Upsilon2 Eridani

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υ2 Eridani
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]
Spectral type G8+ III[3]
U−B color index +0.740[2]
B−V color index +0.968[2]
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[1] mas
Distance 214 ± 3 ly
(65.6 ± 0.8 pc)
Radius 16[5] R
Luminosity 138[6] L
Surface gravity (log g) 2.77±0.07[7] cgs
Temperature 5,074±30[7] K
Metallicity [Fe/H] 0.04±0.03[7] dex
Other designations
Theemim, Theemin, Beemin, υ2 Eri, Upsilon2 Eridani, Upsilon2 Eri, 52 Eridani, 52 Eri, CD −30° 1901, CPD−30 631, FK5 170, GC 5614, HD 29291, HIP 21393, HR 1464, PPM 280424, SAO 195148.[8]
Database references

Upsilon2 Eridani (Upsilon2 Eri, υ2 Eridani, υ2 Eri), also named Theemin[9], 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 an annual parallax shift of 0.01525″,[1] it is approximately 214 light-years from the Sun.

This is a evolved red clump[10] giant star with a stellar classification of G8+ III.[3] The measured angular diameter is 2.21 mas.[11] At an estimated distance of the star, this yields a physical size of around 16 times the radius of the Sun.[5] It radiates 138[6] times the solar luminosity from its outer atmosphere at an effective temperature of 5074 K.[7]


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)[12] to catalogue and standardize proper names for stars. The WGSN approved the name Theemin for this star on February 1st, 2017 and it is now so entered in the IAU Catalog of Star Names.[9]

In Chinese, 天園 (Tiān Yuán), meaning Celestial Orchard, refers to an asterism consisting of υ2 Eridani, χ Eridani, φ Eridani, κ Eridani, HD 16754, HD 23319, θ Eridani, HD 24072, HD 24160, υ4 Eridani, 43 Eridani and υ1 Eridani.[13] Consequently, υ2 Eridani itself is known as 天園十二 (Tiān Yuán shíèr, English: the Twelfth Star of Celestial Orchard.)[14]


  1. ^ a b c d e f van Leeuwen, F. (2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, Bibcode:2007A&A...474..653V, arXiv:0708.1752Freely accessible, doi:10.1051/0004-6361:20078357. 
  2. ^ a b c d 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. 
  3. ^ 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. 
  4. ^ 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, Bibcode:2012A&A...546A..61D, arXiv:1208.3048Freely accessible, doi:10.1051/0004-6361/201219219, A61. 
  5. ^ a b Lang, Kenneth R. (2006), Astrophysical formulae, Astronomy and astrophysics library, 1 (3rd ed.), Birkhäuser, ISBN 3-540-29692-1.  The radius (R*) is given by:
  6. ^ 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, Bibcode:2012MNRAS.427..343M, arXiv:1208.2037Freely accessible, doi:10.1111/j.1365-2966.2012.21873.x. 
  7. ^ 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, Bibcode:2015MNRAS.448.2749A, arXiv:1503.02556Freely accessible, doi:10.1093/mnras/stv189. 
  8. ^ "ups02 Eri -- Star", SIMBAD Astronomical Database, Centre de Données astronomiques de Strasbourg, retrieved 2016-10-13. 
  9. ^ a b "IAU-CSN". 
  10. ^ Alves, David R. (August 2000), "K-Band Calibration of the Red Clump Luminosity", The Astrophysical Journal, 539 (2): 732–741, Bibcode:2000ApJ...539..732A, arXiv:astro-ph/0003329Freely accessible, doi:10.1086/309278. 
  11. ^ Richichi, A.; et al. (February 2005), "CHARM2: An updated Catalog of High Angular Resolution Measurements", Astronomy and Astrophysics, 431: 773–777, Bibcode:2005A&A...431..773R, doi:10.1051/0004-6361:20042039. 
  12. ^ "International Astronomical Union | IAU". Retrieved 2017-03-31. 
  13. ^ (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.
  14. ^ (in Chinese) 香港太空館 - 研究資源 - 亮星中英對照表, Hong Kong Space Museum. Accessed on line November 23, 2010.