Omicron1 Centauri (ο1 Cen, ο1 Centauri) is a star in the constellation Centaurus. It is approximately 10,000 light years from Earth.
  | |
| Observation data Epoch J2000.0 Equinox J2000.0 | |
|---|---|
| Constellation | Centaurus |
| Right ascension | 11h 31m 46.07s[1] |
| Declination | −59° 26′ 31.4″[1] |
| Apparent magnitude (V) | +5.13[2] |
| Characteristics | |
| Spectral type | G3 0-Ia[3][4] |
| B−V color index | +1.08[2] |
| Variable type | SRd[5] |
| Astrometry | |
| Radial velocity (Rv) | −20.00[6] km/s |
| Proper motion (μ) | RA: −4.491[1] mas/yr Dec.: +1.604[1] mas/yr |
| Parallax (π) | 0.3254 ± 0.0734 mas[1] |
| Distance | approx. 10,000 ly (approx. 3,100 pc) |
| Absolute magnitude (MV) | −9.0[4] |
| Details | |
| Mass | 17[7] M☉ |
| Radius | 270[7] R☉ |
| Luminosity | 68,000[7] L☉ |
| Surface gravity (log g) | 0.19[8] cgs |
| Temperature | 4,873[9] K |
| Age | 10–12[7] Myr |
| Other designations | |
| Database references | |
| SIMBAD | data |
ο1 Centauri is a yellow G-type supergiant or hypergiant with a mean apparent magnitude of +5.13. 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.[5] Other studies have reported only small brightness variations.[11][12] It is the MK spectral standard for class G3 O-Ia,[13] indicating a highly luminous mass-losing hypergiant star. It has also be classified as F8 Ia0[14] and F7 Ia/ab.[15] The size, luminosity, and distance are equally uncertain.
ο1 Cen forms a very close naked eye double star with ο2 Centauri, a hotter supergiant that may be physically associated. ο1 Cen also has an 11th magnitude companion only 13.5" distant,[16] Although it appears to be a foreground star unrelated to the other two.[17]