Pi Centauri
Binary star in the constellation Centaurus
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Pi Centauri is a binary star system in the southern constellation of Centaurus. Its name is a Bayer designation that is Latinized from π Centauri, and abbreviated Pi Cen or π Cen. This pair has a blue-white hue and is visible to the naked eye with a combined apparent visual magnitude of +3.90.[1] The system is located at a distance of approximately 360 light years from the Sun based on parallax,[2] and is drifting further away with a radial velocity of around +9 km/s.[1] It is a member of the Lower Centaurus–Crux subgroup of the Scorpius–Centaurus association.[11]
 | |
| Observation data Epoch J2000.0 Equinox J2000.0 | |
|---|---|
| Constellation | Centaurus[1] |
| Right ascension | 11h 21m 00.41s[2] |
| Declination | −54° 29′ 27.7″[2] |
| Apparent magnitude (V) | +3.90[1] (4.08 + 5.65)[3] |
| Characteristics | |
| Evolutionary stage | main sequence |
| Spectral type | B5Vn[4] + B6V[5] |
| B−V color index | −0.157±0.015[1] |
| Astrometry | |
| Radial velocity (Rv) | +9.4±3.7[1] km/s |
| Proper motion (μ) | RA: −35.85±0.34< mas/yr[2] Dec.: −1.72±0.27 mas/yr[2] |
| Parallax (π) | 9.12±0.34 mas[2] |
| Distance | 360 ± 10 ly (110 ± 4 pc) |
| Absolute magnitude (MV) | −1.30[1] |
| 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 |
| Age | 13.9[9] Myr |
| B | |
| Mass | 3.68[6] M☉ |
| Other designations | |
| π Cen, CPD−53°4498, FK5 428, GC 15601, HD 98718, HIP 55425, HR 4390, SAO 238986, CCDM J11210-5429[10] | |
| 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[1] 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]