variable star
A star that changes in brightness. Variable stars fall into two general categories: intrinsic variables, in which physical changes, such as pulsations or eruptions, are involved, and extrinsic variables, in which the light output fluctuates due to eclipses or stellar rotation. Further classification is complex; originally it was based on a star’s light-curve, amplitude, and periodicity (or lack of it), but is now more closely linked to the physical processes underlying the variability. The standard reference for classification is the General Catalogue of Variable Stars. Specific types of variable star are often named after a prototype (see variable star naming). Additionally, a star may belong to more than one category of variable. Click on entries listed below for further details.
Cataclysmic variable (outbursts on star’s surface or accretion disk, or stellar explosion)
Supernova (sudden, dramatic, final magnitude increase as result of stellar explosion) Nova (fusion explosion increases brightness and then fades)
Recurrent nova (system that has undergone 2 or more recorded nova-like eruptions) U Geminorum star (close binary system with Sun-like star and white dwarf) Z Camelopardalis star (no well-defined quiescence; “standstills” of brightness) SU Ursae Majoris star (orbital period < 2 hours; two distinct outbursts) Magnetic cataclysmic variable (close binary system with highly magnetic white dwarf) AM Herculis star (strong circular polarization; dwarf in synchronized rotation) DQ Herculis star (similar to AM Her but no synchronized rotation) Symbiotic star (semiperiodic nova-like outbursts of up to 3 mag.) Z Andromedae star
X-ray variables (X-ray emissions from binary star, including compact component)
Eclipsing variable (binary system with an orbital plane lying near the observer’s line-of-sight)
Algol star (spherical components; eclipses identifiable from light curve) Beta Lyrae star (tidally-distorted components; continuous changes in brightness) W Ursae Majoris star (components almost touching)
Rotating variable (changing light output due to dark/light spots on star’s surface)
