Epsilon Canis Majoris

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ε Canis Majoris
Template:Location mark
Location of ε Canis Majoris (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Canis Major
ε CMa A
Right ascension Template:RA[1]
Declination Template:DEC[1]
Apparent magnitude (V) 1.50[2]
ε CMa B
Right ascension Template:RA[3]
Declination Template:DEC[3]
Apparent magnitude (V) +7.5[4]
Characteristics
ε CMa A
Evolutionary stage Blue giant,[5][6] main sequence[7][8] or stellar merger product[8]
Spectral type B2 II[6] or B2 III-II[5]
U−B Template:Engvar −0.93[2]
B−V Template:Engvar −0.21[2]
Astrometry
ε CMa A
Radial velocity (Rv)+Script error: No such module "val".[9] km/s
Proper motion (μ) RA: +3.24 mas/yr[1]
Dec.: +1.33 mas/yr[1]
Parallax (π)8.05±0.14 mas[1]
DistanceTemplate:Rnd ± Template:Rnd ly
(Template:Rnd ± Template:Rnd pc)
Absolute magnitude (MV)Script error: No such module "val".[5]
ε CMa B
Radial velocity (Rv)+Script error: No such module "val".[3] km/s
Proper motion (μ) RA: +1.802 mas/yr[3]
Dec.: Script error: No such module "val". mas/yr[3]
Parallax (π)7.6159±0.0223 mas[3]
DistanceTemplate:Rnd ± Template:Rnd ly
(Template:Rnd ± Template:Rnd pc)
Position (relative to A)[4]
ComponentB
Epoch of observation2008
Angular distance7.90″
Position angle162°
Details
ε CMa A
MassScript error: No such module "val".[5] Template:Solar mass
RadiusScript error: No such module "val".[5] Template:Solar radius
LuminosityScript error: No such module "val".[5] Template:Solar luminosity
Script error: No such module "val".[10] Template:Solar luminosity
Surface gravity (log g)Script error: No such module "val".[5] cgs
TemperatureScript error: No such module "val".[10] K
Rotation5[8] days
Rotational velocity (v sin i)25[11] km/s
Age17.5Template:Snd19[7] Myr
ε CMa B
Mass1.54[3] Template:Solar mass
Radius1.54[3] Template:Solar radius
Luminosity6.13[3] Template:Solar luminosity
Surface gravity (log g)4.15[3] cgs
Temperature7,315[3] K
Metallicity [Fe/H]{{{metal_fe2}}} dex
Other designations
Template:Odlist[12]
Database references
ε CMa A
SIMBADdata
ε CMa B
SIMBADdata

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Epsilon Canis Majoris is a binary star system and the second-brightest star in the constellation of Canis Major. Its name is a Bayer designation that is Latinised from ε Canis Majoris, and abbreviated Epsilon CMa or ε CMa. This is the 22nd-brightest star in the night sky with an apparent magnitude of 1.50. About 4.7 million years ago, it was the brightest star in the night sky, with an apparent magnitude of −3.99.[13] Based upon parallax measurements obtained during the Hipparcos and the Gaia mission, it is about Script error: No such module "val". light-years distant.[1]

The two components are designated ε Canis Majoris A, officially named Adhara Template:IPAc-en – the traditional name of the system,[14][15] and B.[16]

Nomenclature

ε Canis Majoris (Latinised to Epsilon Canis Majoris) is the binary system's Bayer designation. The designations of the two components as ε Canis Majoris A and B derive from the convention used by the Washington Multiplicity Catalog (WMC) for multiple star systems, and adopted by the International Astronomical Union (IAU).[17]

ε Canis Majoris bore the traditional name Adhara (sometimes spelled Adara, Adard, Udara or Udra), derived from the Arabic word عذارى 'aðāra', "virgins".[18] In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN)[19] to catalogue and standardize proper names for stars. The WGSN decided to attribute proper names to individual stars rather than entire star systems.[20] It approved the name Adhara for the star ε Canis Majoris A on 21 August 2016 and it is now so included in the List of IAU-approved Star Names.[15]

In the 17th-century catalogue of stars in the Calendarium of Al Achsasi al Mouakket, this star was designated Aoul al Adzari (أول العذاري awwal al-adhara), which was translated into Latin as Prima Virginum, meaning First of the Virgins.[21] Along with δ Canis Majoris (Wezen), η Canis Majoris (Aludra) and ο2 Canis Majoris (Thanih al Adzari), these stars were Al ʽAdhārā (العذاري), 'the Virgins'.[18][22]

In Chinese, Script error: No such module "Lang". (Script error: No such module "Lang".), meaning Bow and Arrow,[23] refers to an asterism consisting of ε Canis Majoris, δ Canis Majoris, η Canis Majoris, κ Canis Majoris, ο Puppis, π Puppis, χ Puppis, c Puppis and k Puppis. Consequently, ε Canis Majoris itself is known as Script error: No such module "Lang". (Script error: No such module "Lang"., Template:Langx).[24]

