# Pi Centauri

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Binary star in the constellation Centaurus

Pi Centauri Location of π Centauri (circled in red) 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

**Pi Centauri** is a [binary star](/source/Binary_star) system in the southern [constellation](/source/Constellation) of [Centaurus](/source/Centaurus). Its name is a [Bayer designation](/source/Bayer_designation) that is [Latinized](/source/Romanization_of_Greek) from π Centauri, and abbreviated Pi Cen or π Cen. This pair has a blue-white hue and is visible to the [naked eye](/source/Naked_eye) with a combined [apparent visual magnitude](/source/Apparent_visual_magnitude) of +3.90.[1] The system is located at a distance of approximately 360 [light years](/source/Light_year) from the Sun based on [parallax](/source/Stellar_parallax),[2] and is drifting further away with a [radial velocity](/source/Radial_velocity) of around +9 km/s.[1] It is a member of the Lower Centaurus–Crux subgroup of the [Scorpius–Centaurus association](/source/Scorpius%E2%80%93Centaurus_association).[11]

The magnitude +4.08[3] primary, designated component A, is a [B-type main-sequence star](/source/B-type_main-sequence_star) with a [stellar classification](/source/Stellar_classification) of B5Vn,[4] where the 'n' suffix indicates broad, diffuse (nebulous) [lines](/source/Absorption_line) due to rapid rotation. This star is spinning with a [projected rotational velocity](/source/Projected_rotational_velocity) of 340 km/s, giving it an [equatorial bulge](/source/Equatorial_bulge) that is 22% larger than the polar radius.[8] It has 6.4[6] times the [mass of the Sun](/source/Mass_of_the_Sun) and is radiating 783[1] times the [Sun's luminosity](/source/Sun's_luminosity) from its [photosphere](/source/Photosphere) at an [effective temperature](/source/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](/source/Barycentre) once every 39 years with an [eccentricity](/source/Orbital_eccentricity) of 0.8530. The [semi-major axis](/source/Semi-major_axis) of the companion is 0.23 [arcseconds](/source/Arcsecond) at an inclination of 19.4°.[6]

## References

1. ^ [***a***](#cite_ref-Anderson2012_1-0) [***b***](#cite_ref-Anderson2012_1-1) [***c***](#cite_ref-Anderson2012_1-2) [***d***](#cite_ref-Anderson2012_1-3) [***e***](#cite_ref-Anderson2012_1-4) [***f***](#cite_ref-Anderson2012_1-5) [***g***](#cite_ref-Anderson2012_1-6) [***h***](#cite_ref-Anderson2012_1-7) Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", *[Astronomy Letters](/source/Astronomy_Letters)*, **38** (5): 331, [arXiv](/source/ArXiv_(identifier)):[1108.4971](https://arxiv.org/abs/1108.4971), [Bibcode](/source/Bibcode_(identifier)):[2012AstL...38..331A](https://ui.adsabs.harvard.edu/abs/2012AstL...38..331A), [doi](/source/Doi_(identifier)):[10.1134/S1063773712050015](https://doi.org/10.1134%2FS1063773712050015). [XHIP record for this object](https://vizier.cds.unistra.fr/viz-bin/VizieR-4?-ref=VIZ681510a8389ecb&-out.src=V%2F137D%2FXHIP&-nav=cat%3AV%2F137D%26tab%3A{V%2F137D%2FXHIP}%26key%3Asource%3DV%2F137D%2FXHIP%26HTTPPRM%3A&-source=V%2F137D%2FXHIP&-out=HIP&HIP=55425&-out=Comp&-out=Gr&-out=RAJ2000&-out=DEJ2000&-out=Dist&-out=X&-out=Y&-out=Z&-out=SpType&-out=Simbad&-out=Hpmag&-out=Lum&-out=Cst) at [VizieR](/source/VizieR).

1. ^ [***a***](#cite_ref-van_Leeuwen2007_2-0) [***b***](#cite_ref-van_Leeuwen2007_2-1) [***c***](#cite_ref-van_Leeuwen2007_2-2) [***d***](#cite_ref-van_Leeuwen2007_2-3) [***e***](#cite_ref-van_Leeuwen2007_2-4) van Leeuwen, F. (2007), "Validation of the new Hipparcos reduction", *Astronomy and Astrophysics*, **474** (2): 653–664, [arXiv](/source/ArXiv_(identifier)):[0708.1752](https://arxiv.org/abs/0708.1752), [Bibcode](/source/Bibcode_(identifier)):[2007A&A...474..653V](https://ui.adsabs.harvard.edu/abs/2007A&A...474..653V), [doi](/source/Doi_(identifier)):[10.1051/0004-6361:20078357](https://doi.org/10.1051%2F0004-6361%3A20078357), [S2CID](/source/S2CID_(identifier)) [18759600](https://api.semanticscholar.org/CorpusID:18759600).[Vizier catalog entry](http://webviz.u-strasbg.fr/viz-bin/VizieR-5?-out.add=.&-source=I/311/hip2&recno=55246)

1. ^ [***a***](#cite_ref-Mason2001_3-0) [***b***](#cite_ref-Mason2001_3-1) [***c***](#cite_ref-Mason2001_3-2) Mason, Brian D.; et al. (2001), "The 2001 US Naval Observatory Double Star CD-ROM. I. The Washington Double Star Catalog", *The Astronomical Journal*, **122** (6): 3466, [Bibcode](/source/Bibcode_(identifier)):[2001AJ....122.3466M](https://ui.adsabs.harvard.edu/abs/2001AJ....122.3466M), [doi](/source/Doi_(identifier)):[10.1086/323920](https://doi.org/10.1086%2F323920).

