Mu Geminorum or μ Geminorum, formally named Tejat (/ˈtiːdʒət/),[13] 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.[1] The position of the star near the ecliptic means that it is subject to lunar occultations.[10]
Star in the constellation Gemini
μ Geminorum
Location of μ Geminorum (circled)
Observation data Epoch J2000.0Equinox J2000.0 (ICRS)
Mu Geminorum forms the primary or 'A' component of a double star system designated WDSJ06230+2231 along with UCAC2 39641417[14] (also designated WDSJ06230+2231BC), itself a binary pair.[15]
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. WDSJ06230+2231 is the double star's designation in the Washington Double Star Catalog. The designations of the double star's components as WDSJ06230+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).[16]
Mu Geminorum bore the traditional name of Tejat (or more precisely, Tejat Posterior), from an old southern Arabic word of unknown meaning, tiḥyāt.[17] 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).[15] In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN)[18] to catalogue and standardize proper names for stars. The WGSN decided to attribute proper names to individual stars rather than entire multiple systems.[19] It approved the name Tejat for the component WDSJ06230+2231A (i.e. Mu Geminorum) on February 1, 2017 and it is now so included in the List of IAU-approved Star Names.[13]
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.[20]
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.[21] Consequently, Mu Geminorum itself is known as 井宿一 (Jǐng Su yī, English: the First Star of Well).[22]
Properties
Visual band light curves for Mu Geminorum, adapted from Percy et al. (2001).[23] The 27 day periodicity is visible in the lower plot.
Mu Geminorum has an average apparent visual magnitude of about 2.9,[5][2] 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.[24] Seen from Earth, its brightness is reduced by 0.07 magnitudes by extinction from intervening gas and dust.[6]
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 M3III,[4] with a surface temperature of 3,773 K,[25] meaning it is brighter, yet cooler, than the Sun.[2][15] 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.[3]
Lebzelter, T.; Hron, J. (January 2008), "BRITE stars on the AGB", Communications in Asteroseismology, 152: 178–181, Bibcode:2008CoAst.152..178L, doi:10.1553/cia152s178.
Gutierrez-Moreno, Adelina; etal. (1966), "A System of photometric standards", Publications of the Department of Astronomy University of Chile, Publicaciones Universidad de Chile, Department de Astronomy, 1: 1–17, Bibcode:1966PDAUC...1....1G.
Famaey, B.; etal. (January 2005), "Local kinematics of K and M giants from CORAVEL/Hipparcos/Tycho-2 data. Revisiting the concept of superclusters", Astronomy and Astrophysics, 430 (1): 165–186, arXiv:astro-ph/0409579, Bibcode:2005A&A...430..165F, doi:10.1051/0004-6361:20041272, S2CID17804304.
Schiavon, Ricardo P. (July 2007), "Population Synthesis in the Blue. IV. Accurate Model Predictions for Lick Indices and UBV Colors in Single Stellar Populations", The Astrophysical Journal Supplement Series, 171 (1): 146–205, arXiv:astro-ph/0611464, Bibcode:2007ApJS..171..146S, doi:10.1086/511753, S2CID13946698.
Massarotti, Alessandro; etal. (January 2008), "Rotational and Radial Velocities for a Sample of 761 HIPPARCOS Giants and the Role of Binarity", The Astronomical Journal, 135 (1): 209–231, Bibcode:2008AJ....135..209M, doi:10.1088/0004-6256/135/1/209.
Mondal, Soumen; Chandrasekhar, T. (August 2005), "Angular Diameter Measurements of Evolved Variables by Lunar Occultations at 2.2 and 3.8 Microns", The Astronomical Journal, 130 (2): 842–852, arXiv:astro-ph/0504326, Bibcode:2005AJ....130..842M, doi:10.1086/430457.
Hessman, F. V.; Dhillon, V. S.; Winget, D. E.; Schreiber, M. R.; Horne, K.; Marsh, T. R.; Guenther, E.; Schwope, A.; Heber, U. (2010), On the naming convention used for multiple star systems and extrasolar planets, arXiv:1012.0707.
Kunitzsch, Paul; Smart, Tim (2006), A Dictionary of Modern star Names: A Short Guide to 254 Star Names and Their Derivations (2nd rev.ed.), Cambridge, Massachusetts: Sky Pub, ISBN978-1-931559-44-7.
White, Nathaniel M.; Feierman, Barry H. (September 1987), "A Catalog of Stellar Angular Diameters Measured by Lunar Occultation", Astronomical Journal, 94: 751, Bibcode:1987AJ.....94..751W, doi:10.1086/114513.
Mallik, Sushma V. (December 1999), "Lithium abundance and mass", Astronomy and Astrophysics, 352: 495–507, Bibcode:1999A&A...352..495M.
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