Nu Ursae Majoris
 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[1] mas |
| Distance | 399 ± 8 ly (122 ± 3 pc) |
| Absolute magnitude (MV) | −2.47 ± 0.16[5] |
| Details | |
| Radius | 57.07 ± 4.13[5] R☉ |
| Surface gravity (log g) | 1.89[5] |
| Luminosity | 775 ± 122[5] L☉ |
| Temperature | 4,070[5] K |
| Metallicity [Fe/H] | –0.04[5] dex |
| Rotational velocity (v sin i) | 10[6] km/s |
| Other designations | |
Nu Ursae Majoris (ν UMa, ν Ursae Majoris) 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.
The proper name Alula Borealis (and erroneously Alula Boreale[10]) means "the Northern (star) of Alula." The words Alula and el-Awla[11] (with ξ) come from the Arabic phrase (al-Qafzah) al-Ūlā meaning "the first (leap)" (plus "Borealis", "northern" in Latin). It and Xi Ursae Majoris are Hea Tae （下台）, the Lower Dignitary, in Chinese astronomy.[12]
[edit] References
- ^ a b c d e f van Leeuwen, F. (November 2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics 474 (2): 653–664, Bibcode 2007A&A...474..653V, doi:10.1051/0004-6361:20078357
- ^ 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
- ^ 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
- ^ 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, Bibcode 2005A&A...430..165F, doi:10.1051/0004-6361:20041272
- ^ 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, Bibcode 2011A&A...526A.100P, doi:10.1051/0004-6361/201014442
- ^ 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
- ^ "54 UMa -- Star in double system", SIMBAD (Centre de Données astronomiques de Strasbourg), http://simbad.u-strasbg.fr/simbad/sim-id?Ident=HD+98262, retrieved 2012-01-11
- ^ Piazzi, G., The Palermo Catalogue, Palermo, 1814.
- ^ "The Colour of Stars", Australia Telescope, Outreach and Education (Commonwealth Scientific and Industrial Research Organisation), December 21, 2004, http://outreach.atnf.csiro.au/education/senior/astrophysics/photometry_colour.html, retrieved 2012-01-16
- ^ Bečvář, A., Atlas Coeli (Atlas of the Heavens) II - Catalogue, Plague, 1964.
- ^ Bode J., Uranographia, Berlin, 1801.
- ^ Allen, Richard Hinckley (1899), Star-Names and Their Meanings, New York: G. E. Stechert, p. 43
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