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Alhena is the γ star in the constellation of Gemini. |
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| Observation data Epoch J2000 Equinox J2000 |
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|---|---|
| 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 | 2.8 M☉ |
| Radius | 4.4 R☉ |
| Luminosity | 160 L☉ |
| Temperature | 9,750 K |
| Metallicity | ? |
| Rotation | 32 km/s. |
| Age | ? years |
| 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"[1]
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.[2]
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.[3] Consequently, γ Geminorum itself is known as 井宿三 (Jǐng Su sān, English: the Third Star of Well.)[4]
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.
Alhena was the name of a Dutch ship that rescued many people from an Italian cruise liner, the Principessa Mafalda, in October 1927.[5] In addition, the American attack cargo ship USS Alhena was named after the star.
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