Omicron<sup>1</sup> Centauri is a yellow hypergiant star in the southern constellation of Centaurus. Its name is a Bayer designation that is Latinized from ÿ<sup>1</sup> Centauri, and abbreviated Omicron<sup>1</sup> Cen or ÿ<sup>1</sup> Cen. It is approximately 9,400 light-years from Earth.
ÿ<sup>1</sup> Centauri is a yellow G-type supergiant or hypergiant with a mean apparent magnitude of +5.13. Daniel Joseph Kelly O'Connell discovered that the star is a variable star by studying photographic plates taken from 1934 to 1952, and announced his discovery in 1961. It is classified as a semiregular variable star and its brightness varies from magnitude +5.8 to +6.6 with a period of 200 days. Other studies have reported only small brightness variations. It has been assigned the spectral types F8 Ia0 and F7 Ia/ab, indicating an F-type hypergiant or F-type supergiant respectively, but this has been revised to G3_0 Ia in 1989, indicating that it is a G-type hypergiant, and has been listed as the spectral standard for this class. The star is around 400 times larger than the Sun and roughly 210,000 times more luminous.
ÿ<sup>1</sup> Cen forms a very close naked eye double star with ÿ<sup>2</sup> Centauri, a hotter blue supergiant that may be physically associated. ÿ<sup>1</sup> Cen also has an 11th magnitude companion only 13.5" distant, although it appears to be a foreground star unrelated to the other two.