Omicron1 Orionis

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ο1 Orionis
Orion constellation map.svg
Red circle.svg
Location of ο1 Orionis (circled)
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Orion
Right ascension  04h 52m 31.96357s[1]
Declination +14° 15′ 02.3215″[1]
Apparent magnitude (V) 4.65 - 4.88[2]
Spectral type M3S III[3]
U−B color index +2.03[4]
B−V color index +1.74[4]
Variable type SRb[2]
Radial velocity (Rv)−8.40±0.23[5] km/s
Proper motion (μ) RA: −0.05[1] mas/yr
Dec.: −54.81[1] mas/yr
Parallax (π)5.01 ± 0.71[1] mas
Distanceapprox. 650 ly
(approx. 200 pc)
Mass0.9[6] M
Radius214±29[6] R
Luminosity4,046[7] L
Surface gravity (log g)0.76±0.29[8] cgs
Temperature3,465±27[8] K
Metallicity [Fe/H]−0.03±0.12[8] dex
Other designations
ο1 Ori, 4 Orionis, BD+14 777, FK5 1136, HD 30959, HIP 22667, HR 1556, SAO 94176
Database references

Omicron1 Orionis (ο1 Ori) is a binary star[9] in the northeastern corner of the constellation Orion. It is visible to the naked eye with an apparent visual magnitude of 4.7.[4] Based upon an annual parallax shift of 5.01±0.71 mas, it is located approximately 650 light years from the Sun. At that distance, the visual magnitude of the star is diminished by an interstellar absorption factor of 0.27 due to intervening dust.[5]

The two components of this system have an orbital period of greater than 1,900 days (5.2 years).[9] The primary component is an evolved red giant with the stellar classification of M3S III. This is an S-type star on the asymptotic giant branch.[3] It is a semiregular variable[10] that is pulsating with periods of 30.8 and 70.7 days, each with nearly identical amplitudes of 0.05 in magnitude.[11] The star has an estimated 90% of the mass of the Sun but has expanded to 214 times the Sun's radius.[6] It shines with 4,046[7] times the solar luminosity from its outer atmosphere at an effective temperature of 3,465 K.[8]


  1. ^ a b c d e van Leeuwen, F. (2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, arXiv:0708.1752, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357.
  2. ^ a b Samus, N. N.; Durlevich, O. V.; et al. (2009). "VizieR Online Data Catalog: General Catalogue of Variable Stars (Samus+ 2007-2013)". VizieR On-line Data Catalog: B/gcvs. Originally Published in: 2009yCat....102025S. 1. Bibcode:2009yCat....102025S.
  3. ^ a b Cox, N. L. J.; et al. (January 2012), "A far-infrared survey of bow shocks and detached shells around AGB stars and red supergiants", Astronomy & Astrophysics, 537: 28, arXiv:1110.5486, Bibcode:2012A&A...537A..35C, doi:10.1051/0004-6361/201117910, A35.
  4. ^ a b c Mermilliod, J.-C. (1986), "Compilation of Eggen's UBV data, transformed to UBV (unpublished)", Catalogue of Eggen's UBV Data, SIMBAD, Bibcode:1986EgUBV........0M.
  5. ^ a b Famaey, B.; et al. (January 2005), "Local kinematics of K and M giants from CORAVEL/Hipparcos/Tycho-2 data. Revisiting the concept of superclusters", Astronomy and Astrophysics, 430 (1): 165–186, arXiv:astro-ph/0409579, Bibcode:2005A&A...430..165F, doi:10.1051/0004-6361:20041272.
  6. ^ a b c Cruzalèbes, P.; Jorissen, A.; Rabbia, Y.; Sacuto, S.; Chiavassa, A.; Pasquato, E.; Plez, B.; Eriksson, K.; Spang, A.; Chesneau, O. (2013), "Fundamental parameters of 16 late-type stars derived from their angular diameter measured with VLTI/AMBER", Monthly Notices of the Royal Astronomical Society, 434: 437–450, arXiv:1306.3288, Bibcode:2013MNRAS.434..437C, doi:10.1093/mnras/stt1037.
  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:1208.2037, Bibcode:2012MNRAS.427..343M, doi:10.1111/j.1365-2966.2012.21873.x.
  8. ^ a b c d Prugniel, Ph.; et al. (July 2011), "The atmospheric parameters and spectral interpolator for the MILES stars", Astronomy & Astrophysics, 531: A165, arXiv:1104.4952, Bibcode:2011A&A...531A.165P, doi:10.1051/0004-6361/201116769.
  9. ^ a b Udry, S.; Jorissen, A.; Mayor, M.; Van Eck, S. (July 1998), "A CORAVEL radial-velocity monitoring of giant BA and S stars: Spectroscopic orbits and intrinsic variations. I.", Astronomy and Astrophysics Supplement, 131: 25–41, arXiv:astro-ph/9801273, Bibcode:1998A&AS..131...25U, doi:10.1051/aas:1998249.
  10. ^ Glass, I. S.; Van Leeuwen, F. (2007), "Semiregular variables in the solar neighbourhood", Monthly Notices of the Royal Astronomical Society, 378 (4): 1543–1549, arXiv:0704.3150, Bibcode:2007MNRAS.378.1543G, doi:10.1111/j.1365-2966.2007.11903.x.
  11. ^ Tabur, V.; et al. (December 2009), "Long-term photometry and periods for 261 nearby pulsating M giants", Monthly Notices of the Royal Astronomical Society, 400 (4): 1945–1961, arXiv:0908.3228, Bibcode:2009MNRAS.400.1945T, doi:10.1111/j.1365-2966.2009.15588.x.