Nu Ursae Majoris

Nu Ursae Majoris

Location of ν Ursae Majoris (circled)
Observation data Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation	Ursa Major
Right ascension	11^h 18^m 28.73664^s[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☉
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
SIMBAD	data

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

• The traditional name Alula (shared with ξ UMa) comes from the Arabic phrase Al Ḳafzah al Ūla "the First Spring".^[10] The term Borealis meaning "the north side" in Latin.
• In Chinese, 三台 (Sān Tái), meaning Three Steps, refers to an asterism consisting of ν Ursae Majoris, ι Ursae Majoris, κ Ursae Majoris, λ Ursae Majoris, μ Ursae Majoris, and ξ Ursae Majoris. Consequently, ν Ursae Majoris itself is known as 三台五 (Sān Tái wu, English: the Fifth Star of Three Steps) and 下台一 (Xià Tái yī, English: Star of First Lower Step).^[11]

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
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: 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
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
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