Proxima Centauri (Latin proxima: meaning 'next to' or 'nearest to') is a red dwarf star approximately 4.2 light-years (4.0 × 1013 km) distant in the constellation of Centaurus. It was discovered in 1915 by Robert Innes, the Director of the Union Observatory in South Africa. The star is the nearest star to the Sun. Its distance to the second and third nearest star, which form the binary star Alpha Centauri, is only 0.21 ly (15,000 ± 700 astronomical units [AU]).