Gamma Geminorum
 Alhena is the γ star in the constellation of Gemini. |
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| Observation data Epoch J2000 Equinox J2000 |
|
|---|---|
| Constellation | Gemini |
| Right ascension | 06h 37m 42.7s |
| Declination | +16° 23′ 57″ |
| Apparent magnitude (V) | 1.93 |
| Characteristics | |
| Spectral type | A0 IV |
| U−B color index | 0.06 |
| B−V color index | 0.00 |
| Variable type | ? |
| Astrometry | |
| Radial velocity (Rv) | -12.1 km/s |
| Proper motion (μ) | RA: -2.04 mas/yr Dec.: -66.92 mas/yr |
| Parallax (π) | 31.12 ± 2.33 mas |
| Distance | 105 ± 8 ly (32 ± 2 pc) |
| Absolute magnitude (MV) | -0.61 |
| Details | |
| Mass | 2.81[1] M☉ |
| Radius | 4.4 R☉ |
| Luminosity | 160 L☉ |
| Temperature | 9,750 K |
| Rotational velocity (v sin i) | 32 km/s |
| Other designations | |
Gamma Geminorum (γ Gem, γ Geminorum) is the second brightest star in the constellation Gemini. It has the traditional names Alhena and Almeisan.
The term Alhena is derived from the Arabic الهنعه Al Han'ah, "the brand" (on the neck of the camel), whilst the alternate name Almeisan is from the Arabic المیسان Al Maisan, "the shining one." Al Hanʽah was the name of star association consisting this star, along with μ Gem (Tejat Posterior), ν Gem, η Gem (Tejat Prior) and ξ Gem (Alzirr). They also were associated in Al Nuḥātai, the dual form of Al Nuḥāt, "a Camel's Hump"[2]
In the catalogue of stars in the Calendarium of Al Achsasi Al Mouakket, this star was designated Nir al Henat, which was translated into Latin as Prima του al Henat, meaning the brightest of Al Henat.[3]
In Chinese, 井宿 (Jǐng Su), meaning Well (asterism), refers to an asterism consisting of γ Geminorum, μ Geminorum, ν Geminorum, ξ Geminorum, ε Geminorum, 36 Geminorum, ζ Geminorum and λ Geminorum.[4] Consequently, γ Geminorum itself is known as 井宿三 (Jǐng Su sān, English: the Third Star of Well.)[5]
[edit] Structure
Alhena is 105 light-years (32 pc) distant from Earth, and has an apparent magnitude of 1.93 (absolute magnitude −0.7) and belongs to the spectral class A0. It is a spectroscopic binary with a faint class-G companion.
[edit] Alhena as a name
Alhena was the name of a Dutch ship that rescued many people from an Italian cruise liner, the Principessa Mafalda, in October 1927.[6] In addition, the American attack cargo ship USS Alhena was named after the star.
[edit] References
- ^ Shaya, Ed J.; Olling, Rob P. (January 2011), "Very Wide Binaries and Other Comoving Stellar Companions: A Bayesian Analysis of the Hipparcos Catalogue", The Astrophysical Journal Supplement 192 (1): 2, Bibcode 2011ApJS..192....2S, doi:10.1088/0067-0049/192/1/2
- ^ Allen, R. H. (1963). Star Names: Their Lore and Meaning (Reprint ed.). New York: Dover Publications Inc. p. 234. ISBN 0486210790. http://penelope.uchicago.edu/Thayer/E/Gazetteer/Topics/astronomy/_Texts/secondary/ALLSTA/Gemini*.html. Retrieved 2010-12-12.
- ^ 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.
- ^ (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.
- ^ (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.
- ^ http://www.markos.it/quaderni/plata.htm Italian account of the Principessa Malfeda.
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