Upsilon2 Eridani (υ² Eridani, abbreviated Upsilon2 Eri, υ2 Eri), officially named Theemin /ˈθiːmən/,[10][11] is a star in the constellation of Eridanus. It is visible to the naked eye with an apparent visual magnitude of 3.8.[2] Based upon parallax measurements obtained during the Hipparcos mission,[1] it is approximately 66 parsecs (214 light-years) from the Sun.
  | |
| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
|---|---|
| Constellation | Eridanus |
| Right ascension | 04h 35m 33.03834s[1] |
| Declination | −30° 33′ 44.4297″[1] |
| Apparent magnitude (V) | 3.804[2] |
| Characteristics | |
| Spectral type | G8+ III[3] |
| U−B color index | +0.740[2] |
| B−V color index | +0.968[2] |
| Astrometry | |
| Radial velocity (Rv) | −4.0±0.9[4] km/s |
| Proper motion (μ) | RA: −49.27[1] mas/yr Dec.: −12.72[1] mas/yr |
| Parallax (π) | 15.25 ± 0.19 mas[1] |
| Distance | 214 ± 3 ly (65.6 ± 0.8 pc) |
| Absolute magnitude (MV) | −0.27[5] |
| Details | |
| Radius | 16[6] R☉ |
| Luminosity | 138[7] L☉ |
| Surface gravity (log g) | 2.77±0.07[8] cgs |
| Temperature | 5,074±30[8] K |
| Metallicity [Fe/H] | 0.04±0.03[8] dex |
| Other designations | |
| Database references | |
| SIMBAD | data |
It is an evolved red clump[12] giant star with a stellar classification of G8+ III.[3] The measured angular diameter is 2.21 mas.[13] At the star's distance, this yields a physical size of around 16 times the radius of the Sun.[6] It radiates 138[7] times the solar luminosity from its outer atmosphere at an effective temperature of 5074 K.[8]
Nomenclature
editυ2 Eridani (Latinised to Upsilon2 Eridani) is the star's Bayer designation.
It bore the traditional name Theemin (also written as Theemim and Beemin).[14] In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN)[15] to catalogue and standardize proper names for stars. The WGSN approved the name Theemin for this star on February 1, 2017, and it is now included in the List of IAU-approved Star Names.[11]
In the Almagest, Ptolemy called it hē kampē, "the bend in the river;" Arab writers corrupted this to bhmn, later becoming beemin, beemun in the West. Subsequently, its etymology was incorrectly derived from Hebrew תאומים (te'omim), meaning "twins," producing Theemin.[16][17]
In Chinese, 天園 (Tiān Yuán), meaning Celestial Orchard, refers to an asterism consisting of Upsilon2 Eridani, Chi Eridani, Phi Eridani, Kappa Eridani, HD 16754, HD 23319, Theta Eridani, HD 24072, HD 24160, Upsilon4 Eridani, Upsilon3 Eridani and Upsilon1 Eridani.[18] Consequently, the Chinese name for Upsilon2 Eridani itself is 天園十二 (Tiān Yuán shíèr, English: the Twelfth Star of Celestial Orchard).[19]
References
edit- ^ a b c d e f van Leeuwen, F. (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, S2CID 18759600.
- ^ a b c d Gutierrez-Moreno, Adelina; et al. (1966), "A System of photometric standards", Publications of the Department of Astronomy University of Chile, 1, Publicaciones Universidad de Chile, Department de Astronomy: 1–17, Bibcode:1966PDAUC...1....1G.
- ^ a b Keenan, P.; McNeil, R. (October 1989), "The Perkins catalog of revised MK types for the cooler stars", Astrophysical Journal Supplement Series, 71: 245–266, Bibcode:1989ApJS...71..245K, doi:10.1086/191373.
- ^ de Bruijne, J. H. J.; Eilers, A.-C. (October 2012), "Radial velocities for the HIPPARCOS-Gaia Hundred-Thousand-Proper-Motion project", Astronomy & Astrophysics, 546: 14, arXiv:1208.3048, Bibcode:2012A&A...546A..61D, doi:10.1051/0004-6361/201219219, S2CID 59451347, A61.
- ^ Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", Astronomy Letters, 38 (5): 331, arXiv:1108.4971, Bibcode:2012AstL...38..331A, doi:10.1134/S1063773712050015, S2CID 119257644.
- ^ a b Lang, Kenneth R. (2006), Astrophysical formulae, Astronomy and astrophysics library, vol. 1 (3rd ed.), Birkhäuser, ISBN 3-540-29692-1. The radius (R*) is given by:
- ^ a b McDonald, I.; et al. (2012), "Fundamental Parameters and Infrared Excesses of Hipparcos Stars", Monthly Notices of the Royal Astronomical Society, 427 (1): 343–57, arXiv:1208.2037, Bibcode:2012MNRAS.427..343M, doi:10.1111/j.1365-2966.2012.21873.x, S2CID 118665352.
- ^ a b c d Alves, S.; et al. (April 2015), "Determination of the spectroscopic stellar parameters for 257 field giant stars", Monthly Notices of the Royal Astronomical Society, 448 (3): 2749–2765, arXiv:1503.02556, Bibcode:2015MNRAS.448.2749A, doi:10.1093/mnras/stv189, S2CID 119217930.
- ^ "ups02 Eri -- Star", SIMBAD Astronomical Database, Centre de Données astronomiques de Strasbourg, retrieved 2016-10-13.
- ^ 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.
- ^ a b "Naming Stars". IAU.org. Retrieved 16 December 2017.
- ^ Alves, David R. (August 2000), "K-Band Calibration of the Red Clump Luminosity", The Astrophysical Journal, 539 (2): 732–741, arXiv:astro-ph/0003329, Bibcode:2000ApJ...539..732A, doi:10.1086/309278, S2CID 16673121.
- ^ Richichi, A.; et al. (February 2005), "CHARM2: An updated Catalog of High Angular Resolution Measurements", Astronomy and Astrophysics, 431 (2): 773–777, Bibcode:2005A&A...431..773R, doi:10.1051/0004-6361:20042039.
- ^ Hough, Carole, ed. (2016), The Oxford Handbook of Names and Naming, Oxford University Press, p. 762, ISBN 978-0191630422.
- ^ "International Astronomical Union | IAU". www.iau.org. Retrieved 2017-03-31.
- ^ "Theemin". www.constellationsofwords.com.
- ^ Hough, Carole (May 3, 2016). The Oxford Handbook of Names and Naming. Oxford University Press. ISBN 9780191630422 – via Google Books.
- ^ (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.
