Pi2 Orionis

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For other stars with this Bayer designation, see Pi Orionis.
π2 Orionis
Orion constellation map.svg
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The location of Pi2 Orionis (π2) in the constellation of Orion (shown as a red circle with a red center, above π3).
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Orion
Right ascension 04h 50m 36.72298s[1]
Declination +08° 54′ 00.6493″[1]
Apparent magnitude (V) 4.35[2]
Spectral type A1 Vn[3]
U−B color index +0.03[2]
B−V color index +0.01[2]
Radial velocity (Rv) 24[4] km/s
Proper motion (μ) RA: +1.41[1] mas/yr
Dec.: −29.91[1] mas/yr
Parallax (π) 14.53 ± 0.38[1] mas
Distance 224 ± 6 ly
(69 ± 2 pc)
Absolute magnitude (MV) 0.48[5]
Radius 2.7[6] R
Luminosity 70[7] L
Surface gravity (log g) 4.00±0.05[8] cgs
Temperature 9,457±128[8] K
Metallicity [Fe/H] −0.20±0.10[8] dex
Rotational velocity (v sin i) 261.4±13.5[5] km/s
Other designations
π2 Ori, 2 Orionis, BD+08° 777, HD 30739, HIP 22509, HR 1544, SAO 112124.[9]
Database references

Pi2 Orionis2 Ori, π2 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,[10] this does not appear to be the case.[11] It is visible to the naked eye with an apparent visual magnitude of 4.35.[2] Based upon an annual parallax shift of 14.53 mas,[1] 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,[3] where the 'n' indicates broad absorption lines due to rotation. It is spinning rapidly with a projected rotational velocity of 261.4 km/s.[5] This is giving the star an oblate shape with an equator that is 13% larger than the polar radius.[12] It is shining with 70[7] times the solar luminosity from its outer atmosphere at an effective temperature of 9,457 K.[8]


  1. ^ a b c d e f van Leeuwen, F. (2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, arXiv:0708.1752Freely accessible, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357. 
  2. ^ a b c d Johnson, H. L.; et al. (1966), "UBVRIJKL photometry of the bright stars", Communications of the Lunar and Planetary Laboratory, 4 (99), Bibcode:1966CoLPL...4...99J. 
  3. ^ a b 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. 
  4. ^ Wilson, R. E. (1953), "General Catalogue of Stellar Radial Velocities", Washington, Carnegie Institute of Washington, D.C., Bibcode:1953GCRV..C......0W. 
  5. ^ a b c Ammler-von Eiff, M.; Reiners, A. (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:1204.2459Freely accessible, Bibcode:2012A&A...542A.116A, doi:10.1051/0004-6361/201118724. 
  6. ^ 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: 521–524, arXiv:astro-ph/0012289Freely accessible, Bibcode:2001A&A...367..521P, doi:10.1051/0004-6361:20000451. 
  7. ^ a b 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:1208.2037Freely accessible, Bibcode:2012MNRAS.427..343M, doi:10.1111/j.1365-2966.2012.21873.x. 
  8. ^ a b c d Wu, Yue; et al. (January 2011), "Coudé-feed stellar spectral library - atmospheric parameters", Astronomy and Astrophysics, 525: A71, arXiv:1009.1491Freely accessible, Bibcode:2011A&A...525A..71W, doi:10.1051/0004-6361/201015014. 
  9. ^ "pi.02 Ori -- Star", SIMBAD Astronomical Database, Centre de Données astronomiques de Strasbourg, retrieved 2016-11-16. 
  10. ^ Hoffleit, Dorrit (1964), Catalogue of Bright Stars (3rd ed.), New Haven, Conn: Yale University Observatory, Bibcode:1964cbs..book.....H. 
  11. ^ 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:0806.2878Freely accessible, Bibcode:2008MNRAS.389..869E, doi:10.1111/j.1365-2966.2008.13596.x. 
  12. ^ Belle, G. T. (2012), "Interferometric observations of rapidly rotating stars", The Astronomy and Astrophysics Review, 20: 51, arXiv:1204.2572Freely accessible, Bibcode:2012A&ARv..20...51V, doi:10.1007/s00159-012-0051-2.