Chi2 Orionis

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χ2 Orionis
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Orion
Right ascension 06h 03m 55.18482s[1]
Declination +20° 08′ 18.4316″[1]
Apparent magnitude (V) 4.646[2]
Spectral type B2Iaev[2]
U−B color index −0.68[3]
B−V color index +0.28[3]
R−I color index +0.22[3]
Variable type alpha Cygni[4]
Radial velocity (Rv) 16.8 ± 0.9[2] km/s
Proper motion (μ) RA: 1.88[1] mas/yr
Dec.: −2.10[1] mas/yr
Parallax (π) 1.81 ± 0.28 mas
Distance approx. 1,800 ly
(approx. 550 pc)
Absolute magnitude (MV) -7.6[5]
Mass 42.3 ± 1.0[6] M
Radius 61.9[5] R
Surface gravity (log g) 2.35[5] cgs
Temperature 19,000[5] K
Rotational velocity (v sin i) 72[5] km/s
Age 5 ± 0.6[6] Myr
Other designations
χ2 Ori, Chi2 Orionis, Chi2 Ori, 62 Orionis, 62 Ori, BD+20 1233, GC 7675, HD 41117, HIP 28716, HR 2135, PPM 95316, SAO 77911.[2]
Database references

Chi2 Orionis (Chi2 Ori / χ2 Orionis / χ2 Ori) is a B-type supergiant star in the constellation of Orion.[2] It has an apparent visual magnitude of approximately 4.646.[2] Since 1943, the spectrum of this star has served as one of the stable anchor points by which other stars are classified.[7]


  1. ^ a b c d van Leeuwen, F. (November 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. 
  2. ^ a b c d e f * 62 Ori -- Emission-line Star, database entry, SIMBAD. Accessed on line January 14, 2011.
  3. ^ a b c HR 2135, database entry, The Bright Star Catalogue, 5th Revised Ed. (Preliminary Version), D. Hoffleit and W. H. Warren, Jr., CDS ID V/50. Accessed on line January 14, 2011.
  4. ^ khi 2 Ori, database entry, The combined table of GCVS Vols I-III and NL 67-78 with improved coordinates, General Catalogue of Variable Stars, Sternberg Astronomical Institute, Moscow, Russia. Accessed on line January 14, 2011.
  5. ^ a b c d e Crowther, P. A.; Lennon, D. J.; Walborn, N. R. (2006). "Physical parameters and wind properties of galactic early B supergiants". Astronomy and Astrophysics 446: 279. arXiv:astro-ph/0509436. Bibcode:2006A&A...446..279C. doi:10.1051/0004-6361:20053685.  edit
  6. ^ a b Tetzlaff, N.; Neuhäuser, R.; Hohle, M. M. (2011). "A catalogue of young runaway Hipparcos stars within 3 kpc from the Sun". Monthly Notices of the Royal Astronomical Society 410: 190. arXiv:1007.4883. Bibcode:2011MNRAS.410..190T. doi:10.1111/j.1365-2966.2010.17434.x.  edit
  7. ^ Garrison, R. F. (December 1993), "Anchor Points for the MK System of Spectral Classification", Bulletin of the American Astronomical Society 25: 1319, Bibcode:1993AAS...183.1710G, retrieved 2012-02-04