Beta Centauri
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).
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Centaurus |
| Right ascension | 14h 03m 49.40535s |
| Declination | −60° 22′ 22.9266″ |
| Apparent magnitude (V) | 0.61 |
| Characteristics | |
| U−B color index | –0.98 |
| B−V color index | –0.23 |
| β Cen Aa | |
| Spectral type | B1 III |
| Variable type | β Cep/SPB |
| β Cen Ab | |
| Spectral type | B1 III |
| β Cen B | |
| Spectral type | B1V? |
| Astrometry | |
| Radial velocity (Rv) | +9.59+0.23 −0.21 km/s |
| Proper motion (μ) | RA: –33.27 mas/yr Dec.: –23.16 mas/yr |
| Parallax (π) | 8.32 ± 0.50 mas |
| Distance | 390 ± 20 ly (120 ± 7 pc) |
| Absolute magnitude (MV) | −4.9±0.2 |
| Orbit | |
| Primary | β Cen Aa |
| Companion | β 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 | |
| Primary | β Cen A |
| Companion | β Cen B |
| Period (P) | 288.267 yr |
| Semi-major axis (a) | 0.870″ |
| Details | |
| Luminosity | 66,100 L☉ |
| Age | 14.1±0.6 Myr |
| β Cen Aa | |
| Mass | 12.02±0.13 M☉ |
| Radius | 9 R☉ |
| Luminosity | 31,600+18,500 −11,700 L☉ |
| Surface gravity (log g) | 3.55±0.11 cgs |
| Temperature | 25,000±2,000 K |
| Rotational velocity (v sin i) | 190±20 km/s |
| β Cen Ab | |
| Mass | 10.58±0.18 M☉ |
| Radius | 9 R☉ |
| Luminosity | 25,100+14,700 −9,300 L☉ |
| Surface gravity (log g) | 3.55±0.11 cgs |
| Temperature | 23,000±2,000 K |
| Rotational velocity (v sin i) | 75±15 km/s |
| β Cen B | |
| Mass | 4.61 M☉ |
| Other designations | |
| Database references | |
| SIMBAD | data |
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