Star in the constellation of Eridanus
υ2 Eridani Location of υ
2 Eridani (circled)
Observation dataEpoch 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 Evolutionary stage red clump [ 3] Spectral type G8+ III[ 4] U−Bcolor index +0.740[ 2] B−Vcolor index +0.968[ 2] Astrometry Radial velocity (Rv )± 0.9[ 5] 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 pc ) Absolute magnitude (MV )−0.27[ 6] Details Radius 16[ 7] R ☉ Luminosity 138[ 8] L ☉ Surface gravity (log g )± 0.07[ 9] cgs Temperature ± 30[ 9] K Metallicity ± 0.03[ 9] 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.[ 10] Database references SIMBAD data
Upsilon2 Eridani (υ² Eridani , abbreviatedUpsilon2 Eri ,υ2 Eri ), officially namedTheemin /ˈ θ iː m ə n [ 11] [ 12] star in theconstellation ofEridanus . It is visible to the naked eye with anapparent visual magnitude of 3.8.[ 2] parallax measurements obtained during theHipparcos mission,[ 1] parsecs (214light-years ) from theSun .
It is anevolved red clump [ 3] giant star with astellar classification of G8+ III.[ 4] angular diameter is 2.21 mas .[ 13] radius of the Sun .[ 7] [ 8] solar luminosity from itsouter atmosphere at aneffective temperature of 5074 K.[ 9]
υ2 Eridani (Latinised toUpsilon2 Eridani ) is the star'sBayer designation .
It bore the traditional nameTheemin (also written asTheemim andBeemin ).[ 14] International Astronomical Union organized aWorking Group on Star Names (WGSN)[ 15] Theemin for this star on February 1, 2017, and it is now included in the List of IAU-approved Star Names.[ 12]
In theAlmagest , Ptolemy called ithē kampē , "the bend in the river;" Arab writers corrupted this tobhmn , later becomingbeemin ,beemun in the West. Subsequently, its etymology was incorrectly derived from Hebrew תאומים (te'omim ), meaning "twins," producingTheemin .[ 16] [ 17]
InChinese ,天園 Tiān Yuán Celestial Orchard 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 andUpsilon1 Eridani .[ 18] Chinese name for Upsilon2 Eridani itself is天園十二 Tiān Yuán shíèr the Twelfth Star of Celestial Orchard ).[ 19]
^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 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 . ^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 Birkhäuser ,ISBN 3-540-29692-1 * ) is given by:2 ⋅ R ∗ = ( 65.6 ⋅ 2.21 ⋅ 10 − 3 ) AU 0.0046491 AU / R ⨀ ≈ 31.2 ⋅ R ⨀ {\displaystyle {\begin{aligned}2\cdot R_{*}&={\frac {(65.6\cdot 2.21\cdot 10^{-3})\ {\text{AU}}}{0.0046491\ {\text{AU}}/R_{\bigodot }}}\\&\approx 31.2\cdot R_{\bigodot }\end{aligned}}} ^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, retrieved2016-10-13 .^ 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. Retrieved16 December 2017 .^ 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 . Retrieved2017-03-31 .^ "Theemin" .www.constellationsofwords.com .^ Hough, Carole (May 3, 2016).The Oxford Handbook of Names and Naming ISBN 9780191630422 ^ (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 theWayback Machine , Hong Kong Space Museum. Accessed on line November 23, 2010.
