Epoch J2000.0 Equinox J2000.0 (ICRS)
|Right ascension||06h 22m 57.62686s|
|Declination||+22° 30′ 48.8979″|
|Apparent magnitude (V)||2.857|
|Evolutionary stage||asymptotic giant branch|
|Spectral type||M3 III|
|U−B color index||+1.924|
|B−V color index||+1.643|
|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|
|Distance||230 ± 10 ly |
(71 ± 4 pc)
|Absolute magnitude (MV)||−1.42|
|Surface gravity (log g)||0.82 cgs|
|Metallicity [Fe/H]||−0.03 dex|
|Rotational velocity (v sin i)||8.4 km/s|
Mu Geminorum (μ Geminorum, abbreviated Mu Gem, μ Gem), formally named Tejat //, 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.
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).
Mu Geminorum has an average apparent visual magnitude of 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.
- van Leeuwen, F. (November 2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, arXiv:0708.1752, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357.
- Gutierrez-Moreno, Adelina; et al. (1966), A System of photometric standards, 1, Publicaciones Universidad de Chile, Department de Astronomy, pp. 1–17, Bibcode:1966PDAUC...1....1G.
- 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.
- Morgan, W. W.; Keenan, P. C. (1973), "Spectral Classification", Annual Review of Astronomy and Astrophysics, 11: 29, Bibcode:1973ARA&A..11...29M, doi:10.1146/annurev.aa.11.090173.000333.
- mu Gem[permanent dead link], entry in the Combined General Catalog of Variable Stars (GCVS4.2)[permanent dead link], N. N. Samus, O. V. Durlevich, et al., database identifier II/250 at the Centre de Données astronomiques de Strasbourg.
- Famaey, B.; et al. (January 2005), "Local kinematics of K and M giants from CORAVEL/Hipparcos/Tycho-2 data. Revisiting the concept of superclusters" (Submitted manuscript), Astronomy and Astrophysics, 430 (1): 165–186, arXiv:astro-ph/0409579, Bibcode:2005A&A...430..165F, doi:10.1051/0004-6361:20041272.
- 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.
- Tsuji, Takashi (May 2007). "Isotopic abundances of Carbon and Oxygen in Oxygen-rich giant stars". In Kupka, F.; Roxburgh, I.; Chan, K. (eds.). Convection in Astrophysics, Proceedings of IAU Symposium #239 held 21-25 August, 2006 in Prague, Czech Republic. Proceedings of the International Astronomical Union. 2. pp. 307–310. arXiv:astro-ph/0610180. Bibcode:2007IAUS..239..307T. doi:10.1017/S1743921307000622.
- Massarotti, Alessandro; et al. (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.
- Wu, Yue; Singh, H. P; Prugniel, P; Gupta, R; Koleva, M (2010). "Coudé-feed stellar spectral library – atmospheric parameters". Astronomy & Astrophysics. 525: A71. arXiv:1009.1491. Bibcode:2011A&A...525A..71W. doi:10.1051/0004-6361/201015014.
- "mu. Gem". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved October 12, 2007.
- "Naming Stars". IAU.org. Retrieved 16 December 2017.
- "UCAC2 39641417 -- Double or multiple star", SIMBAD, Centre de Données astronomiques de Strasbourg, retrieved 2018-07-28.
- "Tejat". Jim Kaler's STARS. Retrieved 2017-03-31.
- 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 [astro-ph.SR].
- 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. ISBN 978-1-931559-44-7.
- "International Astronomical Union | IAU". www.iau.org. Retrieved 2017-04-01.
- "WG Triennial Report (2015-2018) - Star Names" (PDF). p. 5. Retrieved 2018-07-14.
- Allen, Richard Hinckley (1899), Star-names and Their Meanings, G. E. Stechert, p. 236
- (in Chinese) 中國星座神話, written by 陳久金. Published by 台灣書房出版有限公司, 2005, ISBN 978-986-7332-25-7.
- (in Chinese) 香港太空館 - 研究資源 - 亮星中英對照表 Archived 2010-08-19 at the Wayback Machine, Hong Kong Space Museum. Accessed on line November 23, 2010.
- 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.