Gamma Centauri
Gamma Centauri, Latinized from γ Centauri, is a binary star system in the southern constellation of Centaurus. It has the proper name Muhlifain, not to be confused with Muliphein, which is γ Canis Majoris; both names derive from the same Arabic root. The system is visible to the naked eye as a single point of light with a combined apparent visual magnitude of +2.17; individually they are third-magnitude stars.
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Centaurus |
| Right ascension | 12h 41m 31.04008s |
| Declination | −48° 57′ 35.5375″ |
| Apparent magnitude (V) | +2.17 (+2.85/+2.95) |
| Characteristics | |
| Spectral type | A1IV+ (A1IV + A0IV) |
| U−B color index | −0.01 |
| B−V color index | −0.01 |
| Astrometry | |
| Radial velocity (Rv) | −5.5 km/s |
| Proper motion (μ) | RA: −185.72 mas/yr Dec.: +5.79 mas/yr |
| Parallax (π) | 25.06 ± 0.28 mas |
| Distance | 130 ± 1 ly (39.9 ± 0.4 pc) |
| Absolute magnitude (MV) | −0.81 |
| Orbit | |
| Companion | γ Centauri B |
| Period (P) | 83.57±0.21 yr |
| Semi-major axis (a) | 0.869±0.011″ |
| Eccentricity (e) | 0.793±0.003 |
| Inclination (i) | 113.7±0.7° |
| Longitude of the node (Ω) | 2.6±0.7° |
| Periastron epoch (T) | 1,931.25 ± 0.07 |
| Argument of periastron (ω) (secondary) | 187.9±1.5° |
| Details | |
| Mass | 2.91 M☉ |
| Surface gravity (log g) | 3.52 cgs |
| Temperature | 9,082 K |
| Metallicity | −0.29 |
| Other designations | |
| Database references | |
| SIMBAD | data |
This system is located at a distance of about 130 light-years (40 parsecs) from the Sun based on parallax. In 2000, the pair had an angular separation of 1.217 arcseconds with a position angle of 351.9°. Their positions have been observed since 1897, which is long enough to estimate an orbital period of 84.5 years and a semimajor axis of 0.93 arcsecond. At the distance of this system, this is equivalent to a physical separation of about 93 AU.
The combined stellar classification of the pair is A1IV+; when they are separated out they have individual classes of A1IV and A0IV, suggesting they are A-type subgiant stars in the process of becoming giants. The star Tau Centauri is relatively close to Gamma Centauri, with an estimated separation of 1.72 light-years (0.53 parsecs). There is a 98% chance that they are co-moving stars.