Omicron2 Orionis

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ο2 Orionis
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Orion
Right ascension 04h 56m 22.27612s[1]
Declination +13° 30′ 52.0932″[1]
Apparent magnitude (V) 4.06[2]
Spectral type K2 IIIb[3]
U−B color index +1.14[2]
B−V color index +1.17[2]
Radial velocity (Rv) 2.54±0.15[4] km/s
Proper motion (μ) RA: −74.88[1] mas/yr
Dec.: −44.33[1] mas/yr
Parallax (π) 17.54 ± 0.21[1] mas
Distance 186 ± 2 ly
(57.0 ± 0.7 pc)
Absolute magnitude (MV) 0.501[5]
Radius 15 R
Luminosity 79 L
Surface gravity (log g) 2.4 cgs
Temperature 4,498 K
Metallicity [Fe/H] −0.26 dex
Rotational velocity (v sin i) 0.0 km/s
Age 5.42±2.38[5] Gyr
Other designations
ο2 Ori, 9 Orionis, BD+13° 740, HD 31421, HIP 22957, HR 1580, SAO 94218.[6]
Database references

Omicron2 Orionis (ο2 Ori) is a solitary[7] star in the constellation Orion. It has an apparent visual magnitude of 4.06,[2] which is bright enough to be seen with the naked eye. Based upon an annual parallax shift of 17.54 mas, it is around 186 light years from the Sun. At that distance, the visual magnitude of the star is diminished by an interstellar absorption factor of 0.09 due to intervening dust.[8]

This is a red clump[5] giant star with a stellar classification of K2 IIIb.[3] It is around 5.4[5] billion years old with a projected rotational velocity that is too small to be measured. The star has expanded to about 15 times the radius of the Sun and shines with 79 times the solar luminosity from its outer atmosphere at an effective temperature of 4,498 K.[4] Omicron2 Orionis is most likely a member of the Milky Way's thin disk population.[5]


  1. ^ a b c d e 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 ^ a b c d Mermilliod, J.-C. (1986), "Compilation of Eggen's UBV data, transformed to UBV (unpublished)", Catalogue of Eggen's UBV data, SIMBAD, Bibcode:1986EgUBV........0M. 
  3. ^ a b Luck, R. Earle (September 2015), "Abundances in the Local Region. I. G and K Giants", The Astronomical Journal, 150 (3): 23, arXiv:1507.01466Freely accessible, Bibcode:2015AJ....150...88L, doi:10.1088/0004-6256/150/3/88, 88. 
  4. ^ a b c Massarotti, Alessandro; et al. (January 2008), "Rotational and radial velocities for a sample of 761 HIPPARCOS giants and the role of binarity", The Astronomical Journal, 135 (1): 209–231, Bibcode:2008AJ....135..209M, doi:10.1088/0004-6256/135/1/209. 
  5. ^ a b c d e Soubiran, C.; et al. (2008), "Vertical distribution of Galactic disk stars. IV. AMR and AVR from clump giants", Astronomy and Astrophysics, 480 (1): 91–101, arXiv:0712.1370Freely accessible, Bibcode:2008A&A...480...91S, doi:10.1051/0004-6361:20078788. 
  6. ^ "* omi02 Ori". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2016-11-14. 
  7. ^ 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. 
  8. ^ Famaey, B.; et al. (2005), "Local kinematics of K and M giants from CORAVEL/Hipparcos/Tycho-2 data. Revisiting the concept of superclusters", Astronomy and Astrophysics, 430: 165–186, arXiv:astro-ph/0409579Freely accessible, Bibcode:2005A&A...430..165F, doi:10.1051/0004-6361:20041272.