Pi Centauri
{{Short description|Star in the constellation Centaurus}}
{{Starbox begin}}
{{Starbox observe
| epoch = J2000.0
| constell = Centaurus
| appmag_v = +3.90 {{nowrap|(4.08 + 5.65)}}
}}
{{Starbox character
| type =
| class = B5Vn + B6V
| u-b =
| variable =
}}
{{Starbox astrometry
| prop_mo_ra = {{Val|−35.85|0.34}}
| prop_mo_dec = {{Val|−1.72|0.27}}
| parallax = 9.12
| p_error = 0.34
}}
{{Starbox orbit
| period = {{Val|39.0|0.19}}
| axis = {{Val|0.2263|0.0011}}
| eccentricity = {{Val|0.8530|0.0040}}
| inclination = {{Val|19.4|4.9}}
| node = {{Val|327.8|3.9}}
| periastron = {{Val|2010.410|0.037}}
| periarg = {{Val|340.3|4.0}}
}}
{{Starbox detail
| source =
| component1 = A
| radius =
| gravity =
| metal_fe =
| age_myr =
| component2 = B
}}
{{Starbox catalog
| names = {{odlist | B=π Cen | BD=−53°4498 | FK5=428 | HD=98718 | HIP=55425 | HR=4390 | SAO=238986 | CCDM=J11210-5429 | GC=15601 }}
}}
{{Starbox reference
| Simbad = pi+Cen
}}
{{Starbox end}}
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. The system is located at a distance of approximately 360 light years from the Sun based on parallax, and is drifting further away with a radial velocity of around +9 km/s. It is a member of the Lower Centaurus–Crux subgroup of the Scorpius–Centaurus association.
The magnitude +4.08 primary, designated component A, is a B-type main-sequence star with a stellar classification of B5Vn, 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. It has 6.4 times the mass of the Sun and is radiating 783 times the Sun's luminosity from its photosphere at an effective temperature of 16,760 K.
The secondary companion, component B, is magnitude +5.65 with a class of B6V and 3.7 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°.
References
{{Reflist|refs=
| title=pi Cen | access-date=2019-10-10 }}
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| bibcode=2009A&A...501..297Z | arxiv=0903.5134 | s2cid=14969137 }}
| title=MK classification for visual binary components
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| bibcode=1976AJ.....81..245E | doi=10.1086/111879 }}
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| journal=The Astronomical Journal | postscript=.
| volume=122 | issue=6 | pages=3466 | year=2001
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| journal=Astronomy and Astrophysics
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| arxiv=0708.1752 | bibcode=2007A&A...474..653V
| doi=10.1051/0004-6361:20078357 | s2cid=18759600 | postscript=. }}[http://webviz.u-strasbg.fr/viz-bin/VizieR-5?-out.add=.&-source=I/311/hip2&recno=55246 Vizier catalog entry ]
}}
{{Stars of Centaurus}}
{{DEFAULTSORT:Pi Centauri}}
Category:B-type main-sequence stars