Nu Ursae Majoris

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Nu Ursae Majoris
Diagram showing star positions and boundaries of the Andromeda constellation and its surroundings
Cercle rouge 100%.svg

Location of ν Ursae Majoris (circled)
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Ursa Major
Right ascension 11h 18m 28.73664s[1]
Declination +33° 05′ 39.5107″[1]
Apparent magnitude (V) +3.490[2]
Spectral type K3 III[3]
U−B color index +1.550[2]
B−V color index +1.400[2]
Radial velocity (Rv) -9.63 ± 0.38[4] km/s
Proper motion (μ) RA: –26.84[1] mas/yr
Dec.: +28.69[1] mas/yr
Parallax (π) 8.17 ± 0.17[1] mas
Distance 399 ± 8 ly
(122 ± 3 pc)
Absolute magnitude (MV) −2.47 ± 0.16[5]
Radius 57.07 ± 4.13[5] R
Luminosity 775 ± 122[5] L
Surface gravity (log g) 1.89[5] cgs
Temperature 4,070[5] K
Metallicity [Fe/H] –0.04[5] dex
Rotational velocity (v sin i) 10[6] km/s
Other designations
Alula Borealis, ν Ursae Majoris, ν UMa, Nu UMa, 54 Ursae Majoris, BD+33 2098, CCDM J11185+3306A, FK5 425, GC 15547, HD 98262, HIP 55219, HR 4377, IDS 11131+3338 A, PPM 75790, SAO 62486, WDS J11185+3306A [7]

Nu Ursae Majoris (Nu UMa, ν Ursae Majoris, ν UMa) is a double star in the northern circumpolar constellation of Ursa Major. The traditional name of this star is Alula Borealis.[8] At an apparent visual magnitude of +3.490,[2] it is bright enough to be seen with the naked eye. Based upon parallax measurements, the distance to ν Ursae Majoris is about 399 light-years (122 parsecs).[1]

This is a giant star with a stellar classification of K3 III.[3] It has expanded to about 57 times the radius of the Sun and is radiating 775 times the Sun's luminosity.[5] The effective temperature of the outer envelope is 4,070 K;[5] cool enough to give it an orange hue typical of a K-type star.[9] It has a 10th-magnitude optical companion at an angular separation of 7.1 arcseconds.

Name and etymology[edit]


  1. ^ a b c d e f van Leeuwen, F. (November 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 
  2. ^ a b c d Jennens, P. A.; Helfer, H. L. (September 1975), "A new photometric metal abundance and luminosity calibration for field G and K giants.", Monthly Notices of the Royal Astronomical Society 172: 667–679, Bibcode:1975MNRAS.172..667J 
  3. ^ a b Morgan, W. W.; Keenan, P. C. (1973), "Spectral Classification", Annual Review of Astronomy and Astrophysics 11: 29, Bibcode:1973ARA&A..11...29M, doi:10.1146/annurev.aa.11.090173.000333 
  4. ^ Famaey, B. et al. (January 2005), "Local kinematics of K and M giants from CORAVEL/Hipparcos/Tycho-2 data. Revisiting the concept of superclusters", Astronomy and Astrophysics 430: 165–186, arXiv:astro-ph/0409579, Bibcode:2005A&A...430..165F, doi:10.1051/0004-6361:20041272 
  5. ^ a b c d e f g h Piau, L. et al. (February 2011), "Surface convection and red-giant radius measurements", Astronomy and Astrophysics 526: A100, arXiv:1010.3649, Bibcode:2011A&A...526A.100P, doi:10.1051/0004-6361/201014442 
  6. ^ Bernacca, P. L.; Perinotto, M. (1970), "A catalogue of stellar rotational velocities", Contributi Osservatorio Astronomico di Padova in Asiago 239 (1), Bibcode:1970CoAsi.239....1B 
  7. ^ "54 UMa -- Star in double system", SIMBAD (Centre de Données astronomiques de Strasbourg), retrieved 2012-01-11 
  8. ^ Piazzi, G., The Palermo Catalogue, Palermo, 1814.
  9. ^ "The Colour of Stars", Australia Telescope, Outreach and Education (Commonwealth Scientific and Industrial Research Organisation), December 21, 2004, retrieved 2012-01-16 
  10. ^ Richard Hinckley Allen :Star Names — Their Lore and Meaning - Ursa Major, the Greater Bear
  11. ^ (Chinese) (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 6 月 21 日