Beta Ursae Minoris
Kochab /ˈkoʊkæb/, Bayer designation Beta Ursae Minoris (β Ursae Minoris, abbreviated β UMi, Beta UMi), is the brightest star in the bowl of the Little Dipper asterism (which is part of the constellation of Ursa Minor), and only slightly fainter than Polaris, the northern pole star and brightest star in Ursa Minor. Kochab is 16 degrees from Polaris and has an apparent visual magnitude of 2.08. The distance to this star from the Sun can be deduced from the parallax measurements made during the Hipparcos mission, yielding a value of 130.9 light-years (40.1 parsecs).
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Ursa Minor |
| Right ascension | 14h 50m 42.32580s |
| Declination | +74° 09′ 19.8142″ |
| Apparent magnitude (V) | 2.08 |
| Characteristics | |
| Spectral type | K4 III |
| U−B color index | +1.78 |
| B−V color index | +1.47 |
| Astrometry | |
| Radial velocity (Rv) | +16.96 km/s |
| Proper motion (μ) | RA: −32.61 mas/yr Dec.: +11.42 mas/yr |
| Parallax (π) | 24.91 ± 0.12 mas |
| Distance | 130.9 ± 0.6 ly (40.1 ± 0.2 pc) |
| Absolute magnitude (MV) | −0.83±0.010 |
| Details | |
| Mass | 2.2 ± 0.3 M☉ |
| Radius | 42.06 ± 0.91 R☉ |
| Luminosity | 390 ± 25 L☉ |
| Surface gravity (log g) | 1.83 cgs |
| Temperature | 4,030 K |
| Metallicity [Fe/H] | –0.29 dex |
| Rotational velocity (v sin i) | 8 km/s |
| Other designations | |
| Database references | |
| SIMBAD | Beta Ursae Minoris |
Amateur astronomers can use Kochab as a precise guide for equatorial mount alignment: The celestial north pole is located 38 arcminutes away from Polaris, very close to the line connecting Polaris with Kochab.