Nu Ursae Majoris

Nu Ursae Majoris (ν Ursae Majoris, abbreviated Nu UMa, ν UMa), formally named Alula Borealis /əˈluːlə bɒriˈælɪs/,[8][9] is a double star in the northern circumpolar constellation of Ursa Major. 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]

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]
Characteristics
Spectral type K3 III[3]
U−B color index +1.550[2]
B−V color index +1.400[2]
Astrometry
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 mas[1]
Distance399 ± 8 ly
(122 ± 3 pc)
Absolute magnitude (MV)−2.47 ± 0.16[5]
Details
Radius57.07 ± 4.13[5] R☉
Luminosity775 ± 122[5] L☉
Surface gravity (log g)1.89[5] cgs
Temperature4,070[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
SIMBADdata

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.[10] It has a 10th-magnitude optical companion at an angular separation of 7.1 arcseconds.

Nomenclature

ν Ursae Majoris (Latinised to Nu Ursae Majoris) is the star's Bayer designation.

It also bore the traditional name of Alula Borealis.[11] Alula (shared with Xi Ursae Majoris) comes from the Arabic phrase Al Ḳafzah al Ūla 'the First Spring'.[12] and Borealis is Latin for 'northern'. In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN)[13] to catalog and standardize proper names for stars. The WGSN's first bulletin of July 2016[14] included a table of the first two batches of names approved by the WGSN; which included Alula Borealis for this star.

In Chinese, 三台 (Sān Tái), meaning Three Steps, refers to an asterism consisting of Nu Ursae Majoris, Iota Ursae Majoris, Kappa Ursae Majoris, Lambda Ursae Majoris, Mu Ursae Majoris, and Xi Ursae Majoris. Consequently, the Chinese name for Nu Ursae Majoris itself is 下台一 (Xià Tái yī, English: Star of First Lower Step).[15]

References
  1. 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, S2CID 18759600
  2. 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 (3): 667–679, Bibcode:1975MNRAS.172..667J, doi:10.1093/mnras/172.3.667
  3. 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/0409579, Bibcode:2005A&A...430..165F, doi:10.1051/0004-6361:20041272, S2CID 17804304
  5. 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, S2CID 118533297
  6. Bernacca, P. L.; Perinotto, M. (1970), "A catalogue of stellar rotational velocities", Contributi Osservatorio Astronomico di Padova in Asiago, 239 (1): 1, Bibcode:1970CoAsi.239....1B
  7. "54 UMa -- Star in double system", SIMBAD, Centre de Données astronomiques de Strasbourg, retrieved 2012-01-11
  8. 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.
  9. "IAU Catalog of Star Names". Retrieved 28 July 2016.
  10. "The Colour of Stars", Australia Telescope, Outreach and Education, Commonwealth Scientific and Industrial Research Organisation, December 21, 2004, archived from the original on December 3, 2013, retrieved 2012-01-16
  11. Piazzi, G., The Palermo Catalogue, Palermo, 1814.
  12. Richard Hinckley Allen :Star Names — Their Lore and Meaning - Ursa Major, the Greater Bear
  13. "IAU Working Group on Star Names (WGSN)". Retrieved 22 May 2016.
  14. "Bulletin of the IAU Working Group on Star Names, No. 1" (PDF). Retrieved 28 July 2016.
  15. (in Chinese) (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 6 月 21 日
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