1. ^ [***a***](#cite_ref-Hiltner1969_4-0) [***b***](#cite_ref-Hiltner1969_4-1) Hiltner, W. A.; et al. (July 1969), "MK Spectral Types for Bright Southern OB Stars", *Astrophysical Journal*, **157**: 313–326, [Bibcode](/source/Bibcode_(identifier)):[1969ApJ...157..313H](https://ui.adsabs.harvard.edu/abs/1969ApJ...157..313H), [doi](/source/Doi_(identifier)):[10.1086/150069](https://doi.org/10.1086%2F150069).

1. ^ [***a***](#cite_ref-Edwards1976_5-0) [***b***](#cite_ref-Edwards1976_5-1) Edwards, T. W. (1976), "MK classification for visual binary components", *The Astronomical Journal*, **81**: 245–249, [Bibcode](/source/Bibcode_(identifier)):[1976AJ.....81..245E](https://ui.adsabs.harvard.edu/abs/1976AJ.....81..245E), [doi](/source/Doi_(identifier)):[10.1086/111879](https://doi.org/10.1086%2F111879).

1. ^ [***a***](#cite_ref-Tokovinin2012_6-0) [***b***](#cite_ref-Tokovinin2012_6-1) [***c***](#cite_ref-Tokovinin2012_6-2) [***d***](#cite_ref-Tokovinin2012_6-3) [***e***](#cite_ref-Tokovinin2012_6-4) [***f***](#cite_ref-Tokovinin2012_6-5) Tokovinin, Andrei (2012), "Speckle Interferometry and Orbits of "Fast" Visual Binaries", *The Astronomical Journal*, **144** (2), 56, [arXiv](/source/ArXiv_(identifier)):[1206.1882](https://arxiv.org/abs/1206.1882), [Bibcode](/source/Bibcode_(identifier)):[2012AJ....144...56T](https://ui.adsabs.harvard.edu/abs/2012AJ....144...56T), [doi](/source/Doi_(identifier)):[10.1088/0004-6256/144/2/56](https://doi.org/10.1088%2F0004-6256%2F144%2F2%2F56), [S2CID](/source/S2CID_(identifier)) [118586009](https://api.semanticscholar.org/CorpusID:118586009).

1. ^ [***a***](#cite_ref-Zorec2009_7-0) [***b***](#cite_ref-Zorec2009_7-1) Zorec, J.; et al. (July 2009), "Fundamental parameters of B supergiants from the BCD system. I. Calibration of the (λ_1, D) parameters into Teff", *Astronomy and Astrophysics*, **501** (1): 297–320, [arXiv](/source/ArXiv_(identifier)):[0903.5134](https://arxiv.org/abs/0903.5134), [Bibcode](/source/Bibcode_(identifier)):[2009A&A...501..297Z](https://ui.adsabs.harvard.edu/abs/2009A&A...501..297Z), [doi](/source/Doi_(identifier)):[10.1051/0004-6361/200811147](https://doi.org/10.1051%2F0004-6361%2F200811147), [S2CID](/source/S2CID_(identifier)) [14969137](https://api.semanticscholar.org/CorpusID:14969137).

1. ^ [***a***](#cite_ref-vanBelle2012_8-0) [***b***](#cite_ref-vanBelle2012_8-1) van Belle, Gerard T. (March 2012), "Interferometric observations of rapidly rotating stars", *The Astronomy and Astrophysics Review*, **20** (1) 51, [arXiv](/source/ArXiv_(identifier)):[1204.2572](https://arxiv.org/abs/1204.2572), [Bibcode](/source/Bibcode_(identifier)):[2012A&ARv..20...51V](https://ui.adsabs.harvard.edu/abs/2012A&ARv..20...51V), [doi](/source/Doi_(identifier)):[10.1007/s00159-012-0051-2](https://doi.org/10.1007%2Fs00159-012-0051-2), [S2CID](/source/S2CID_(identifier)) [119273474](https://api.semanticscholar.org/CorpusID:119273474).

1. **[^](#cite_ref-Gratton_et_al_2023_9-0)** Gratton, R.; et al. (October 2023), "Multiples among B stars in the Scorpius-Centaurus association", *Astronomy & Astrophysics*, **678**, id. A93, [arXiv](/source/ArXiv_(identifier)):[2308.09962](https://arxiv.org/abs/2308.09962), [Bibcode](/source/Bibcode_(identifier)):[2023A&A...678A..93G](https://ui.adsabs.harvard.edu/abs/2023A&A...678A..93G), [doi](/source/Doi_(identifier)):[10.1051/0004-6361/202346806](https://doi.org/10.1051%2F0004-6361%2F202346806).

