Pi Centauri

Pi Centauri, Latinized from π Centauri, is a binary star system in the southern constellation of Centaurus. It has a blue-white hue and is visible to the naked eye with a combined apparent visual magnitude of +3.90.^[2] The system is located at a distance of approximately 360 light years from the Sun based on parallax,^[1] and is drifting further away with a radial velocity of around +9 km/s.^[2] It is a member of the Lower Centaurus–Crux subgroup of the Scorpius–Centaurus association.^[10]

Pi Centauri

Observation data Epoch J2000.0      Equinox J2000.0
Constellation	Centaurus
Right ascension	11h 21m 00.41s[1]
Declination	−54° 29′ 27.7″[1]
Apparent magnitude (V)	+3.90[2] (4.08 + 5.65)[3]
Characteristics
Spectral type	B5Vn[4] + B6V[5]
B−V color index	−0.157±0.015[2]
Astrometry
Radial velocity (Rv)	+9.4±3.7[2] km/s
Proper motion (μ)	RA: −35.85±0.34[1] mas/yr Dec.: −1.72±0.27[1] mas/yr
Parallax (π)	9.12±0.34 mas[1]
Distance	360 ± 10 ly (110 ± 4 pc)
Absolute magnitude (MV)	−1.30[2]
Orbit[6]
Period (P)	39.0±0.19 yr
Semi-major axis (a)	0.2263±0.0011″
Eccentricity (e)	0.8530±0.0040
Inclination (i)	19.4±4.9°
Longitude of the node (Ω)	327.8±3.9°
Periastron epoch (T)	2010.410±0.037
Argument of periastron (ω) (secondary)	340.3±4.0°
Details
A
Mass	6.43[6] M☉
Temperature	16,760[7] K
Rotational velocity (v sin i)	340[8] km/s
B
Mass	3.68[6] M☉
Other designations
π Cen, BD−53°4498, FK5 428, GC 15601, HD 98718, HIP 55425, HR 4390, SAO 238986, CCDM J11210-5429[9]
Database references
SIMBAD	data

The magnitude +4.08^[3] primary, designated component A, is a B-type main-sequence star with a stellar classification of B5Vn,^[4] where the 'n' suffix indicates broad, diffuse (nebulous) lines due to rapid rotation. This star is spinning with a projected rotational velocity of 340 km/s, giving it an equatorial bulge that is 22% larger than the polar radius.^[8] It has 6.4^[6] times the mass of the Sun and is radiating 783^[2] times the Sun's luminosity from its photosphere at an effective temperature of 16,760 K.^[7]

The secondary companion, component B, is magnitude +5.65^[3] with a class of B6V^[5] and 3.7^[6] times the Sun's mass. The pair orbit around their common barycentre once every 39 years with an eccentricity of 0.8530. The semi-major axis of the companion is 0.23 arcseconds at an inclination of 19.4°.^[6]