Nu Ursae Majoris

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Nu Ursae Majoris
Diagram showing star positions and boundaries of the Ursa Major constellation and its surroundings
Diagram showing star positions and boundaries of the Ursa Major constellation and its surroundings

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]
Database references

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:0708.1752free to read, 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, doi:10.1093/mnras/172.3.667 
  3. ^ a b Morgan, W. W.; Keenan, P. C. (1973), "Spectral Classification", Annual Review of Astronomy and Astrophysics, 11: 29–50, 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/0409579free to read, 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:1010.3649free to read, 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