Eta Canis Majoris
 Eta Canis Majoris, a blue Supergiant in Canis Major |
|
| Observation data Epoch J2000 Equinox J2000 |
|
|---|---|
| Constellation | Canis Major |
| Right ascension | 07h 24m 05.70228s[1] |
| Declination | –29° 18′ 11.1798″[1] |
| Apparent magnitude (V) | 2.450[2] |
| Characteristics | |
| Spectral type | B5 Ia[3] |
| U−B color index | −0.708[2] |
| B−V color index | −0.087[2] |
| Variable type | α Cyg[4] |
| Astrometry | |
| Radial velocity (Rv) | 41.1[5] km/s |
| Proper motion (μ) | RA: −4.14[1] mas/yr Dec.: 5.81[1] mas/yr |
| Parallax (π) | 1.64 ± 0.40[1] mas |
| Distance | approx. 2,000 ly (approx. 600 pc) |
| Absolute magnitude (MV) | -7.0[6] |
| Details | |
| Mass | 19.19 ± 1.15[7] M☉ |
| Radius | 56.3[6] R☉ |
| Luminosity | 105,442[7] L☉ |
| Temperature | 15,000[3] K |
| Rotational velocity (v sin i) | 50[8] km/s |
| Other designations | |
| Database references | |
| SIMBAD | data |
Eta Canis Majoris (η CMa, η Canis Majoris) is a star in the constellation Canis Major. It has the traditional name Aludra. Since 1943, the spectrum of this star has served as one of the stable anchor points by which other stars are classified.[9]
The name Aludra originates from the Arabic: عذرا al-‘aðrā "the virgin". This star, along with ε CMa (Adhara), δ CMa (Wezen) and ο2 CMa (Thanih al Adzari), were Al ʽAdhārā (ألعذاري), the Virgins.[10]
In Chinese, 弧矢 (Hú Shǐ), meaning Bow and Arrow,[11] refers to an asterism consisting of η Canis Majoris, δ Canis Majoris, HD 63032, HD 65456, ο Puppis, k Puppis, ε Canis Majoris, κ Canis Majoris and π Puppis. Consequently, η Canis Majoris itself is known as 弧矢二 (Hú Shǐ èr, English: the Second Star of Bow and Arrow.)[12]
Properties
Aludra shines brightly in the skies in spite of a large distance from Earth due to being intrinsically many times brighter (absolute magnitude) than the Sun. A blue-white supergiant of spectral type B5Ia, Aludra has a luminosity 176,000 times and a diameter around 80 times that of the Sun.[13] Hohle and colleagues, using the parallax, extinction and analysis of spectrum, came up with a mass 19.19 times that and luminosity 105,442 times that of the Sun.[7] It has only been around a fraction of the time our Sun has, yet is already in the last stages of its life. It is still expanding and may become a red supergiant, or perhaps has already passed that phase, but in either case it will become a supernova within the next few million years.
Aludra 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.[4][14]
Namesakes
Both USS Aludra (AF-55) and USS Aludra (AK-72), a Crater class cargo ship, were United States Navy vessels named after the star.
References
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- ↑ 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.
- ↑ (Chinese) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 7 月 17 日
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