Upsilon Ursae Majoris

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Upsilon Ursae Majoris
Diagram showing star positions and boundaries of the Ursa Major constellation and its surroundings
Cercle rouge 100%.svg

Location of υ Ursae Majoris (circled)
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Ursa Major
Right ascension 10h 53m 58.74035s[1]
Declination +43° 11′ 23.8483″[1]
Apparent magnitude (V) +3.79[2]
Spectral type F2 IV[3]
U−B color index +0.09[2]
B−V color index +0.29[2]
Radial velocity (Rv) 27.3±4.1[4] km/s
Proper motion (μ) RA: +42.97[1] mas/yr
Dec.: −23.62[1] mas/yr
Parallax (π) 13.24 ± 0.50[1] mas
Distance 246 ± 9 ly
(76 ± 3 pc)
υ UMa A
Mass 1.57[5] or 2.20[3] M
Radius 2.79±0.40[6] R
Luminosity 29.5[7] L
Surface gravity (log g) 3.79±0.14[5] cgs
Temperature 7,211±245[5] K
Rotation 1.2±0.30 d[6]
Rotational velocity (v sin i) 124.2[8] km/s
Age 1.168[5] Gyr
υ UMa B
Mass 0.44[3] M
Other designations
υ UMa, 29 Ursae Majoris, BD+59° 1268, FK5 368, HD 84999, HIP 48319, HR 3888, SAO 27401, WDS J09510+5902A.[9]

Upsilon Ursae Majoris (υ UMa) is the Bayer designation for a binary star[10] in the northern circumpolar constellation of Ursa Major. It is visible to the naked eye with an apparent visual magnitude of +3.79.[2] Based upon an annual parallax shift of 13.24 mas,[1] it is located roughly 246 light years from the Sun.

The primary member of the system, component A, is an F-type subgiant star. It is a Delta Scuti variable[6] with a period of 0.1327 days and an amplitude of 0.050 magnitude.[11] With an estimated age of 1.168[5] billion years, it is spinning rapidly with a projected rotational velocity of 124.2 km/s[8] and a rotation period of 1.2 days.[6] The star has about 1.57[5] times the mass of the Sun and 2.79[6] times the Sun's radius. (De Rosa and colleagues give a mass estimate of 2.20[3] times the Sun's mass.) It is radiating around 29.5[7] times the solar luminosity from its outer atmosphere at an effective temperature of 7,211 K.[5]

The companion, component B, is a magnitude +11.0 star.[10] As of 2008, it has an angular separation of 11.78 arc seconds along a position angle of 295.4°. This corresponds to a projected separation of 419.8 AU.[3] It has a mass around 40% that of the Sun.[3]



  1. ^ a b c d e f van Leeuwen, F. (2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, arXiv:0708.1752Freely accessible, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357. 
  2. ^ 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. 
  3. ^ a b c d e f De Rosa, R. J.; et al. (2013), "The VAST Survey - III. The multiplicity of A-type stars within 75 pc", Monthly Notices of the Royal Astronomical Society, 437 (2): 1216, arXiv:1311.7141Freely accessible, Bibcode:2014MNRAS.437.1216D, doi:10.1093/mnras/stt1932. 
  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, arXiv:1208.3048Freely accessible, Bibcode:2012A&A...546A..61D, doi:10.1051/0004-6361/201219219, A61. 
  5. ^ a b c d e f g David, Trevor J.; Hillenbrand, Lynne A. (2015), "The Ages of Early-Type Stars: Strömgren Photometric Methods Calibrated, Validated, Tested, and Applied to Hosts and Prospective Hosts of Directly Imaged Exoplanets", The Astrophysical Journal, 804 (2): 146, arXiv:1501.03154Freely accessible, Bibcode:2015ApJ...804..146D, doi:10.1088/0004-637X/804/2/146. 
  6. ^ a b c d e Korzennik, S. G.; et al. (April 1995), "Nightly variations of nonradial oscillations in the Delta Scuti star upsilon Ursae Majoris", Astrophysical Journal, Part 2 - Letters, 443 (1): L25−L28, Bibcode:1995ApJ...443L..25K, doi:10.1086/187827. 
  7. ^ a b Balona, L. A.; Dziembowski, W. A. (October 1999), "Excitation and visibility of high-degree modes in stars", Monthly Notices of the Royal Astronomical Society, 309 (1): 221–232, Bibcode:1999MNRAS.309..221B, doi:10.1046/j.1365-8711.1999.02821.x. 
  8. ^ a b Schröder, C.; Reiners, A.; Schmitt, J. H. M. M. (January 2009), "Ca II HK emission in rapidly rotating stars. Evidence for an onset of the solar-type dynamo", Astronomy and Astrophysics, 493 (3): 1099–1107, Bibcode:2009A&A...493.1099S, doi:10.1051/0004-6361:200810377. 
  9. ^ "ups UMa -- Variable Star of delta Sct type", SIMBAD Astronomical Database, Centre de Données astronomiques de Strasbourg, retrieved 2017-02-22. 
  10. ^ a b Eggleton, P. P.; Tokovinin, A. A. (September 2008), "A catalogue of multiplicity among bright stellar systems", Monthly Notices of the Royal Astronomical Society, 389 (2): 869–879, arXiv:0806.2878Freely accessible, Bibcode:2008MNRAS.389..869E, doi:10.1111/j.1365-2966.2008.13596.x. 
  11. ^ Rodríguez, E.; et al. (June 2000), "A revised catalogue of delta Sct stars", Astronomy and Astrophysics Supplement, 144: 469–474, Bibcode:2000A&AS..144..469R, doi:10.1051/aas:2000221. 
  12. ^ Allen, Richard Hinckley (1899), Star-Names and Their Meanings, New York: G. E. Stechert, p. 442. 
  13. ^ (Chinese) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 6 月 16 日