Beta Centauri

This article is about β Centauri. For B Centauri, see HD 102964. For b Centauri, see HD 129116. For other uses of the name "Hadar", see Hadar (disambiguation). Not to be confused with Alpha Centauri B or b Centauri b.
β Centauri/Hadar
Location of β Centauri (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Centaurus
Right ascension 14h 03m 49.40535s[1]
Declination −60° 22′ 22.9266″[1]
Apparent magnitude (V) 0.61[2]
Characteristics
U−B color index –0.98[2]
B−V color index –0.23[2]
β Cen Aa
Spectral type B1 III[3]
Variable type β Cep/SPB[4]
β Cen Ab
Spectral type B1 III[3]
β Cen B
Spectral type B1V?[3]
Astrometry
Radial velocity (Rv)+9.59+0.23
−0.21[4] km/s
Proper motion (μ) RA: –33.27[1] mas/yr
Dec.: –23.16[1] mas/yr
Parallax (π)8.32 ± 0.50 mas[1]
Distance390 ± 20 ly
(120 ± 7 pc)
Absolute magnitude (MV)−4.9±0.2[5]
Orbit[4]
Primaryβ Cen Aa
Companionβ Cen Ab
Period (P)356.915±0.015 d
(0.97720±0.00004 yr)
Semi-major axis (a)0.02515+0.09
−0.08″
Eccentricity (e)0.8245±0.006
Inclination (i)67.68±0.12°
Longitude of the node (Ω)108.80+0.14
−0.15°
Periastron epoch (T)2452000.15202
Argument of periastron (ω)
(secondary)		60.87+0.26
−0.25°
Semi-amplitude (K1)
(primary)		62.9 km/s
Semi-amplitude (K2)
(secondary)		72.35 km/s
Orbit[6]
Primaryβ Cen A
Companionβ Cen B
Period (P)288.267 yr
Semi-major axis (a)0.870″
Details
Luminosity66,100[5] L☉
Age14.1±0.6[3] Myr
β Cen Aa
Mass12.02±0.13[4] M☉
Radius9.48 ± 2.66[5][a] R☉
Luminosity31,600+18,500
−11,700[5] L☉
Surface gravity (log g)3.55±0.11[5] cgs
Temperature25,000±2,000[5] K
Rotational velocity (v sin i)190±20[7] km/s
β Cen Ab
Mass10.58±0.18[4] M☉
Radius9.98 ± 2.88[5][b] R☉
Luminosity25,100+14,700
−9,300[5] L☉
Surface gravity (log g)3.55±0.11[5] cgs
Temperature23,000±2,000[5] K
Rotational velocity (v sin i)75±15[7] km/s
β Cen B
Mass4.61[6] M☉
Other designations
Agena, Hadar[8], CD−59°5365, FK5 518, GC 18971, HD 122451, HIP 68702, HR 5267, SAO 252582, CCDM J14038-6022, LHS 51[9]
Database references
SIMBADdata

Beta Centauri is a triple star system in the southern constellation of Centaurus. It is officially called Hadar (/ˈheɪdɑːr/). The Bayer designation of Beta Centauri is Latinised from β Centauri, and abbreviated Beta Cen or β Cen. The system's combined apparent visual magnitude of 0.61 makes it the second-brightest object in Centaurus and the eleventh brightest star in the night sky. According to parallax measurements from the astrometric Hipparcos satellite, the distance to this system is about 390 light-years (120 parsecs).

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