Beta Ursae Minoris
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| Observation data Epoch J2000 |
|
|---|---|
| Constellation | Ursa Minor |
| Right ascension | 14h 50m 42.3s |
| Declination | +74° 09′ 20″ |
| Apparent magnitude (V) | 2.07 |
| Spectral Characteristics | |
| Spectral type | K4 III |
| U-B color index | 1.77 |
| B-V color index | 1.47 |
| Variable type | ? |
| Astrometry | |
| Radial velocity (Rv) | +16.8 km/s |
| Proper motion (μ) | RA: -32.29 mas/yr Dec.: 11.91 mas/yr |
| Parallax (π) | 25.79 ± 0.52 mas |
| Distance | 126 ± 3 ly (38.8 ± 0.8 pc) |
| Absolute magnitude (MV) | -0.88 |
| Physical Characteristics | |
| Mass | 4.4 M☉ |
| Radius | 41 R☉ |
| Luminosity | 500 L☉ |
| Temperature | 4,000 K |
| Metallicity | ? |
| Rotation | ~17 km/s. |
| Age | ? years |
| Other designations | |
Beta Ursae Minoris (β UMi / β Ursae Minoris) is the second brightest star in the bowl of the "Little Dipper," the constellation Ursa Minor. It also has the traditional name Kochab. Kochab's magnitude is 2.1. It is 16 degrees from Polaris. The star is a yellow giant and is 110 light years from Earth. It is 130 times more luminous than the Sun. Kochab has a surface temperature of approximately 4,000 K.
Kochab and its neighbor Pherkab are both naked-eye stars. They served as twin pole stars, Earth's North pole stars, from 1500 B.C. until 500 A.D. Neither star was as proximitous to the pole as Polaris is now. Due to precession of the equinoxes, the previous holder of the title was Thuban, and the next was the present-day Polaris. This succession of pole stars is a result of earth's precessional motion.
The origin of the name Kochab is indistinct. It has sometimes been associated with a Hebrew word for star. The name "Kochab" may originate from Arabic الكوكب al-kawkab and means simply "the star".
[edit] Reference
- Beyer Steven L., The Star Guide, Little, Brown and Company, 1986.
Kochab and mythology www.webspawner.com/users/cosmic/
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