Alpha Centauri is a star.
Alpha Centauri ( α Centauri , abbreviated Alpha Cen , α Cen ) is the closest star system to the Solar System , being 4.37 ly from the Sun . It consists of three stars : the double star Alpha Centauri A ( also named Rigil Kentaurus ) and Alpha Centauri B together with a small and faint red dwarf , Alpha Centauri C ( also named Proxima Centauri ) , that may be gravitationally bound to the other two . To the unaided eye , the two main components appear as a single point of light with an apparent visual magnitude of − 0.27 , forming the brightest star in the southern constellation of Centaurus and is the third-brightest star in the night sky , outshone only by Sirius and Canopus . Alpha Centauri A ( α Cen A ) has 1.1 times the mass and 1.519 times the luminosity of the Sun , while Alpha Centauri B ( α Cen B ) is smaller and cooler , at 0.907 times the Sun 's mass and 0.445 times its visual luminosity . Proxima Centauri ( α Cen C ) is at the slightly smaller distance of 1.30 pc from the Sun , making it the closest star to the Sun , even though it is not visible to the naked eye .