Eta Canis Majoris

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Template:Short description

η Canis Majoris
Template:Location mark
Location of η Canis Majoris (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Canis Major
Right ascension Template:RA[1]
Declination Template:DEC[1]
Apparent magnitude (V) 2.38Template:Snd2.48[2]
Characteristics
Evolutionary stage Blue supergiant, likely a post-red supergiant[3]
Spectral type B5 Ia[4]
U−B Template:Engvar −0.708[5]
B−V Template:Engvar −0.087[5]
Variable type α Cyg[2]
Astrometry
Radial velocity (Rv)41.1[6] km/s
Proper motion (μ) RA: −4.14 mas/yr[1]
Dec.: 5.81 mas/yr[1]
Parallax (π)1.64±0.40 mas[1]
Distanceapprox. Template:Rnd ly
(approx. Template:Rnd pc)
Absolute magnitude (MV)−7.0[7]
Details
Mass5.5 or 9.5[3] Template:Solar mass
Radius54[8] Template:Solar radius
LuminosityScript error: No such module "val".[3] Template:Solar luminosity
Surface gravity (log g)Script error: No such module "val".[8] cgs
TemperatureScript error: No such module "val".[3] K
Rotational velocity (v sin i)Script error: No such module "val".[3] km/s
Age8.3[9] Myr
Metallicity [Fe/H]{{{metal_fe2}}} dex
Other designations
Template:Odlist
Database references
SIMBADdata

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Eta Canis Majoris is a blue supergiant star in the constellation of Canis Major. It has the proper name Aludra, pronounced Template:IPAc-en;[10] Eta Canis Majoris is its Bayer designation. This star has an apparent visual magnitude that varies between 2.38 and 2.48, which makes it the fifth-brightest in the constellation. Parallax measurements from the Hipparcos mission estimate a large distance of 2,000 light-years. It is drifting further away from the Sun with a line of sight velocity of 41 km/s.[6]

Nomenclature

η Canis Majoris, Latinised to Eta Canis Majoris, is the star's Bayer designation, abbreviated Eta CMa or η CMa.

The traditional name Aludra originates from the Arabic: العذراء al-adhraa, 'the virgin'. This star, along with Epsilon Canis Majoris (Adhara), Delta Canis Majoris (Wezen) and Omicron2 Canis Majoris (Thanih al Adzari), were Al 'Adhārā (العذاري), 'the Virgins'.[11] In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN)[12] to catalog and standardize proper names for stars. The WGSN's first bulletin of July 2016[13] included a table of the first two batches of names approved by the WGSN; which included Aludra for this star.

In Chinese, Script error: No such module "Lang". (Script error: No such module "Lang".), meaning Bow and Arrow,[14] refers to an asterism consisting of Eta Canis Majoris, Delta Canis Majoris, HD 63032, HD 65456, Omicron Puppis, k Puppis, Epsilon Canis Majoris, Kappa Canis Majoris and Pi Puppis. Consequently, Eta Canis Majoris itself is known as Script error: No such module "Lang". (Script error: No such module "Lang"., Template:Langx).[15]

Properties

File:EtaCMaLightCurve.png
A light curve for Eta Canis Majoris, plotted from Hipparcos data[16]

Eta Canis Majoris is a blue supergiant star with a spectral type of B5Ia.[3] It has been the standard for this spectral class in the Morgan–Keenan system, and since 1943, the spectrum of this star has served as one of the stable anchor points by which other stars are classified.[17][18]

This is likely a post-red supergiant, a star which left its red supergiant phase and is near the end of its life. As a consequence, Aludra has lost significant part of its mass. It formed with a mass of Template:Solar mass and now has either Template:Solar mass, depending on the estimate.[3] The present day mass loss rate is estimated at Script error: No such module "val".·yr−1, or one solar mass every 8.3 million years.[8]

Aludra shines brightly in the skies in spite of a large distance from Earth due to being intrinsically many times brighter than the Sun. It has a luminosity over 100,000 times and a radius around 54 times that of the Sun. The star has only existed for a fraction of the time the Sun has, less than 10 million years, yet is already in the final stages of its life.[8][3]

The star is classified as an Alpha Cygni-type variable star and its brightness varies from magnitude +2.38 to +2.48 over a period of 4.7 days.[2][19]

Namesakes

Both USS Aludra (AF-55), an Alstede-class stores ship, and USS Aludra (AK-72), a Crater-class cargo ship, were U.S. Navy vessels named after the star.

References

  1. ↑ a b c d 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 Script error: No such module "Citation/CS1".
  4. ↑ Script error: No such module "Citation/CS1".
  5. ↑ a b Script error: No such module "Citation/CS1".
  6. ↑ a b Script error: No such module "Citation/CS1".
  7. ↑ Script error: No such module "Citation/CS1".
  8. ↑ a b c d Script error: No such module "Citation/CS1".
  9. ↑ Script error: No such module "Citation/CS1".
  10. ↑ Script error: No such module "citation/CS1".
  11. ↑ Script error: No such module "citation/CS1".
  12. ↑ Script error: No such module "citation/CS1".
  13. ↑ Script error: No such module "citation/CS1".
  14. ↑ 弧矢 (Hú Shǐ) is westernized into Koo She. R.H. Allen had opinion 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 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 Eta 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.
  15. ↑ 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
  16. ↑ Script error: No such module "citation/CS1".
  17. ↑ Script error: No such module "Citation/CS1".
  18. ↑ Script error: No such module "citation/CS1".
  19. ↑ Script error: No such module "citation/CS1".

Template:Stars of Canis Major

Template:Authority control

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