Omicron1 Centauri
| Observation data Epoch J2000.0 Equinox J2000.0 | |
|---|---|
| Constellation | Centaurus |
| Right ascension | 11h 31m 46.07s |
| Declination | −59° 26′ 31.4″ |
| Apparent magnitude (V) | +5.13 |
| Characteristics | |
| Evolutionary stage | Yellow hypergiant |
| Spectral type | G3_0-Ia |
| B−V color index | +1.08 |
| Variable type | SRd |
| Astrometry | |
| Radial velocity (Rv) | −20.00 km/s |
| Proper motion (μ) | RA: −4.491 mas/yr Dec.: +1.604 mas/yr |
| Parallax (π) | 0.3254±0.0734 mas |
| Distance | 9,390 ± 330 ly (2,880±100 pc) |
| Absolute magnitude (MV) | −9.0 |
| Details | |
| Mass | 27±5.4 M☉ |
| Radius | 403±41 R☉ |
| Luminosity | 210,000+88,000 −82,000 L☉ |
| Surface gravity (log g) | 0.19 cgs |
| Temperature | 5,700 K |
| Age | 10–12 Myr |
| Other designations | |
| ο1 Cen, AAVSO 1127-58, CD−58°4100, GC 15818, HD 100261, HIP 56243, HR 4441, SAO 239145, CCDM J11318-5927 | |
| Database references | |
| SIMBAD | data |
Omicron1 Centauri is a yellow hypergiant 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 9,400 light-years from Earth.
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 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.
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.