A large and prominent southern constellation, representing a centaur. Its brightest star, Alpha Centauri (Rigil Kentaurus), is actually a triple star, one member of which, Proxima Centauri, is the closest star to the Sun. Beta Centauri (Hadar) is another bright star. Omega Centauri is the most prominent globular cluster in the sky, and NGC 5128 is a peculiar radio galaxy known as Centaurus A. NGC 3918 is a planetary nebula known as the Blue Planetary.