Location of ε Geminorum (circled) | |
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Gemini |
| Right ascension | 06 43 55.927 |
| Declination | +25° 07′ 52.06″ |
| Apparent magnitude (V) | +3.06 |
| Characteristics | |
| Spectral type | G8 Ib |
| U−B color index | +1.46 |
| B−V color index | +1.40 |
| Astrometry | |
| Radial velocity (Rv) | +8.09±0.14 km/s |
| Proper motion (μ) | RA: −4.835 mas/yr Dec.: −11.78 mas/yr |
| Parallax (π) | 3.748 ± 0.184 mas |
| Distance | 861+52 −39 ly (264+16 −12 pc) |
| Absolute magnitude (MV) | −4.33±0.10 |
| Details | |
| Mass | 5.29±0.04 – 8.2±0.82 M☉ |
| Radius | 130.2+5.5 −6.0 R☉ |
| Luminosity | 6,980 L☉ |
| Surface gravity (log g) | 0.76–1.38 cgs |
| Temperature | 4,591±11 K |
| Metallicity | 0.15±0.07 dex |
| Rotational velocity (v sin i) | 9.08 km/s |
| Age | 100 Myr |
| Other designations | |
| Epsilon Gem, ε Gem, 27 Geminorum, FK5 254, HD 48329, HIP 32246, HR 2473, SAO 78682 | |
| Database references | |
| SIMBAD | data |
Epsilon Geminorum or ε Geminorum, formally named Mebsuta /mɛbˈsuːtə/, is a star in the constellation of Gemini, on the outstretched right 'leg' of the twin Castor. The apparent visual magnitude of +3.06 makes it one of the brighter stars in this constellation. The distance to this star is determined at 860 light-years (260 parsecs).
Nomenclature
ε Geminorum (Latinised to Epsilon Geminorum) is the star's Bayer designation. It bore the traditional names Mebsuta, Melboula or Melucta. Mebsuta has its roots in an ancient Arabian view where it and the star Mekbuda (Zeta Geminorum) were the paws of a huge lion extending over many present-day constellations. Mebsuta ('Mabsūṭah' مبسوطة) comes from a phrase referring to the outstretched paw. In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN) to catalog and standardize proper names for stars. The WGSN's first bulletin of July 2016 included a table of the first two batches of names approved by the WGSN; which included Mebsuta for this star.
In Chinese, 井宿 (Jǐng Su), meaning Well (asterism), refers to an asterism consisting of ε Geminorum, μ Geminorum, ν Geminorum, γ Geminorum, ξ Geminorum, 36 Geminorum, ζ Geminorum and λ Geminorum. Consequently, ε Geminorum itself is known as 井宿五 (Jǐng Su wǔ, English: the Fifth Star of Well.)
Properties
At Epsilon Geminorum's distance, extinction from interstellar dust is causing a magnitude reduction of 0.27. The spectrum of this star matches a stellar classification of G8 Ib, where the luminosity class of Ib indicates this is a lower luminosity supergiant star. Alternatively, it may be a star that has passed through the asymptotic giant branch stage and possesses a detached shell of dust. It has 5.3 times the mass of the Sun and it is estimated to be 100 million years old. Since 1943, the spectrum of this star has served as one of the stable anchor points by which other stars are classified.
The radius of Epsilon Geminorum has been directly measured using interferometry with the Navy Precision Optical Interferometer, which yields a result of 130 times the radius of the Sun. It is radiating around 7,000 times the luminosity of the Sun from its outer atmosphere at an effective temperature of 4,591 K. It is this temperature that gives it the yellow-hued glow of a G-type star. A surface magnetic field with a strength of −0.14±0.19 G has been detected on this star. This topologically complex field is most likely generated by a dynamo formed from the deep convection zone in the star's outer envelope.
Occultations
Epsilon Geminorum lies near the ecliptic, so it can be occulted by the Moon or a planet. Such an occultation took place on April 8, 1976 by Mars, which allowed the oblateness of the planet's outer atmosphere to be measured. Epsilon Geminorum was occulted by Mercury on June 10, 1940, and on September 3, 2015 it was occulted by the asteroid 112 Iphigenia.
In culture
USS Melucta (AK-131) was a United States Navy Crater class cargo ship named after the star.
