Omicron1 Canis Majoris

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ο1 Canis Majoris
Canis Major constellation map.svg
Red circle.svg
Location of ο2 CMa (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Canis Major
Right ascension  06h 54m 07.95237s[1]
Declination −24° 11′ 03.1597″[1]
Apparent magnitude (V) 3.87[2] (3.78 - 3.99[3])
Spectral type K2.5 Iab[4]
U−B color index +1.99[2]
B−V color index +1.73[2]
Variable type Lc[3]
Radial velocity (Rv)+36.3[5] km/s
Proper motion (μ) RA: −3.83[1] mas/yr
Dec.: 4.98[1] mas/yr
Parallax (π)0.22 ± 0.43[1] mas
Distance610[6] pc
Absolute magnitude (MV)−4.69[4]
Mass7.83 ± 2.0[7] M
Radius280[4] R
Luminosity (bolometric)16,000[4] L
Surface gravity (log g)0.6[4] cgs
Temperature3,900[4] K
Metallicity [Fe/H]−0.11[8] dex
Rotational velocity (v sin i)12.31[9] km/s
Age18[10] Myr
Other designations
16 Canis Majoris, HR 2580, HD 50877, CD−24°4567, HIP 33152, SAO 172542, GC 9059
Database references

Omicron1 Canis Majoris (ο1 CMa, ο1 Canis Majoris) is a red supergiant star in the constellation Canis Major, it is a variable star in the constellation of Canis Major.


Johann Bayer gave two adjacent stars the Bayer designation of ο Canis Majoris in 1603, but without distinguishing between the stars. John Flamsteed gave the two omicron stars his own numbered designations of 16 and 24 Canis Majoris in the early 18th century.[11] Friedrich Wilhelm Argelander labelled the stars as ο1 and ο2 in his atlas Uranometria Nova.[12] Nicolas Louis de Lacaille labelled it c Canis Majoris, but this was not upheld by subsequent cartographers,[13] its Henry Draper Catalogue designation is HD 50877. The two Omicron stars marked the centre of the Great Dog's body on Bayer's 1603 Uranometria.[14]


The distance to ο1 Canis Majoris is uncertain, it is strongly associated with the Collinder 121 stellar association, located around 3,500 light years (1,085 parsecs) distant.[15] Its original Hipparcos parallax placed it at 610 pc, similar to the distance of EZ Canis Majoris, another member of Cr 121. ο1 CMa appears to be interacting with the nebula around EZ CMa, implying the two are at the same distance. However, the revised Hipparcos parallax is only 0.22 mas, with a margin of error of 0.43 mas, so the distance is not well-defined but likely to be large. The distance to EZ CMa is now thought to be around 1,500 pc. Conversely, though only separated by 2 degrees from the blue supergiant ο2 Canis Majoris, the two appear to be unrelated.[10]


The star itself is an orange K-type supergiant of spectral type K2.5 Iab and is an irregular variable star, varying between apparent magnitudes 3.78 and 3.99. A cool star, its surface temperature is around 3,900 K.[4] Around 8 times as massive as the Sun with around 280 times its diameter, it shines with 16,000 times its luminosity. Interstellar dust only obscures it slightly, and its apparent magnitude is 0.16 fainter than it would be if unobscured.[4] Thought to be around 18 million years old, ο1 Canis Majoris is undergoing nuclear fusion of helium in its core to generate energy and will one day explode as a type II supernova.[10]


