Delta Canis Majoris

d Canis Majoris

δ CMa, a yellow supergiant 1800 lightyears away in the Canis Major constellation
Observation data Epoch J2000      Equinox J2000
Constellation	Canis Major
Right ascension	07h 08m 23.5s
Declination	-26° 23′ 36″
Apparent magnitude (V)	1.83
Characteristics
Spectral type	F8 Ia
U−B color index	0.54
B−V color index	0.68
Variable type	Alpha Cygni
Astrometry
Radial velocity (Rv)	34 km/s
Proper motion (μ)	RA: -2.75 mas/yr Dec.: 3.33 mas/yr
Parallax (π)	1.82 ± 0.56 mas
Distance	approx. 1800 ly (approx. 500 pc)
Absolute magnitude (MV)	-6.87
Details
Mass	17 M☉
Radius	215 R☉
Luminosity	50,000 L☉
Temperature	6,200 K
Metallicity	?
Rotation	~28 km/s.
Age	1 × 107 years
Other designations
Wezen, Wesen, Alwazn, Al Wazor, 25 Canis Majoris, HR 2693, HD 54605, SAO 173047, FK5 273, CD−26°3916, CPD−26°1793, HIP 34444, GC 9443, CCDM 07084-2624

Delta Canis Majoris (δ CMa, δ Canis Majoris) is a star in the constellation Canis Major. It has the traditional name Wezen or Wesen. It is a yellow-white F-type supergiant with an apparent magnitude of +1.83.

Visibility

δ Canis Majoris is the third brightest star in the constellation after Sirius and Adhara, with an apparent magnitude of +1.83, and is a white or yellow-white in colour. Lying about 10 degrees south southeast of Sirius, it only rises to about 11 degrees above the horizon at the latitude of the United Kingdom.^[1] The open cluster NGC 2354 is located only 1.3 degrees east of Delta Canis Majoris.^[2] As with the rest of Canis Major, Wezen is most visible in winter skies in the northern hemisphere, and summer skies in the southern. It theoretically makes up the Great Dog's hind quarter.^[3]

History and naming

The traditional name, Wezen, is derived from the medieval Arabic وزن al-wazn, which means "weight" in modern Arabic. The name was for one of a pair of stars, the other being Hadar, which has now come to refer to Beta Centauri. It is unclear whether the pair of stars was originally Alpha and Beta Centauri or Alpha and Beta Columbae. In any case, the name was somehow applied to both Delta Canis Majoris and Beta Columbae.^[4] Richard Hinckley Allen muses that the name alludes to the difficulty the star has rising above the (northern hemisphere) horizon.^[3] Astronomer Jim Kaler has noted the aptness of the traditional name given the star's massive nature.^[5]

In Chinese, 弧矢 (Hú Shǐ), meaning Bow and Arrow,^[6] refers to an asterism consisting of δ Canis Majoris, η Canis Majoris, c Puppis, ZI 674, ο Puppis, κ Puppis, ε Canis Majoris, κ Canis Majoris and π Puppis.^[7] Consequently, δ Canis Majoris itself is known as 弧矢一 (Hú Shǐ yī, English: the First Star of Bow and Arrow.)^[8]

In the catalogue of stars in the Calendarium of Al Achsasi Al Mouakket, this star was designated Thalath al Adzari (تالت ألعذاري - taalit al-aðārii), which was translated into Latin as Tertia Virginum, meaning the third virgin.^[9] This star, along with ε CMa (Adhara), η CMa (Aludra) and ο² CMa (Thanih al Adzari), were Al ʽAdhārā (ألعذاري), the Virgins.^[10][11]

Properties

Wezen is a supergiant of class F8 with a radius around 215 times that of the Sun. Its surface temperature is around 5818 K,^[12] and it weighs around 17 solar masses. Its absolute magnitude is -6.87, and it lies around 1800 light years away. It is rotating at a speed of around 28 km/s, and hence may take a year to rotate fully. Only around 10 million years old, Wezen has stopped fusing hydrogen in its core. Its outer envelope is beginning to expand and cool, and in the next 100,000 years it will become a red supergiant as its core fuses heavier and heavier elements. Once it has a core of iron, it will collapse and explode as a supernova.^[5]

If Wezen were as close to Earth as Sirius is, it would be as bright as a half-full moon.^[13]