References
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- ^ Mallik, Sushma V. (December 1999), "Lithium abundance and mass", Astronomy and Astrophysics, 352: 495–507, Bibcode:1999A&A...352..495M
- ^ Nordgren, Tyler E.; et al. (December 1999), "Stellar Angular Diameters of Late-Type Giants and Supergiants Measured with the Navy Prototype Optical Interferometer", The Astronomical Journal, 118 (6): 3032–3038, Bibcode:1999AJ....118.3032N, doi:10.1086/301114
- ^ Johnson, H. L.; et al. (1966), "UBVRIJKL photometry of the bright stars", Communications of the Lunar and Planetary Laboratory, 4 (99): 99, Bibcode:1966CoLPL...4...99J
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- ^ Bailer-Jones, C. A. L.; Rybizki, J.; Fouesneau, M.; Demleitner, M.; Andrae, R. (2021-03-01), "Estimating distances from parallaxes. V: Geometric and photogeometric distances to 1.47 billion stars in Gaia Early Data Release 3", The Astronomical Journal, 161 (3): 147, arXiv:2012.05220, Bibcode:2021AJ....161..147B, doi:10.3847/1538-3881/abd806, ISSN 0004-6256 Data about this star can be seen here.
- ^ Neuhäuser, R; Torres, G; Mugrauer, M; Neuhäuser, D L; Chapman, J; Luge, D; Cosci, M (October 2022). "Colour evolution of Betelgeuse and Antares over two millennia, derived from historical records, as a new constraint on mass and age". Monthly Notices of the Royal Astronomical Society. 516 (1): 693–719. arXiv:2207.04702. Bibcode:2022MNRAS.516..693N. doi:10.1093/mnras/stac1969. hdl:10278/5003332. ISSN 0035-8711.
- ^ Baines, Ellyn K.; Armstrong, J. Thomas; Schmitt, Henrique R.; Zavala, R. T.; Benson, James A.; Hutter, Donald J.; Tycner, Christopher; Belle, Gerard T. van (2017-12-21), "Fundamental Parameters of 87 Stars from the Navy Precision Optical Interferometer", The Astronomical Journal, 155 (1): 30, arXiv:1712.08109, Bibcode:2018AJ....155...30B, doi:10.3847/1538-3881/aa9d8b, ISSN 0004-6256
- ^ Rosas-Portilla, F.; Schröder, K.-P.; Jack, D. (2022-04-26), "On the physical nature of the Wilson-Bappu effect: revising the gravity and temperature dependence", Monthly Notices of the Royal Astronomical Society, 513 (1): 906–924, arXiv:2203.16593, doi:10.1093/mnras/stac929, ISSN 0035-8711
- Wu, Yue; et al. (January 2011), "Coudé-feed stellar spectral library - atmospheric parameters", Astronomy and Astrophysics, 525: A71, arXiv:1009.1491, Bibcode:2011A&A...525A..71W, doi:10.1051/0004-6361/201015014, S2CID 53480665
- Davis, George A. (1944), "The pronunciations, derivations, and meanings of a selected list of star names", Popular Astronomy, 52: 8–30, Bibcode:1944PA.....52....8D
- IAU Catalog of Star Names, retrieved 28 July 2016
- Allen, Richard Hinckley (1899), Star-names and their meanings, G. E. Stechert, p. 231 See also page 97.
- Allen, Richard Hinckley (1899), Star-names and their meanings, G. E. Stechert, p. 235
- "IAU Working Group on Star Names (WGSN)". Retrieved 22 May 2016.
- "Bulletin of the IAU Working Group on Star Names, No. 1" (PDF). Retrieved 28 July 2016.
- (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 January 30, 2011, at the Wayback Machine, Hong Kong Space Museum. Accessed on line November 23, 2010.
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- "The Colour of Stars", Australia Telescope, Outreach and Education, Commonwealth Scientific and Industrial Research Organisation, December 21, 2004, archived from the original on 2012-03-18, retrieved 2012-01-16
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- French, R. G.; Taylor, G. E. (March 1981), "Occultation of Epsilon Geminorum by Mars. IV - Oblateness of the Martian upper atmosphere", Icarus, 45 (3): 577–585, Bibcode:1981Icar...45..577F, doi:10.1016/0019-1035(81)90023-3
- Können, G. P.; Van Maanen, J. (1981), "Planetary occultations of bright stars", Journal of the British Astronomical Association, 91: 148–157, Bibcode:1981JBAA...91..148K
- Steve's Asteroid Occultations, archived from the original on 2015-09-23, retrieved 2015-03-20
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