Sigma Canis Majoris

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σ Canis Majoris
Canis Major constellation map.svg
Red circle.svg

Location of σ Canis Majoris (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Canis Major
Right ascension 07h 01m 43.14779s[1]
Declination –27° 56′ 05.3898″[1]
Apparent magnitude (V) 3.43 - 3.51[2]
Spectral type K4 III[3]
U−B color index +1.88[4]
B−V color index +1.73[4]
Variable type LC[2]
Radial velocity (Rv) +22.11[5] km/s
Proper motion (μ) RA: –5.98[1] mas/yr
Dec.: +4.59[1] mas/yr
Parallax (π) 2.91 ± 0.19[1] mas
Distance 1,120 ± 70 ly
(340 ± 20 pc)
Absolute magnitude (MV) –5.14[6]
Mass 12.3 ± 0.1[7] M
Radius 420[6] R
Luminosity 31,000[6] L
Surface gravity (log g) 1.00[8] cgs
Temperature 3,750[6] K
Metallicity [Fe/H] +0.16[8] dex
Age 16.4 ± 0.5[7] Myr
Other designations
22 Canis Majoris, ADS 5719, CD −27° 3544, FK5 1183, HD 52877, HIP 33856, HR 2646, SAO 172797, Unurgunite.[9]
Database references

Sigma Canis Majoris (σ CMa, σ Canis Majoris) is a star in the southern constellation of Canis Major. It is approximately 1,120 light-years (340 parsecs) from Earth and has an average apparent visual magnitude of +3.41.


σ CMa is a supergiant star with a stellar classification of K4 III. This is a type of star that is in the late stages of its evolution, having consumed the hydrogen at its core and ballooned out to 420 times the Sun's radius.[6] At 1.95 Astronomical Units,[10] this radius is nearly double the average distance of the Earth from the Sun. It is currently radiating about 32,000[11] times the luminosity of the Sun from its outer envelope at an effective temperature of around 3,877 K.[8] This gives it the cool orange-red hue of an M-type star.[12]


σ CMa was noted as a likely variable star in a list of bright southern stars studied at the Cape Observatory.[13] The variability was confirmed in 1963,[14] and it was formally catalogued as a variable star.[15]

It is classified as an irregular variable star and its brightness varies from magnitude +3.43 to +3.51. The magnetic field of this star has a strength below 1 G.[16] It is suspected of being a member of the Collinder 121 stellar association of co-moving stars,[6] but this is disputed.[17]


σ CMa is listed as a possible type II supernova. Instruments are capable of measuring the pre-supernova neutrino flux which would act as an alert that the supernova explosion was starting.[18]

Culture signification[edit]

The indigenous Boorong people of northwestern Victoria saw it as Unurgunite, flanked by his wives (Epsilon and Delta Canis Majoris).[9]


  1. ^ a b c d e van Leeuwen, Floor (November 2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, arXiv:0708.1752v1Freely accessible, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357  Note: see VizieR catalogue I/311.
  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: 02025. Bibcode:2009yCat....102025S. 
  3. ^ Abt, Helmut A (2008). "Visual Multiples. IX. MK Spectral Types". The Astrophysical Journal Supplement Series. 176: 216–217. Bibcode:2008ApJS..176..216A. doi:10.1086/525529. 
  4. ^ a b 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: 0. Bibcode:2002yCat.2237....0D. 
  5. ^ Mermilliod, J. C.; Mayor, M.; Udry, S. (July 2008), "Red giants in open clusters. XIV. Mean radial velocities for 1309 stars and 166 open clusters", Astronomy and Astrophysics, 485 (1): 303–314, Bibcode:2008A&A...485..303M, doi:10.1051/0004-6361:200809664 
  6. ^ a b c d e f Levesque, Emily M.; et al. (August 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/0504337Freely accessible, Bibcode:2005ApJ...628..973L, doi:10.1086/430901 
  7. ^ a b Tetzlaff, N.; Neuhäuser, R.; Hohle, M. M. (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 
  8. ^ a b c Mallik, Sushma V. (October 1998), "Chromospheric activity in cool stars and the lithium abundance", Astronomy and Astrophysics, 338: 623–636, Bibcode:1998A&A...338..623M 
  9. ^ a b Hamacher, Duane W.; Frew, David J. (2010). "An Aboriginal Australian Record of the Great Eruption of Eta Carinae" (PDF). Journal of Astronomical History & Heritage. 13 (3): 220–34. arXiv:1010.4610Freely accessible. Bibcode:2010JAHH...13..220H. 
  10. ^ 1 solar radius = 0.0046491 Astronomical Units, so 420 × 0.00465 = 1.95.
  11. ^ Mallik, Sushma V. (December 1999), "Lithium abundance and mass", Astronomy and Astrophysics, 352: 495–507, Bibcode:1999A&A...352..495M 
  12. ^ "The Colour of Stars", Australia Telescope, Outreach and Education, Commonwealth Scientific and Industrial Research Organisation, December 21, 2004, retrieved 2012-01-16 
  13. ^ Cousins, A. W. J. (1951). "Bright variable stars in southern hemisphere (first list)". The Observatory. 71: 199. Bibcode:1951Obs....71..199C. 
  14. ^ Cousins, A. W. J. (1963). "Red Variable Stars of Small Range Amongst the Bright Stars". Monthly Notes of the Astron. Soc. Southern Africa. 22: 133. Bibcode:1963MNSSA..22..133C. 
  15. ^ Kukarkin, B. V.; Kholopov, P. N.; Kukarkina, N. P.; Perova, N. B. (1973). "59th Name-List of Variable Stars". Information Bulletin on Variable Stars. 834: 1. Bibcode:1973IBVS..834....1K. 
  16. ^ Grunhut, J. H.; et al. (November 2010), "Systematic detection of magnetic fields in massive, late-type supergiants", Monthly Notices of the Royal Astronomical Society, 408 (4): 2290–2297, arXiv:1006.5891Freely accessible, Bibcode:2010MNRAS.408.2290G, doi:10.1111/j.1365-2966.2010.17275.x 
  17. ^ de Zeeuw, P. T.; et al. (January 1999), "A HIPPARCOS Census of the Nearby OB Associations", The Astronomical Journal, 117 (1): 354–399, arXiv:astro-ph/9809227Freely accessible, Bibcode:1999AJ....117..354D, doi:10.1086/300682 
  18. ^ Asakura, K.; Gando, A.; Gando, Y.; Hachiya, T.; Hayashida, S.; Ikeda, H.; Inoue, K.; Ishidoshiro, K.; Ishikawa, T.; Ishio, S.; Koga, M.; Matsuda, S.; Mitsui, T.; Motoki, D.; Nakamura, K.; Obara, S.; Oura, T.; Shimizu, I.; Shirahata, Y.; Shirai, J.; Suzuki, A.; Tachibana, H.; Tamae, K.; Ueshima, K.; Watanabe, H.; Xu, B. D.; Kozlov, A.; Takemoto, Y.; Yoshida, S.; et al. (2016). "KamLAND Sensitivity to Neutrinos from Pre-supernova Stars". The Astrophysical Journal. 818: 91. arXiv:1506.01175Freely accessible. Bibcode:2016ApJ...818...91A. doi:10.3847/0004-637X/818/1/91.