  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 c Ducati, J. R. (2002). "VizieR Online Data Catalog: Catalogue of Stellar Photometry in Johnson's 11-color system". CDS/ADC Collection of Electronic Catalogues. 2237. Bibcode:2002yCat.2237....0D.
  3. ^ 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.
  4. ^ a b c d e f g h Levesque, E. M.; Massey, P.; Olsen, K. A. G.; Plez, B.; Josselin, E.; Maeder, A.; Meynet, G. (2005). "The Effective Temperature Scale of Galactic Red Supergiants: Cool, but Not as Cool as We Thought". The Astrophysical Journal. 628 (2): 973–985. arXiv:astro-ph/0504337. Bibcode:2005ApJ...628..973L. doi:10.1086/430901.
  5. ^ Evans, D. S. (1967). "The Revision of the General Catalogue of Radial Velocities". Determination of Radial Velocities and Their Applications. 30: 57. Bibcode:1967IAUS...30...57E.
  6. ^ Stencel, R. E.; Ueta, T.; Wall, R. J.; Yamamura, I. (2009). "Preliminary Study of Red Supergiant Star Membership in OB Star Associations of the Milky Way". AKARI. 418: 459. Bibcode:2009ASPC..418..459S.
  7. ^ Reffert, Sabine; Bergmann, Christoph; Quirrenbach, Andreas; Trifonov, Trifon; Künstler, Andreas (2015). "Precise radial velocities of giant stars. VII. Occurrence rate of giant extrasolar planets as a function of mass and metallicity". Astronomy & Astrophysics. 574: A116. arXiv:1412.4634. Bibcode:2015A&A...574A.116R. doi:10.1051/0004-6361/201322360. hdl:10722/215277.
  8. ^ Marrese, P. M.; Boschi, F.; Munari, U. (2003). "High resolution spectroscopy over lambda lambda 8500-8750 Å for GAIA. IV. Extending the cool MK stars sample". Astronomy and Astrophysics. 406 (3): 995. Bibcode:2003A&A...406..995M. doi:10.1051/0004-6361:20030647.
  9. ^ Hekker, S.; Meléndez, J. (2007). "Precise radial velocities of giant stars". Astronomy and Astrophysics. 475 (3): 1003. arXiv:0709.1145. Bibcode:2007A&A...475.1003H. doi:10.1051/0004-6361:20078233.
  10. ^ a b c Kaler, James B. "Omicron1 Canis Majoris". Stars. University of Illinois. Retrieved 24 February 2014.
  11. ^ John Flamsteed; Claudius Ptolemaeus; Tycho Brahe; Johannes Hevelius; Abraham Sharp (1725). Historia Coelestis Britannica: Complectens Praefationem spatiosam (sive in Stellarum Fixarum Catalogum Prolegomena) quae brevem Astronomiae Historiam praebet, atque Descriptionem Observationum peractarum, & Organorum adhibitorum tum a pristinis Astronomis, tum In Observatorio Regio Grenovicensi ; Deinceps Fixarum Catalogum a Ptolemaeo, Uleg Beig, Tychone Brahaeo, Gulielmo Hessiae Landtgravio, ac Hevelio constructum ... : Quibus adnexus est Fixarum quarundam Australium Catalogus, in nostro Hemisphaerio non adspectabilium, Denique Tabulae …. Meere. pp. 2–.
  12. ^ Argelander, Friedrich Wilhelm August (1843). Uranometria nova : stellae per mediam europam solis oculis conspicuae secundum veras lucis magnitudines e coelo ipso descriptae = Neue Uranometrie : Darstellung der im mittlern Europa mit blossen Augen sichtbaren Sterne nach ihren wahren, unmittelbar vom Himmel entnommenen Grössen / Fr. Argelander. Uranometria Nova : Stellae per Mediam Europam Solis Oculis Conspicuae Secundum Veras Lucis Magnitudines e Coelo Ipso Descriptae = Neue Uranometrie : Darstellung der Im Mittlern Europa Mit Blossen Augen Sichtbaren Sterne Nach Ihren Wahren. doi:10.3931/e-rara-559.
  13. ^ Wagman, Morton (2003). Lost Stars: Lost, Missing and Troublesome Stars from the Catalogues of Johannes Bayer, Nicholas Louis de Lacaille, John Flamsteed, and Sundry Others. Blacksburg, VA: The McDonald & Woodward Publishing Company. pp. 73–74. ISBN 978-0-939923-78-6.
  14. ^ Wagman, p. 504.
  15. ^ Kaltcheva, N. T. (2000). "The region of Collinder 121". Monthly Notices of the Royal Astronomical Society. 318 (4): 1023–35. Bibcode:2000MNRAS.318.1023K. doi:10.1046/j.1365-8711.2000.03689.x.