Dubhe
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Ursa Major |
| Pronunciation | /ˈdʌbiː/ |
| Right ascension | 11h 03m 43.67152s |
| Declination | +61° 45′ 03.7249″ |
| Apparent magnitude (V) | 1.79 (1.87 + 4.85) |
| Characteristics | |
| Spectral type | K0III + A5V |
| U−B color index | +0.93 |
| B−V color index | +1.07 |
| Variable type | Suspected |
| Astrometry | |
| Radial velocity (Rv) | −9.4±0.3 km/s |
| Proper motion (μ) | RA: –134.11 mas/yr Dec.: –34.70 mas/yr |
| Parallax (π) | 26.54±0.48 mas |
| Distance | 123 ± 2 ly (37.7 ± 0.7 pc) |
| Absolute magnitude (MV) | −1.10±0.04 |
| Orbit | |
| Companion | α 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 | |
| Mass | 3.7±0.4 M☉ |
| Radius | 27.33+0.49 −0.50 R☉ |
| Luminosity | 339 L☉ |
| Surface gravity (log g) | 2.22 cgs |
| Temperature | 4,810±22 K |
| Metallicity [Fe/H] | –0.15 dex |
| Rotation | <1.35 years |
| Rotational velocity (v sin i) | 2.63±0.15 km/s |
| Age | 280±30 Myr |
| α UMa B | |
| Mass | 2.5±0.4 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 | |
| Database references | |
| SIMBAD | data |
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, 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. 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.