4 Centauri

This article is about h Centauri and is not to be confused with H 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.

4 Centauri

Observation data Epoch J2000.0      Equinox J2000.0
Constellation	Centaurus[1]
Right ascension	13h 53m 12.53953s[2]
Declination	−31° 55′ 39.3947″[2]
Apparent magnitude (V)	+4.73[3](+4.72[4] / +8.47[5])
Characteristics
Spectral type	B6IV[6] / Am[6]
U−B color index	−0.56[3]
B−V color index	−0.14[3]
Astrometry
Radial velocity (Rv)	+5.2±2[7] km/s
Proper motion (μ)	RA: -12.72[2] mas/yr Dec.: -9.48[2] mas/yr
Parallax (π)	5.12±0.70 mas[2]
Distance	approx. 640 ly (approx. 200 pc)
Absolute magnitude (MV)	−1.66[1]
Orbit[6]
Primary	4 Cen Aa
Companion	4 Cen Ab
Period (P)	6.930137±0.000015 d
Eccentricity (e)	0.25±0.10
Argument of periastron (ω) (secondary)	152±17°
Semi-amplitude (K1) (primary)	21.0±1.5 km/s
Orbit[6]
Primary	4 Cen Ba
Companion	4 Cen Bb
Period (P)	4.8390±0.0001 d
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
h Cen, HD 120955, HR 5221, HIP 67786, CCDM J13532-3156[8]
4 Cen A: SAO 204944, GC 18755, CD−31°10729[9]
4 Cen B: SAO 204943, GC 18754, CD−31°10727[10]
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.^[11] 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.^[6]