Mu Canis Majoris

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Mu Canis Majoris
Canis Major constellation map.svg
Red circle.svg
Location of μ Canis Majoris (circled)
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Canis Major
Right ascension 06h 56m 06.64589s[1]
Declination −14° 02′ 36.3520″[1]
Apparent magnitude (V) 5.12 (5.27 + 7.32)[2]
Spectral type K2/3 III + B9/A0 V[3]
Radial velocity (Rv)18.1±0.1[4] km/s
Proper motion (μ) RA: −1.59[1] mas/yr
Dec.: + 6.33[1] mas/yr
Parallax (π)2.62 ± 0.58[1] mas
Distanceapprox. 1,200 ly
(approx. 380 pc)
Absolute magnitude (MV)−2.22[5]
μ CMa A
Surface gravity (log g)2489[6] cgs
Temperature4,441[6] K
Rotational velocity (v sin i)≤ 5[7] km/s
μ CMa B
Mass14.7±0.3[8] M
Age11.6±0.5[8] Myr
Other designations
μ CMa, 18 CMa, BD−13° 1741, HIP 33345, HR 2593, SAO 152123[9]
μ CMa A: HD 51250[9]
μ CMa B: HD 51251[10]
Database references

Mu Canis Majoris (μ Canis Majoris) is a binary star[2] system in the southern constellation of Canis Major. The pair can be located a little to the southwest of the point midway between Gamma and Theta Canis Majoris,[11] and the components can be split with a small telescope.[12] The system is faintly visible to the naked eye with an apparent visual magnitude of 5.12.[2] Based upon an annual parallax shift of just 2.62 mas as seen from Earth,[1] this system is located roughly 1,200 light years from the Sun.

Grotius assigned the name Isis to this star, but the name, now obsolete, belonged rather to Gamma Canis Majoris.[13]

As of 2011, the pair had an angular separation of 2.77 arc seconds along a position angle of 343.9°.[14] The orange-hued primary member, component A, is an evolved K-type giant star with a stellar classification of K2/3 III[3] and a visual magnitude of 5.27.[2] The base magnitude 7.32[2] companion, component B, is a hybrid B/A-type main-sequence star with a class of B9/A0 V.[3]

The system has two visual companions. As of 2008, magnitude 10.32 component C lies at an angular separation of 86.90″, while magnitude 10.64 component D is at a separation of 105.0″.[15] Mu CMa should not be confused with the 9th magnitude variable star MU CMa located near NGC 2360.[16]


  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 e 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. 
  3. ^ a b c Houk, Nancy; Smith-Moore, M. (1978), Michigan catalogue of two-dimensional spectral types for the HD stars, 4, Ann Arbor: Dept. of Astronomy, University of Michigan, 
  4. ^ de Bruijne, J. H. J.; Eilers, A.-C. (October 2012), "Radial velocities for the HIPPARCOS-Gaia Hundred-Thousand-Proper-Motion project", Astronomy & Astrophysics, 546: 14, arXiv:1208.3048Freely accessible, Bibcode:2012A&A...546A..61D, doi:10.1051/0004-6361/201219219, A61. 
  5. ^ Ginestet, N.; Carquillat, J. M. (2002), "Spectral Classification of the Hot Components of a Large Sample of Stars with Composite Spectra, and Implication for the Absolute Magnitudes of the Cool Supergiant Components", The Astrophysical Journal Supplement Series, 143 (2): 513, Bibcode:2002ApJS..143..513G, doi:10.1086/342942. 
  6. ^ 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. 
  7. ^ Eaton, J. A. (May 1990), "Rotational Velocities of G and K Giants", Information Bulletin on Variable Stars, 3460: 1, Bibcode:1990IBVS.3460....1E. 
  8. ^ a b Tetzlaff, N.; et al. (January 2011), "A catalogue of young runaway Hipparcos stars within 3 kpc from the Sun", Monthly Notices of the Royal Astronomical Society, 410 (1): 190–200, arXiv:1007.4883Freely accessible, Bibcode:2011MNRAS.410..190T, doi:10.1111/j.1365-2966.2010.17434.x. 
  9. ^ a b "mu. CMa". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2017-09-07. 
  10. ^ "HD 51251". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2017-09-07. 
  11. ^ O'Meara, Steve (2007), Herschel 400 Observing Guide, Cambridge University Press, p. 63, ISBN 0521858933. 
  12. ^ Consolmagno, Guy (2011), Turn Left at Orion: Hundreds of Night Sky Objects to See in a Home Telescope – and How to Find Them, Cambridge, United Kingdom: Cambridge University Press, p. 81, ISBN 1-139-50373-1. 
  13. ^ Richard Hinckley Allen (1963-06-01). Star Names: Their Lore and Meaning. Dover Publications. ISBN 978-0486210797. 
  14. ^ Mason, Brian D.; et al. (May 2012), "Speckle Interferometry at the U.S. Naval Observatory. XVIII", The Astronomical Journal, 143 (5): 6, Bibcode:2012AJ....143..124M, doi:10.1088/0004-6256/143/5/124, 124. 
  15. ^ Mason, B. D.; et al. (2014), The Washington Visual Double Star Catalog, Bibcode:2001AJ....122.3466M, doi:10.1086/323920. 
  16. ^ "International variable star Index: MU CMa". AAVSO. Retrieved 2012-06-03. 

External links[edit]