The Alpha Centauri system is located 4.37 Earth light years from Sol, making it the closest star system to the Sol System. Although it appears to the unaided human eye from earth as a single object, Alpha Centauri is actually a binary star system whose combined visual magnitude makes it the third brightest star seen from Earth.
Its individual component stars are named Alpha Centauri A, with 110% of the mass and 151.9% the luminosity of Sol, and Alpha Centauri B, at 90.7% of Sol's mass and 44.5% of its luminosity. During the pair's 79.91-year orbit about a common center, the distance between them varies from about that between the Kuiper belt and Sol to that between Saturn and Sol.
A third star, known as Proxima Centauri, Proxima, or Alpha Centauri C, is probably gravitationally associated with Alpha Centauri AB. Proxima is at the slightly smaller distance of 4.24 Earth light years from Sol, making it the closest star to Sol, even though it is not visible to the naked human eye. The separation of Proxima from Alpha Centauri AB is about 0.2 Earth light years.