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Mu Geminorum

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(Redirected from Tejat Posterior) Star in the constellation Gemini
μ Geminorum
Location of μ Geminorum (circled)
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Gemini
Right ascension 06 22 57.62686
Declination +22° 30′ 48.8979″
Apparent magnitude (V) 2.75 - 3.02
Characteristics
Evolutionary stage asymptotic giant branch
Spectral type M3 III
U−B color index +1.924
B−V color index +1.643
Variable type LB
Astrometry
Radial velocity (Rv)+54.38±0.24 km/s
Proper motion (μ) RA: +56.39 mas/yr
Dec.: –110.03 mas/yr
Parallax (π)14.08 ± 0.71 mas
Distance230 ± 10 ly
(71 ± 4 pc)
Absolute magnitude (MV)−1.42
Details
Mass1.9±0.5 M☉
Radius107.7 R☉
Luminosity1,692 L☉
Surface gravity (log g)0.82±0.09 cgs
Temperature3,643 K
Metallicity −0.03±0.03 dex
Rotational velocity (v sin i)8.4 km/s
Other designations
Tejat, Mu Gem, μ Gem, 13 Geminorum, BD+22°1304, FK5 241, HD 44478, HIP 30343, HR 2286, SAO 78297, ADS 4990A, CCDM J06230+2230A, WDS J06230+2231A
Database references
SIMBADdata

Mu Geminorum or μ Geminorum, formally named Tejat (/ˈtiːdʒət/), is a single star in the northern constellation of Gemini. From parallax measurements obtained during the Hipparcos mission, it is roughly 230 light-years (71 parsecs) distant from the Sun. The position of the star near the ecliptic means that it is subject to lunar occultations.

Mu Geminorum forms the primary or 'A' component of a double star system designated WDS J06230+2231 along with UCAC2 39641417 (also designated WDS J06230+2231BC), itself a binary pair.

Nomenclature

μ Gem is the star on the left, surrounded by the S249 nebula. The bright star on the right, near the IC 443 supernova remnant, is η Gem.

μ Geminorum (Latinised to Mu Geminorum) is the star's Bayer designation. WDS J06230+2231 is the double star's designation in the Washington Double Star Catalog. The designations of the double star's components as WDS J06230+2231A and BC derive from the convention used by the Washington Multiplicity Catalog (WMC) for multiple star systems, and adopted by the International Astronomical Union (IAU).

Mu Geminorum bore the traditional name of Tejat (or more precisely, Tejat Posterior), from an old southern Arabic word of unknown meaning, tiḥyāt. The name Tejat Posterior was formerly applied to an asterism consisting of this star, along with Gamma Geminorum (Alhena), Nu Geminorum, Eta Geminorum (Propus), and Xi Geminorum (Alzirr). In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN) to catalogue and standardize proper names for stars. The WGSN decided to attribute proper names to individual stars rather than entire multiple systems. It approved the name Tejat for the component WDS J06230+2231A (i.e. Mu Geminorum) on February 1, 2017 and it is now so included in the List of IAU-approved Star Names.

The names Calx (Latin, meaning 'heel'), Pish Pai (from the Persian پیش‌پای ('pīshpāy', meaning 'foreleg'), and Nuhatai (from Arabic 'Al Nuḥātai', the dual form of 'Al Nuḥāt', 'a Camel's Hump') have also been applied to Mu Geminorum.

In Chinese, 井宿 (Jǐng Su), meaning Well (asterism), refers to an asterism consisting of Mu Geminorum, Gamma Geminorum, Nu Geminorum, Xi Geminorum, Epsilon Geminorum, 36 Geminorum, Zeta Geminorum and Lambda Geminorum. Consequently, Mu Geminorum itself is known as 井宿一 (Jǐng Su yī, English: the First Star of Well).

Properties

Visual band light curves for Mu Geminorum, adapted from Percy et al. (2001). The 27 day periodicity is visible in the lower plot.

Mu Geminorum has an average apparent visual magnitude of about 2.9, which makes it the fourth-brightest member of Gemini. It is 0.8 degrees south of the ecliptic, so it is subject to occultations by the Moon and, rarely, by planets. Seen from Earth, its brightness is reduced by 0.07 magnitudes by extinction from intervening gas and dust.

It is a slow irregular variable of type LB. Its brightness varies between magnitude +2.75 and +3.02 over a 72-day period, along with a 2,000-day period of long term variation. It is a red giant at a stellar classification of M3 III, with a surface temperature of 3,773 K, meaning it is brighter, yet cooler, than the Sun. The star is currently on the asymptotic giant branch and is generating energy through the nuclear fusion of hydrogen and helium along concentric shells surrounding an inert core of carbon and oxygen.

Notes

References

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