Proxima Centauri was found to share the same proper motion as Alpha Centauri in 1915 by Robert Innes while he was Director of the Union Observatory in Johannesburg , South Africa . In 1915 , Robert Innes , Director of the Union Observatory in Johannesburg , South Africa , discovered a star that had the same proper motion as Alpha Centauri . He suggested it be named Proxima Centauri .