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| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) |
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|---|---|
| Constellation | Gemini |
| Right ascension | 06h 22m 57.627s[1] |
| Declination | +22° 30′ 48.91″[1] |
| Apparent magnitude (V) | +2.75 to +3.02[2] |
| Characteristics | |
| Spectral type | M3.0IIIab[2] |
| U−B color index | 1.85[3] |
| B−V color index | 1.64[3] |
| Variable type | LB[2] |
| Astrometry | |
| Parallax (π) | 14.07 ± 0.93[1] mas |
| Distance | 230 ± 20 ly (71 ± 5 pc) |
| Other designations | |
Mu Geminorum (μ Gem, μ Geminorum) is a star in the constellation Gemini, approximately 230 light years away from Earth.[1] It has the traditional name Tejat Posterior, which means back foot, because it is the foot of Castor, one of the Gemini twins. The names Calx (Latin, meaning heel), Nuhatai (from Arabic Al Nuḥātai, the dual form of Al Nuḥāt, "a Camel's Hump". This is the name of star association consisting this star, along with γ Gem - Alhena, ν Gem, η Gem - Tejat Prior and ξ Gem - Alzirr) and Pish Pai (from the Persian Pīshpāy, پیشپای, meaning foreleg) have also been applied to this star.[4][5][6]
In Chinese, 井宿 (Jǐng Su), meaning Well (asterism), refers to an asterism consisting of μ Geminorum, γ Geminorum, ν Geminorum, ξ Geminorum, ε Geminorum, 36 Geminorum, ζ Geminorum and λ Geminorum.[7] Consequently, μ Geminorum itself is known as 井宿一 (Jǐng Su yī, English: the First Star of Well.)[8]
Mu Geminorum is an irregular variable of type LB. Its brightness varies between magnitude +2.75 and +3.02 over a 72 day period, with a 2,000 day period of long term variation. It is a red giant of the spectral class M3, with a surface temperature of 3,650 kelvins, meaning it is brighter, yet cooler than our Sun.[2][4]
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