Upsilon2 Eridani

υ2 Eridani
Location of υ2 Eridani (circled)
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Eridanus
Right ascension 04h 35m 33.03796s
Declination −30° 33′ 44.4313″
Apparent magnitude (V) 3.804
Characteristics
Evolutionary stage Red clump
Spectral type G8+ III
U−B color index +0.740
B−V color index +0.968
Astrometry
Radial velocity (Rv)−4.0±0.9 km/s
Proper motion (μ) RA: −49.422 mas/yr
Dec.: −12.543 mas/yr
Parallax (π)15.4501±0.1081 mas
Distance211 ± 1 ly
(64.7 ± 0.5 pc)
Absolute magnitude (MV)−0.139±0.033
Details
Mass3.15±0.13 M☉
Radius14.09±0.34 R☉
Luminosity114±4 L☉
Surface gravity (log g)2.570±0.084 cgs
Temperature5,023±42 K
Metallicity [Fe/H]0.018±0.037 dex
Other designations
Theemin, υ2 Eridani, Upsilon2 Eridani, 52 Eridani, CD−30°1901, CPD−30°631, FK5 170, GC 5614, HD 29291, HIP 21393, HR 1464, PPM 280424, SAO 195148
Database references
SIMBADdata

Upsilon2 Eridani (υ² Eridani, abbreviated Upsilon2 Eri, υ2 Eri), officially named Theemin /ˈθiːmən/, is a star in the constellation of Eridanus. It is visible to the naked eye with an apparent visual magnitude of 3.8. Based upon parallax measurements obtained during the Gaia mission, it is approximately 211 light-years distant.

It is an evolved red clump giant star with a stellar classification of G8+ III. The star has 3.15 times the Sun's mass and 14.09 times the Sun's radius. It radiates 114 times the solar luminosity from its outer atmosphere at an effective temperature of 5,023 K.

Nomenclature

υ2 Eridani (Latinised to Upsilon2 Eridani) is the star's Bayer designation.

It bore the traditional name Theemin (also written as Theemim and Beemin). In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN) 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.

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.

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. Consequently, the Chinese name for Upsilon2 Eridani itself is 天園十二 (Tiān Yuán shíèr, English: the Twelfth Star of Celestial Orchard).

References

  1. 1 2 3 4 5 6 Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv:2208.00211. Bibcode:2023A&A...674A...1G. doi:10.1051/0004-6361/202243940. S2CID 244398875. Gaia DR3 record for this source at VizieR.
  2. 1 2 3 4 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.
  3. 1 2 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.
  4. 1 2 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.
  5. ↑ 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.
  6. 1 2 3 Ottoni, G.; Udry, S.; Ségransan, D.; Buldgen, G.; Lovis, C.; Eggenberger, P.; Pezzotti, C.; Adibekyan, V.; Marmier, M.; Mayor, M.; Santos, N. C.; Sousa, S. G.; Lagarde, N.; Charbonnel, C. (2022-01-01), "CORALIE radial-velocity search for companions around evolved stars (CASCADES). I. Sample definition and first results: Three new planets orbiting giant stars", Astronomy and Astrophysics, 657: A87, arXiv:2201.01528, Bibcode:2022A&A...657A..87O, doi:10.1051/0004-6361/202040078, ISSN 0004-6361.
  7. ↑ "ups02 Eri -- Star", SIMBAD Astronomical Database, Centre de Données astronomiques de Strasbourg, retrieved 2016-10-13.
  8. ↑ 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.
  9. 1 2 "Naming Stars". IAU.org. Archived from the original on 10 March 2025. Retrieved 16 December 2017.
  10. ↑ Hough, Carole, ed. (2016), The Oxford Handbook of Names and Naming, Oxford University Press, p. 762, ISBN 978-0191630422.
  11. ↑ "International Astronomical Union | IAU". www.iau.org. Archived from the original on 2020-05-13. Retrieved 2017-03-31.
  12. ↑ "Theemin". www.constellationsofwords.com.
  13. ↑ Hough, Carole (May 3, 2016). The Oxford Handbook of Names and Naming. Oxford University Press. ISBN 9780191630422 – via Google Books.
  14. ↑ (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.
  15. ↑ (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.