Modern legacy

Wezen appears on the flag of Brazil, symbolising the state of Roraima.^[14]

References

1. ^ Mobberly, Martin (2009). The Caldwell Objects and How to Observe Them. Springer. p. 136. ISBN 1441903259. http://books.google.com/?id=amPrWoOWgHcC&pg=PA136&dq=Wezen+Canis#v=onepage&q=Wezen%20Canis&f=false. Retrieved 28 May 2010. 
2. ^ http://www.angelfire.com/ky/astronomers/Canis.html
3. ^ ^{a b} Allen R H (1963) [1899]. Star Names: Their Lore and Meaning (rep. ed.). New York, NY: Dover Publications Inc.. p. 130. ISBN 0486210790. 
4. ^ Kunitzsch P, Smart T, (2006). A Dictionary of Modern star Names: A Short Guide to 254 Star Names and Their Derivations (2nd rev. ed.). Cambridge, MA: Sky Pub. p. 23. ISBN 9781931559447. 
5. ^ ^{a b} Kaler, James B.. "Wezen". Stars website. University of Illinois. http://stars.astro.illinois.edu/sow/wezen.html. Retrieved 28 May 2010. 
6. ^ 弧矢 (Hú Shǐ) is westernized into Koo She. R.H. Allen had opinion that Koo She refers to the asterism including δ Velorum and ω Velorum. AEEA opinion is, δ Velorum is member of 天社 (Tiān Shè), meaning Celestial Earth God's Temple asterism and ω Velorum is not member of any asterisms. 天社 (Tiān Shè) is westernized into Tseen She and R.H.Allen used the term Tseen She for Chinese name of η Carinae. See Richard Hinckley Allen: Star Names — Their Lore and Meaning: Argo Navis and (Chinese) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 7 月 17 日.
7. ^ (Chinese) 中國星座神話, written by 陳久金. Published by 台灣書房出版有限公司, 2005, ISBN 9789867332257.
8. ^ (Chinese) 香港太空館 - 研究資源 - 亮星中英對照表, Hong Kong Space Museum. Accessed on line November 23, 2010.
9. ^ Knobel, E. B. (June 1895). "Al Achsasi Al Mouakket, on a catalogue of stars in the Calendarium of Mohammad Al Achsasi Al Mouakket". Monthly Notices of the Royal Astronomical Society 55: 429. Bibcode 1895MNRAS..55..429K. 
10. ^ Allen, R. H. (1963). Star Names: Their Lore and Meaning (Reprint ed.). New York: Dover Publications Inc. p. 130. ISBN 0486210790. http://penelope.uchicago.edu/Thayer/E/Gazetteer/Topics/astronomy/_Texts/secondary/ALLSTA/Canis_Major*.html. Retrieved 2010-12-12. 
11. ^ ε CMa as Aoul al Adzari or Prima Virginum (the first virgin), ο² CMa as Thanih al Adzari or Secunda Virginum (the second virgin) and δ CMa as Thalath al Adzari or Tertia Virginum (the third virgin). η CMa should be Rabah al Adzari or Quarta Virginum (the fourth virgin) consistently, but it was given by the name Aludra, meaning the virgin (same meaning with Adhara (ε CMa) or Al ʽAdhārā)
12. ^ Davis J, Booth AJ, Ireland MJ, Jacob AP, North JR, Owens SM, Robertson JG, Tango WJ, Tuthill PG, J.; Booth, A. J.; Ireland, M. J.; Jacob, A. P.; North, J. R.; Owens, S. M.; Robertson, J. G.; Tango, W. J. et al. (2007). "The Emergent Flux and Effective Temperature of Delta Canis Majoris". Publications of the Astronomical Society of Australia 24 (3): 151. arXiv:0709.3873. Bibcode 2007PASA...24..151D. doi:10.1071/AS07017. 
13. ^ Ridpath, Ian; Tirion, Will (2003). The Monthly Sky Guide. Cambridge University Press. p. 16. ISBN 0521533066. http://books.google.com/?id=UFQIutJ8GSsC&pg=PA15&dq=%22Delta+Canis+Majoris%22#v=onepage&q=%22Delta%20Canis%20Majoris%22&f=false. 
14. ^ "Astronomy of the Brazilian Flag". FOTW Flags Of The World website. http://www.fotw.net/flags/br_astro.html.