Mira or Algol while others have bayer designations like β Cephei but the majority of variable stars are named according to the system devised by the 19th century astronomer Friedrich Argelander. According to this system the first variable star discovered in any given constellation is designated R followed by the genitive of the constellation name (eg. R Andromedae). Subsequent discoveries in the same constellation receive the designations S through Z followed by RR through RZ, SS through SZ and so forth up to and including ZZ. After these have been exhausted the next variable receives the designation AA after which the system continues through to QZ while omitting the letter J from the sequence. this system leaves room for 334 variable stars to be so designated whereafter variables will simple receive the designation V335, V336 etcetera. like in the case of the star V335 Sagitarii.

History

Not counting the occasional supernova, the first variable star to be identified was Mira or ο Ceti which was found to be periodically invisible by German astronomer and theologian David Fabricius in the late 16th and early 17th centuries. By the turn of the 19th century about a dozen variable stars were known but with the advent of modern asto-photography the number of discoveries ballooned with tens of thousands known to exist in a variety of different classes.