Omicron1 Centauri

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

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

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
Evolutionary stage	Yellow hypergiant
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	10,100+2,700 −1,100 ly (3,110+820 −530 pc)[7]
Absolute magnitude (MV)	−9.0[4]
Details
Mass	27±5.4[8] M☉
Radius	440±35[8] R☉
Luminosity	68,000[9] L☉
Surface gravity (log g)	0.19[10] cgs
Temperature	5,700[9] K
Age	10–12[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
SIMBAD	data

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.^[12] 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.^[13][14] It is the MK spectral standard for class G3 O-Ia,^[15] indicating a highly luminous mass-losing hypergiant star. It has also be classified as F8 Ia0^[16] and F7 Ia/ab.^[17] 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,^[18] although it appears to be a foreground star unrelated to the other two.^[19] ο¹ Cen is located very close to V382 Carinae, the brightest yellow hypergiant star in the night sky.

See also

• astronomy portal

Omicron² Centauri