Binary star in the constellation Ursa Major
Tau Ursae Majoris Location of τ Ursae Majoris (circled)
Observation dataEpoch J2000.0 Equinox J2000.0 (ICRS ) Constellation Ursa Major Right ascension 09h 10m 55.06553s [ 1] Declination +63° 30′ 49.0553″[ 1] Apparent magnitude (V)4.66[ 2] Characteristics Spectral type kA5hF0mF5 II[ 3] U−Bcolor index +0.14[ 2] B−Vcolor index +0.35[ 2] Astrometry Radial velocity (Rv )± 0.30[ 4] km/s Proper motion (μ)RA: +102.37[ 1] mas /yr Dec.: −63.55[ 1] mas /yr Parallax (π)25.82± 0.54 mas [ 1] Distance 126 ± 3 ly pc ) Absolute magnitude (MV )+1.73[ 5] Orbit [ 6] Period (P)1,062.4 d Eccentricity (e)0.48 Periastron epoch (T)2425721.6 JD Argument of periastron (ω)349.4° Semi-amplitude 1 )3.9 km/s Details τ UMa A Mass ± 0.1[ 7] M ☉ Luminosity 16[ 8] L ☉ Surface gravity (log g )± 0.43[ 9] cgs Temperature ± 100[ 9] K Metallicity [Fe/H] ± 0.15[ 9] dex Rotational velocity (v sin i )21[ 10] Other designations τ UMa ,14 Ursae Majoris,BD +64°723,FK5 2727,HD 78362,HIP 45075,HR 3624,SAO 14796,WDS J09109+6331A[ 11] Database references SIMBAD data
Tau Ursae Majoris (τ UMa ) is theBayer designation for abinary star in the northerncircumpolar constellation ofUrsa Major . It is visible to the naked eye, having anapparent visual magnitude of 4.66.[ 2] parallax shift of 25.82 mas ,[ 1] light years from theSun . At that distance, the visual magnitude is diminished by anextinction factor of 0.19 due tointerstellar dust .[ 9]
This is a single-linedspectroscopic binary star system with anorbital period of 2.9 years and aneccentricity of 0.48.[ 6] evolved bright giant with astellar classification of kA5hF0mF5 II.[ 3] spectrum shows thecalcium K lines of an A5 star, the hydrogen lines of an F0 star, and the metallic lines of an F5 star.[ 12] Am star of theρ Puppis type , a class of evolved stars showing the Am chemical peculiarities.[ 13] instability strip of theHertzsprung–Russell diagram but is not thought to be variable.[ 7]
Withφ ,h ,υ ,θ ,e , andf , it composed the Arabicasterism Sarīr Banāt al-Na'sh , the Throne of the daughters ofNa'sh , andAl-H aud , the Pond.[ 14] Technical Memorandum 33-507 - A Reduced Star Catalog Containing 537 Named Stars ,Al-H aud were the title for seven stars :f asAlhaud I , this star (τ) asAlhaud II ,e asAlhaud III ,h asAlhaud IV ,θ asAlhaud V ,υ asAlhaud VI andφ asAlhaud VII .[ 15]
^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 Mermilliod, J.-C. (1986), "Compilation of Eggen's UBV data, transformed to UBV (unpublished)",Catalogue of Eggen's UBV Data ,SIMBAD ,Bibcode :1986EgUBV........0M . ^a b Gray, R. O.; et al. (July 2006), "Contributions to the Nearby Stars (NStars) Project: spectroscopy of stars earlier than M0 within 40 pc-The Southern Sample",The Astronomical Journal 132 (1):161– 170,arXiv :astro-ph/0603770 Bibcode :2006AJ....132..161G ,doi :10.1086/504637 ,S2CID 119476992 . ^ 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 Pourbaix, D.; Tokovinin, A. A.; Batten, A. H.; Fekel, F. C.; Hartkopf, W. I.; et al. (2004), "SB9 : The ninth catalogue of spectroscopic binary orbits",Astronomy & Astrophysics ,424 (2):727– 732,arXiv :astro-ph/0406573 Bibcode :2004A&A...424..727P ,doi :10.1051/0004-6361:20041213 ,S2CID 119387088 . ^a b Burkhart, C.; et al. (January 2005), "The field Am and ρ Puppis-like stars: Lithium and heavier elements",Astronomy and Astrophysics ,429 (3):1043– 1049,Bibcode :2005A&A...429.1043B ,doi :10.1051/0004-6361:20040467 ^ 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 Koleva, M.; Vazdekis, A. (February 2012), "Stellar population models in the UV. I. Characterisation of the New Generation Stellar Library",Astronomy & Astrophysics ,538 : A143,arXiv :1111.5449 Bibcode :2012A&A...538A.143K ,doi :10.1051/0004-6361/201118065 ,S2CID 53999614 . ^ Royer, F.; et al. (October 2002), "Rotational velocities of A-type stars in the northern hemisphere. II. Measurement of v sin i",Astronomy and Astrophysics ,393 :897– 911,arXiv :astro-ph/0205255 Bibcode :2002A&A...393..897R ,doi :10.1051/0004-6361:20020943 ,S2CID 14070763 . ^ "tau UMa" .SIMBAD Centre de données astronomiques de Strasbourg . Retrieved2017-02-25 .{{cite web }}: CS1 maint: postscript (link )^ Gray, Richard O.; Corbally, J. (2009),Stellar Spectral Classification ,Princeton University Press , p. 178,ISBN 978-0691125114 ^ Zaremba, D. (1979), "On the determination of the stellar chemical composition. I - Tau UMa",Acta Astronomica ,29 (4):573– 586,Bibcode :1979AcA....29..573Z . ^ Allen, Richard Hinckley (1899),Star-Names and Their Meanings , New York: G. E. Stechert, p. 442.^ Rhoads, Jack W. (November 15, 1971),Technical Memorandum 33-507-A Reduced Star Catalog Containing 537 Named Stars (PDF) , Jet Propulsion Laboratory, California Institute of Technology.
