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W Canis Majoris
	; A visual band light curve for W Canis Majoris, plotted from All Sky Automated Survey data.
Observation data; Epoch J2000.0 Equinox J2000.0 (ICRS)
Constellation	Canis Major
Right ascension	07h 08m 03.43652s
Declination	−11° 55′ 23.7977″
Apparent magnitude (V)	6.35–7.90
Characteristics
Spectral type	C6,3(N)
B−V color index	+2.55
Variable type	Lb
Astrometry
Radial velocity (Rv)	23.00 km/s
Proper motion (μ)	RA: −6.518 mas/yr ; Dec.: 2.280 mas/yr
Parallax (π)	1.8049 ± 0.1454 mas
Distance	1,800 ± 100 ly ; (550 ± 40 pc)
Details
Radius	234 R☉
Luminosity	2,900 L☉
Surface gravity (log g)	0.0 cgs
Temperature	2,900 K
Other designations
	W CMa, BD−11° 1805, HIP 34413, HD 54361, SAO 152427
Database references
SIMBAD	data

W Canis Majoris (W CMa) is a carbon star in the constellation Canis Major. A cool star, it has a surface temperature of around 2,900 K^[9] and a radius 234 times that of the Sun,^[8] with a bolometric absolute magnitude of −4.13 and distance estimated at 443 or 445 parsecs (1,444–1,450 light-years) based on bolometric magnitude or radius. The Gaia Data Release 2 parallax of 1.8049±0.1454 milliarcseconds implies a distance of about 555 parsecs. It is a variable star, whose brightness ranges from magnitude 6.35 to 7.90. At its brightest, it might be very faintly visible to the naked eye of an observer with ideal observing conditions.

In 1901, it was announced that Williamina Fleming had discovered the star, then called BD −11° 1805, is a variable star.^[10] It was given its variable star designation, W Canis Majoris, in 1912.^[11] W CMa is classified as a slow irregular variable star. Detailed analyses have found only very weak and probably spurious periods of approximately a month.^[5] It is a carbon star, an asymptotic giant branch star where carbon and s-process elements have been dredged up to the surface during thermal pulses of the helium-burning shell.^[12]

References

^ "ASAS All Star Catalogue". The All Sky Automated Survey. Retrieved 8 December 2021.
^ ^a ^b ^c ^d 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. S2CID 18759600.
^ ^a ^b ^c 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.
^ Alksnis, A.; Balklavs, A.; Dzervitis, U.; Eglitis, I. (1998). "Absolute magnitudes of carbon stars from HIPPARCOS parallaxes". Astronomy and Astrophysics. 338: 209. Bibcode:1998A&A...338..209A.
^ ^a ^b Percy, J. R.; Terziev, E. (2011). "Studies of "Irregularity" in Pulsating Red Giants. III. Many More Stars, an Overview, and Some Conclusions". The Journal of the American Association of Variable Star Observers. 39 (1): 1. Bibcode:2011JAVSO..39....1P.
^ Gontcharov, G. A. (2006). "Pulkovo Compilation of Radial Velocities for 35 495 Hipparcos stars in a common system". Astronomy Letters. 32 (11): 759–771. arXiv:1606.08053. Bibcode:2006AstL...32..759G. doi:10.1134/S1063773706110065. S2CID 119231169.
^ Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR.
^ ^a ^b ^c ^d van Belle, Gerard T.; Paladini, Claudia; Aringer, Bernhard; Hron, Josef; et al. (2013). "The PTI Carbon Star Angular Size Survey: Effective Temperatures and Non-sphericity". The Astrophysical Journal. 775 (1): article id. 45, 19 pp. arXiv:1307.6585. Bibcode:2013ApJ...775...45V. doi:10.1088/0004-637X/775/1/45. S2CID 43847096.
^ ^a ^b ^c Siderud, Emelie (2020). Dust emission modelling of AGB stars.
^ Pickering, E. C.; Colson, H. R.; Fleming, W. P.; Wells, L. D. (April 1901). "Sixty-four new variable stars". Astrophysical Journal. 13: 226–230. Bibcode:1901ApJ....13..226P. doi:10.1086/140808. Retrieved 3 January 2025.
^ Dunér; Hartwig; Müller (June 1912). "Benennung von neu entdeckten veränderlichen Sternen". Astronomische Nachrichten. 191 (19): 341–358. doi:10.1002/asna.19121911902. Retrieved 3 January 2025.
^ Herwig, Falk; Austin, Sam M. (2004). "Nuclear Reaction Rates and Carbon Star Formation". The Astrophysical Journal. 613 (1): L73 – L76. arXiv:astro-ph/0408394. Bibcode:2004ApJ...613L..73H. doi:10.1086/424872. S2CID 119462309.