Alpha Centauri

Alpha Centauri (α Centauri, abbreviated Alpha Cen, α Cen) is a star system in the Orion Arm of the Milky Way galaxy, and is the closest star system to the Solar System, being 4.37 light-years (1.34 pc) from the Sun.[5] It consists of three stars: the pair Alpha Centauri A (also named Rigil Kentaurus[12]) and Alpha Centauri B together with a small and faint red dwarf, Alpha Centauri C (also named Proxima Centauri[12]), that may be gravitationally bound to the other two.[13] 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 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.[14]During the pair's 79.91-year orbit about a common centre,[15] the distance between them varies from about that between Pluto and the Sun to that between Saturn and the Sun.

Proxima Centauri (α Cen C) is at the slightly smaller distance of 4.24 light-years (1.30 pc) from the Sun, making it the closest star to the Sun, even though it is not visible to the naked eye. The separation of Proxima from Alpha Centauri AB is about 15,000 astronomical units (0.24 ly; 0.07 pc),[16] equivalent to 500 times the size of Neptune's orbit. Proxima Centauri b, an Earth-sized exoplanet in the habitable zone of Proxima Centauri, has been detected[17] and may be a destination of future interstellar spacecraft, including a fleet of StarChip spacecraft currently being developed for a flyby mission by the Breakthrough Starshot project.