The Alpha Centauri star system (also known as Rigel Kentaurus) is a trinary system, part of the UFE. At a distance of only 4.37 light-years from Earth, it is the closest star system to Sol. It consists of three stars: the pair Alpha Centauri A and Alpha Centauri B and a small and faint red dwarf, Proxima Centauri, that is gravitationally bound to the other two. To the unaided eye, the two main components appear as a single object of an apparent visual magnitude of −0.27, forming the brightest star in the southern constellation Centaurus and the third-brightest star in the night sky, outshone only by Sirius and Canopus.