Physical properties

ε Canis Majoris is a binary star.[25][26] The primary, ε Canis Majoris A, has an apparent magnitude of +1.5 and belongs to the spectral classification B2. Its color is blue or blueish-white, due to the surface temperature of Script error: No such module "val".. It emits a total radiation equal to 38,700 times that of the Sun. This star is the brightest source of extreme ultraviolet in the night sky.[27] It is the strongest source of photons capable of ionizing hydrogen atoms in interstellar gas near the Sun, and is very important in determining the ionization state of the Local Interstellar Cloud.[28] Its rotation period is estimated to be about 5 days.[8]

The exact evolutionary status of ε CMa A is uncertain. Spectroscopically it has been given the class B2 II,[6] with the luminosity class of II indicating that is a bright giant, more luminous than a typical giant (luminosity class III). However, it appear less luminous than the expected for this luminosity class, and is more likely of class B2 III-II.[5] Two studies suggest ε CMa is still in the late main sequence (TAMS), rather than being a giant.[7][8] One of these even suggested it could be the final product of a stellar merger.[8]

The +7.5-magnitude (the absolute magnitude amounts to +1.9) companion star, ε Canis Majoris B, is Script error: No such module "val". away with a position angle of 161° of the main star. Despite the relatively large angular distance the components can only be resolved in large telescopes, since the primary is approximately 250 times brighter than its companion.[4]

A few million years ago, ε Canis Majoris was much closer to the Sun than it is at present, causing it to be a much brighter star in the night sky. About 4.4 million years ago, Adhara was Script error: No such module "convert". from the Sun, and was the brightest star in the night sky with a magnitude of Script error: No such module "val"..Template:Efn No other star has attained this brightness since, nor will any other star attain this brightness for at least five million years.[13][5]

In culture

USS Adhara (AK-71) was a U.S. Navy Crater-class cargo ship named after the star.

ε Canis Majoris appears on the national flag of Brazil, symbolising the state of Tocantins.[29]

Notes

Template:Notelist

References

  1. ↑ a b c d e Script error: No such module "Citation/CS1".
  2. ↑ a b c Script error: No such module "Citation/CS1".
  3. ↑ a b c d e f g h i j Template:Cite DR3
  4. ↑ a b c Script error: No such module "Citation/CS1".
  5. ↑ a b c d e f g h i Script error: No such module "Citation/CS1".
  6. ↑ a b c Script error: No such module "Citation/CS1".
  7. ↑ a b c Script error: No such module "Citation/CS1".
  8. ↑ a b c d e f Script error: No such module "Citation/CS1".
  9. ↑ Script error: No such module "Citation/CS1".
  10. ↑ a b Script error: No such module "Citation/CS1".
  11. ↑ Script error: No such module "Citation/CS1".
  12. ↑ Template:Cite simbad
  13. ↑ a b Script error: No such module "Citation/CS1".
  14. ↑ Script error: No such module "citation/CS1".
  15. ↑ a b Script error: No such module "citation/CS1".
  16. ↑ Template:Cite simbad
  17. ↑ Script error: No such module "citation/CS1".
  18. ↑ a b Script error: No such module "citation/CS1".
  19. ↑ Script error: No such module "citation/CS1".
  20. ↑ Script error: No such module "citation/CS1".
  21. ↑ Script error: No such module "Citation/CS1".
  22. ↑ ε CMa as Aoul al Adzari or Prima Virginum (First of the Virgins), Omicron2 Canis Majoris as Thanih al Adzari or Secunda Virginum (Second of the Virgins) and Delta Canis Majoris as Thalath al Adzari or Tertia Virginum (Third of the Virgins). Eta Canis Majoris should be Rabah al Adzari or Quarta Virginum (Fourth of the Virgins) consistently, but it was given by the name Aludra, meaning Virgin (same meaning with Adhara or Al ʽAdhārā)
  23. ↑ 弧矢 (Hú Shǐ) is westernized into Koo She. R.H. Allen opined that Koo She refers to the asterism including Delta Velorum and Omega Carinae. AEEA opinion is, Delta Velorum is member of Script error: No such module "Lang". (Script error: No such module "Lang".), meaning Celestial Earth God's Temple asterism and Omega Carinae is not a 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 Template:In lang AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 7 月 17 日 Template:Webarchive.
  24. ↑ Template:In lang AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 7 月 17 日 Template:Webarchive
  25. ↑ Script error: No such module "Citation/CS1".
  26. ↑ Script error: No such module "citation/CS1".
  27. ↑ Script error: No such module "Citation/CS1".
  28. ↑ Script error: No such module "Citation/CS1".
  29. ↑ Script error: No such module "citation/CS1".

Template:Stars of Canis Major Template:Authority control Template:Sky

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