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Pi2 Orionis

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(Redirected from 2 Orionis) Star in the constellation Orion For other stars with this Bayer designation, see Pi Orionis.

π Orionis
Observation data Epoch J2000.0 Equinox J2000.0 (ICRS)
Location of π Orionis (circled)
Constellation	Orion
Right ascension	04 50 36.72298
Declination	+08° 54′ 00.6493″
Apparent magnitude (V)	4.35
Characteristics
Spectral type	A1 Vn
U−B color index	+0.03
B−V color index	+0.01
Astrometry

Radial velocity (R_v)	24 km/s
Proper motion (μ)	RA: +1.41 mas/yr Dec.: −29.91 mas/yr
Parallax (π)	14.53 ± 0.38 mas
Distance	224 ± 6 ly (69 ± 2 pc)
Absolute magnitude (M_V)	0.48

Details

Radius	2.7 `R`_☉
Luminosity	70 `L`_☉
Surface gravity (log g)	4.00±0.05 cgs
Temperature	9,457±128 K
Metallicity	−0.20±0.10 dex
Rotational velocity (v sin i)	261.4±13.5 km/s

Other designations
π Ori, 2 Orionis, BD+08°777, HD 30739, HIP 22509, HR 1544, SAO 112124
Database references
SIMBAD	data

Pi Orionis (π Ori, π Orionis) is the Bayer designation for a solitary star in the equatorial constellation of Orion. Although the Bright Star Catalogue lists this as a spectroscopic binary star system, this does not appear to be the case. It is visible to the naked eye with an apparent visual magnitude of 4.35. Based upon an annual parallax shift of 14.53 mas, it is located roughly 224 light-years away from the Sun.

This is an A-type main-sequence star with a stellar classification of A1 Vn, where the 'n' indicates broad absorption lines due to rotation. It is spinning rapidly with a projected rotational velocity of 261.4 km/s. This is giving the star an oblate shape with an equatorial bulge that is 13% larger than the polar radius. It is shining with 70 times the solar luminosity from its outer atmosphere at an effective temperature of 9,457 K.

References

^ van Leeuwen, F. (2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, arXiv:0708.1752, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357, S2CID 18759600.
^ Johnson, H. L.; et al. (1966), "UBVRIJKL photometry of the bright stars", Communications of the Lunar and Planetary Laboratory, 4 (99): 99, Bibcode:1966CoLPL...4...99J.
^ Cowley, A.; et al. (April 1969), "A study of the bright A stars. I. A catalogue of spectral classifications", Astronomical Journal, 74: 375–406, Bibcode:1969AJ.....74..375C, doi:10.1086/110819.
Wilson, R. E. (1953), "General Catalogue of Stellar Radial Velocities", Washington, Carnegie Institute of Washington, D.C., Bibcode:1953GCRV..C......0W.
^ Ammler-von Eiff, Matthias; Reiners, Ansgar (June 2012), "New measurements of rotation and differential rotation in A-F stars: are there two populations of differentially rotating stars?", Astronomy & Astrophysics, 542: A116, arXiv:1204.2459, Bibcode:2012A&A...542A.116A, doi:10.1051/0004-6361/201118724, S2CID 53666672.
Pasinetti Fracassini, L. E.; et al. (February 2001), "Catalogue of Apparent Diameters and Absolute Radii of Stars (CADARS) - Third edition - Comments and statistics", Astronomy and Astrophysics, 367 (2): 521–524, arXiv:astro-ph/0012289, Bibcode:2001A&A...367..521P, doi:10.1051/0004-6361:20000451, S2CID 425754.
^ McDonald, I.; et al. (2012), "Fundamental Parameters and Infrared Excesses of Hipparcos Stars", Monthly Notices of the Royal Astronomical Society, 427 (1): 343–57, arXiv:1208.2037, Bibcode:2012MNRAS.427..343M, doi:10.1111/j.1365-2966.2012.21873.x, S2CID 118665352.
^ Wu, Yue; et al. (January 2011), "Coudé-feed stellar spectral library - atmospheric parameters", Astronomy and Astrophysics, 525: A71, arXiv:1009.1491, Bibcode:2011A&A...525A..71W, doi:10.1051/0004-6361/201015014, S2CID 53480665.
"pi.02 Ori". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2016-11-16.
Hoffleit, Dorrit (1964), Catalogue of Bright Stars (3rd ed.), New Haven, Conn: Yale University Observatory, Bibcode:1964cbs..book.....H.
Eggleton, P. P.; Tokovinin, A. A. (September 2008), "A catalogue of multiplicity among bright stellar systems", Monthly Notices of the Royal Astronomical Society, 389 (2): 869–879, arXiv:0806.2878, Bibcode:2008MNRAS.389..869E, doi:10.1111/j.1365-2966.2008.13596.x, S2CID 14878976.
Belle, G. T. (2012), "Interferometric observations of rapidly rotating stars", The Astronomy and Astrophysics Review, 20 (1): 51, arXiv:1204.2572, Bibcode:2012A&ARv..20...51V, doi:10.1007/s00159-012-0051-2, S2CID 119273474.

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Constellation of Orion

Bayer	α (Betelgeuse) β (Rigel) γ (Bellatrix) δ (Mintaka) ε (Alnilam) ζ (Alnitak) η (Algjebba) θ A B C D E F G H θ ι (Hatysa) κ (Saiph) λ (Meissa) μ ν ξ ο ο π π π (Tabit) π π π ρ σ τ υ (Thabit) φ φ χ χ ψ ψ ω
Flamsteed	5 6 (g) 11 13 14 (i) 15 16 (h) 18 21 22 (o) 23 (m) 27 (p) 29 (e) 31 32 (A) 33 35 38 42 (c) 45 49 (d) 51 (b) 52 55 56 57 59 60 63 64 66 68 69 (f) 71 72 (f) 73 74 (k) 75 (l)
Variable	S U W UX VV BF BM DN FU GW V380 V883 V1005 V1149 V1201 V1352 V2247 V2254 V2384
HR	1759 1763 1874 1887 1952 1988 2007 2024 2251 2275
HD	33636 34445 37320 37605 42618 43317 290327
Other	4U 0614+091 CVSO 30 CWISE J0506+0738 Gliese 179 Gliese 205 Gliese 208 Gliese 221 GJ 3379 HOPS 383 LP 658-2 PDS 110 S Ori 52 S Ori 70 WISE J0457−0207 WISE J0521+1025

Exoplanets	HD 34445 b HD 37605 b HD 38529 b HD 290327 b

NGC	1662 1980 1981 2169 2175 2194 2202
Other	Lambda Orionis Cluster Trapezium Cluster (θ)

NGC	1788 1999 2022 2023 2064 2067 2071 2174
Other	Abell 12 Abell 13 Barnard 30 Becklin–Neugebauer Object Flame Nebula HH 1/2 HH 24-26 HH 34 HH 111 Horsehead Nebula IC 434 IC 2118 LDN 1641 McNeil's Nebula Messier 43 Messier 78 Orion Nebula

NGC	1683 1819 1924 2110 2119
Other	4C +09.17 CGCG 396-2 II Zwicky 28 PKS 0458-020 PKS 0528+134 TXS 0506+056

Astronomical events	GRB 991216