Gamma Geminorum
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 Alhena is the γ star in the constellation of Gemini. |
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| Observation data Epoch J2000 |
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|---|---|
| Constellation | Gemini |
| Right ascension | 06h 37m 42.7s |
| Declination | +16° 23′ 57″ |
| Apparent magnitude (V) | 1.93 |
| Spectral 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 |
| Physical Characteristics | |
| 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 a star in the constellation Gemini. It also has traditional names Alhena and Almeisan. It is known as 井宿三 (the Third Star of the Well) in Chinese.
Alhena is 105 light years 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.
The name Alhena is from the Arabic Al Han'ah, "the brand" (on the neck of the camel), whilst the alternate name Almeisan is from the Arabic Al Maisan, "the shining one."
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