Omicron1 Centauri
Omicron1 Centauri is a star in the southern constellation of Centaurus. Its name is a Bayer designation that is Latinized from ο1 Centauri, and abbreviated Omicron1 Cen or ο1 Cen. It is approximately 10,000 light years from Earth, though this is very uncertain.
ο1 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 is the MK spectral standard for class G3 O-Ia, indicating a highly luminous mass-losing hypergiant star. It has also be classified as F8 Ia0 and F7 Ia/ab. The size, luminosity, and distance are equally uncertain.
ο1 Cen forms a very close naked eye double star with ο2 Centauri, a hotter blue supergiant that may be physically associated. ο1 Cen also has an 11th magnitude companion only 13.5" distant, although it appears to be a foreground star unrelated to the other two. ο1 Cen is located very close to V382 Carinae, the brightest yellow hypergiant star in the night sky.