Alpha Centauri is actually a binary star system consisting of Alpha Centauri A and B located in the southern constellation Centaurus. It is the closest star system to our own Solar System. A third star, Proxima Centauri, is located slightly farther at 4.2 light years and is considered part of the Alpha Centauri system. Proxima Centauri is the closest star to our Sun. Alpha Centauri A is the larger of the two main stars and most similar to the Sun, while Alpha Centauri B is smaller and less luminous than our Sun.