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Dubhe

Dubhe
Location of Dubhe (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Ursa Major
Pronunciation /ˈdʌbiː/
Right ascension 11h 03m 43.67152s[1]
Declination +61° 45′ 03.7249″[1]
Apparent magnitude (V) 1.79[2] (1.87 + 4.85)[3]
Characteristics
Spectral type K0III[4] + A5V[3]
U−B color index +0.93[2]
B−V color index +1.07[2]
Variable type Suspected[5]
Astrometry
Radial velocity (Rv)−9.4±0.3[6] km/s
Proper motion (μ) RA: –134.11[1] mas/yr
Dec.: –34.70[1] mas/yr
Parallax (π)26.54 ± 0.48 mas[1]
Distance123 ± 2 ly
(37.7 ± 0.7 pc)
Absolute magnitude (MV)−1.10±0.04[7]
Orbit[3]
Companionα UMa B
Period (P)44.45±0.11 yr
Semi-major axis (a)0.590±0.026″
Eccentricity (e)0.439±0.004
Inclination (i)159.9±3.5°
Longitude of the node (Ω)9.3±8.2°
Periastron epoch (T)2,002.17±0.09
Argument of periastron (ω)
(secondary)		232.8±7.9°
Details
α UMa A
Mass3.7±0.4[3] M☉
Radius26.85[8] R☉
Luminosity339[9] L☉
Surface gravity (log g)2.22[3] cgs
Temperature4,650[3] K
Metallicity [Fe/H]–0.15[3] dex
Rotation<1.35[3] years
Rotational velocity (v sin i)2.63±0.15[3] km/s
Age280±30[10] Myr
α UMa B
Mass2.5±0.4[3] M☉
Other designations
Dubhe, Ak, α Ursae Majoris, α UMa, Alpha UMa, 50 UMa, NSV 5070, BD+62°1161, FK5 417, GC 15185, HD 95689, HIP 54061, HR 4301, SAO 15384, PPM 17705, ADS 8035, CCDM J11037+6145AB, WDS J11037+6145AB[11]
Database references
SIMBADdata

Dubhe is a multiple star system in the northern constellation of Ursa Major. It is formally designated Alpha Ursae Majoris, Latinised from α Ursae Majoris,[12][13] Despite being designated "α" (alpha), it is the second-brightest object in the constellation. Alpha Ursae Majoris is the northern of the 'pointers' (or 'guards'), the second being Beta Ursae Majoris, or 'Merak' – this pair of stars point towards Polaris, the North Star.[14] α Ursae Majoris is located at a distance of approximately 123 light years from the Sun, based on parallax measurements.

Although it is part of the constellation of Ursa Major, it is not part of the Ursa Major Moving Group of stars that have a common motion through space.[15]

  1. ^ a b c d e Cite error: The named reference aaa474_2_653 was invoked but never defined (see the help page).
  2. ^ a b c Cite error: The named reference clpl4_99 was invoked but never defined (see the help page).
  3. ^ a b c d e f g h i j Cite error: The named reference Gray2018 was invoked but never defined (see the help page).
  4. ^ Cite error: The named reference guenther was invoked but never defined (see the help page).
  5. ^ Samus, N. N.; Durlevich, O. V.; et al. (2009). "VizieR Online Data Catalog: General Catalogue of Variable Stars (Samus+ 2007-2013)". VizieR On-line Data Catalog: B/GCVS. Originally Published in: 2009yCat....102025S. 1. Bibcode:2009yCat....102025S.
  6. ^ Cite error: The named reference Gontcharov2006 was invoked but never defined (see the help page).
  7. ^ Cite error: The named reference aj135_3_892 was invoked but never defined (see the help page).
  8. ^ Cite error: The named reference gray2019 was invoked but never defined (see the help page).
  9. ^ Cite error: The named reference Luck2015 was invoked but never defined (see the help page).
  10. ^ Cite error: The named reference Baines_et_al_2017 was invoked but never defined (see the help page).
  11. ^ Cite error: The named reference SIMBAD was invoked but never defined (see the help page).
  12. ^ Cite error: The named reference Kunitzsch was invoked but never defined (see the help page).
  13. ^ "IAU Catalog of Star Names". Retrieved 28 July 2016.
  14. ^ Cite error: The named reference Streicher2009 was invoked but never defined (see the help page).
  15. ^ Motz, Lloyd; Nathanson, Carol (1988). The Constellations: An Enthusiast's Guide To The Night Sky. Doubleday. p. 39. ISBN 978-0385176002.

Dubhe

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