1. **[^](#cite_ref-SIMBAD_10-0)** ["pi Cen"](http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=pi+Cen). *[SIMBAD](/source/SIMBAD)*. [Centre de données astronomiques de Strasbourg](/source/Centre_de_donn%C3%A9es_astronomiques_de_Strasbourg). Retrieved 2019-10-10.

1. **[^](#cite_ref-Bobylev2007_11-0)** Bobylev, V. V.; Bajkova, A. T. (September 2007), "Kinematics of the Scorpius–Centaurus OB association", *Astronomy Letters*, **33** (9): 571–583, [arXiv](/source/ArXiv_(identifier)):[0708.0943](https://arxiv.org/abs/0708.0943), [Bibcode](/source/Bibcode_(identifier)):[2007AstL...33..571B](https://ui.adsabs.harvard.edu/abs/2007AstL...33..571B), [doi](/source/Doi_(identifier)):[10.1134/S1063773707090010](https://doi.org/10.1134%2FS1063773707090010), [S2CID](/source/S2CID_(identifier)) [15785349](https://api.semanticscholar.org/CorpusID:15785349).

v t e Constellation of Centaurus List of stars in Centaurus Centaurus in Chinese astronomy Stars Bayer α A (Rigil Kentaurus) B (Toliman) C (Proxima Centauri) β (Hadar) γ δ ε ζ (Leepwal) η θ (Menkent) ι (Kulou) κ λ μ ν (Heng) ξ1 ξ2 ο1 ο2 π ρ σ τ υ1 υ2 φ χ ψ x1 x2 C3 D E F G H J K M N Q Flamsteed 1 (i) 2 (g) 3 (k) 4 (h) Variable R T V Y RR SV SX BV DY UY V346 V553 V744 V752 V761 (a) V763 (C1) V766 V779 (Krzemiński's star) V803 V810 V816 (Przybylski's Star) V831 V842 V885 V886 V863 V1032 V1369 V1400 V1935 HR 4460 (A) 4466 (C2) 4499 4522 4523 4537 (j) 4546 (B) 4721 4748 (u) 4796 4817 (l) 4831 (w) 4874 (p) 4888 (e) 4889 (n) 4940 (f) 4979 4989 5006 (r) 5041 (m) 5089 (d) 5174 (z) 5222 (y) 5224 5241 5297 5358 (v) 5371 5471 (b) 5485 (c1) 5489 (c2) HD 97413 98176 100453 101581 101930 102117 (Uklun) 103197 107914 108236 109749 110113 113538 113766 114386 114729 115600 116434 (Matza) 117207 117618 (Dofida) 117939 120411 121228 121504 124448 (Popper's Star) 125072 125595 131399 Other 2MASS J1126−5003 2M1207 Gaia BH2 HD 131399 Ab PSR B1259−63 PSR J1311−3430 TOI-763 WASP-15 (Nyamien) WASP-41 WASP-42 WASP-167/KELT-13 Exoplanets 2M1207b b Centauri b HD 101930 b HD 102117 b (Leklsullun) HD 103197 b HD 109749 b HD 113538 b c HD 114386 b HD 114729 b HD 117207 b HD 117618 b (Noifasui) HD 121504 b HIP 65426 b (Najsakopajk) HIP 67522 b NGTS-13b Proxima Centauri b c d WASP-15b (Asye) Star clusters NGC 3766 4230 4507 5281 5286 5316 5460 5617 5662 Other IC 2944 ω Centauri Scorpius–Centaurus association Stock 16 Nebulae NGC 3918 5307 Other Boomerang Nebula Fleming 1 G292.0+1.8 G306.3-0.9 Gum 41 IC 2944 IRAS 13208−6020 RCW 79 RCW 86 Southern Crab Nebula SuWt 2 Galaxies NGC 3557 3568 3749 3783 4444 4603 4622 4650A 4683 4696 4706 4709 4729 4730 4743 4744 4909 4930 4945 4976 5011 A 5026 5064 5082 5090 5091 5102 5114 5121 5128 (Centaurus A) 5161 5206 5253 5266 5291 5398 5408 5419 5483 5516 Other ESO 269-57 ESO 325-4 ESO 383-76 ESO 444-46 Fourcade-Figueroa Object IC 3370 IC 4214 IC 4329A IRAS 13224−3809 J1144−4308 LEDA 677373 PKS 1144−379 PKS 1353−341 PKS 1424−418 Galaxy clusters Abell S740 Centaurus Cluster Shapley Supercluster Astronomical events GW190521 SN 185 SN 1895B (Z) SN 1972E SN 1986G J1407b SN 2019so Category

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Adapted from the Wikipedia article [Pi Centauri](https://en.wikipedia.org/wiki/Pi_Centauri) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Pi_Centauri?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.