4 Centauri
4 Centauri is a star in the constellation Centaurus. It is a blue-white B-type subgiant with an apparent magnitude of +4.75 and is approximately 640 light years from Earth.
| Observation data Epoch J2000.0 Equinox J2000.0 | |
|---|---|
| Constellation | Centaurus |
| Right ascension | 13h 53m 12.53953s |
| Declination | −31° 55′ 39.3947″ |
| Apparent magnitude (V) | +4.73(+4.72 / +8.47) |
| Characteristics | |
| Spectral type | B6IV / Am |
| U−B color index | −0.56 |
| B−V color index | −0.14 |
| Astrometry | |
| Radial velocity (Rv) | +5.2 ± 2 km/s |
| Proper motion (μ) | RA: -12.72 mas/yr Dec.: -9.48 mas/yr |
| Parallax (π) | 5.12 ± 0.70 mas |
| Distance | approx. 640 ly (approx. 200 pc) |
| Absolute magnitude (MV) | −1.66 |
| Orbit | |
| Primary | 4 Cen Aa |
| Companion | 4 Cen Ab |
| Period (P) | 6.930137 ± 0.000015 |
| Eccentricity (e) | 0.25 ± 0.10 |
| Periastron epoch (T) | 2418823.406 ± 0.10 |
| Argument of periastron (ω) (secondary) | 152 ± 17° |
| Semi-amplitude (K1) (primary) | 21.0 ± 1.5 km/s |
| Orbit | |
| Primary | 4 Cen Ba |
| Companion | 4 Cen Bb |
| Period (P) | 4.8390 ± 0.0001 |
| Eccentricity (e) | 0.05 ± 0.02 |
| Periastron epoch (T) | 2442916.55 ± 0.09 |
| Argument of periastron (ω) (secondary) | 51 ± 20° |
| Semi-amplitude (K1) (primary) | 16.9 ± 3.5 km/s |
| Other designations | |
| 4 Cen A: SAO 204944, GC 18755, CD–31° 10729 | |
| 4 Cen B: SAO 204943, GC 18754, CD–31° 10727 | |
| Database references | |
| SIMBAD | 4 Cen |
| 4 Cen A | |
| 4 Cen B | |
4 Centauri is a hierarchical quadruple star system. The primary component of the system, 4 Centauri A, is a spectroscopic binary, meaning that its components cannot be resolved but periodic Doppler shifts in its spectrum show that it must be orbiting. 4 Centauri A has an orbital period of 6.927 days and an eccentricity of 0.23. Because light from only one of the stars can be detected (i.e. it is a single-lined spectroscopic binary), some parameters such as its inclination are unknown. The secondary component, is also a single-lined spectroscopic binary. It has an orbital period of 4.839 days and an eccentricity of 0.05. The secondary component is a metallic-lined A-type star. The two pairs themselves are separated by 14 arcseconds; one orbit would take at least 55,000 years.