2 Centauri

This article is about g Centauri and is not to be confused with G Centauri.

2 Centauri is a single^[13] star in the southern constellation of Centaurus, located approximately 183 light-years from Earth.^[3] It has the Bayer designation g Centauri;^[12] 2 Centauri is the Flamsteed designation. This object is visible to the naked eye as faint, red-hued star with an apparent visual magnitude of 4.19.^[4] It is moving away from the Earth with a heliocentric radial velocity of +41 km/s.^[8] The star is a member of the HR 1614 supercluster.^[14]

2 Centauri

A light curve for V806 Centauri. The main plot shows the long term variability from Hipparcos data,[1] and the inset plot shows the variability over the 26.5 day period, using data from Tabur et al. (2009).[2] The green curve shows the best-fit sine wave, which has an amplitude of 18 millimagnitudes.
Observation data Epoch J2000.0      Equinox J2000.0
Constellation	Centaurus
Right ascension	13h 49m 26.72175s[3]
Declination	−34° 27′ 02.7929″[3]
Apparent magnitude (V)	4.19[4] (4.16–4.26)[5]
Characteristics
Spectral type	M5 III[6]
U−B color index	+1.44[7]
B−V color index	+1.49[7]
Variable type	SRb[5]
Astrometry
Radial velocity (Rv)	+40.7±0.7[8] km/s
Proper motion (μ)	RA: −41.68±0.23[3] mas/yr Dec.: −59.77±0.18[3] mas/yr
Parallax (π)	17.82±0.21 mas[3]
Distance	183 ± 2 ly (56.1 ± 0.7 pc)
Absolute magnitude (MV)	+0.51[9]
Details
Radius	82.4[10] R☉
Luminosity	71.96[4] L☉
Temperature	3,398[11] K
Other designations
g Centauri, 2 Cen, V806 Cen, CD−33°9358, GC 18666, HD 120323, HIP 67457, HR 5192, SAO 204875[12]
Database references
SIMBAD	data

This is an evolved red giant star with a stellar classification of M5 III.^[6] In 1951, Alan William James Cousins announced that the star, then called g Centauri, is a variable star.^[15] It was given its variable star designation, V806 Centauri, in 1978.^[16] It is classified as a semiregular variable star and its brightness varies from magnitude +4.16 to +4.26^[5] with a period of 12.57 days.^[17] The star has around 70^[18] times the Sun's radius and is radiating 72^[4] times the Sun's luminosity from its enlarged photosphere at an effective temperature of 3,398 K.^[11]