Omicron1 Centauri

For other star systems with this Bayer designation, see Omicron Centauri.
ο1 Centauri
Location of ο1 Cen (circled)
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]
Distance10,150+2,660
−1,710 ly
(3,110+820
−530 pc)[7]
Absolute magnitude (MV)−9.0[4]
Details
Mass27±5.4[8] M☉
Radius440±35[8] R☉
Luminosity68,000[9] L☉
Surface gravity (log g)0.19[10] cgs
Temperature5,700[9] K
Age10–12[9] Myr
Other designations
HR 4441, HD 100261, CD−58°4100, HIP 56243, SAO 239145, GC 15818, CCDM J11318-5927, AAVSO 1127-58
Database references
SIMBADdata

Omicron1 Centauri (ο1 Cen, ο1 Centauri) is a star in the constellation Centaurus. It is approximately 10,000 light years from Earth.

A light curve for Omicron1 Centauri, adapted from O'Connell (1961)[11]

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.[12][13] It is the MK spectral standard for class G3 O-Ia,[14] indicating a highly luminous mass-losing hypergiant star. It has also be classified as F8 Ia0[15] and F7 Ia/ab.[16] 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,[17] Although it appears to be a foreground star unrelated to the other two.[18]

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