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Suggest pagesBeta Ursae Minoris
 Location of β Ursae Minoris (circled) |
|
| Observation data Epoch J2000 Equinox J2000 |
|
|---|---|
| Constellation | Ursa Minor |
| Right ascension | 14h 50m 42.32580s[1] |
| Declination | +74° 09′ 19.8142″[1] |
| Apparent magnitude (V) | 2.07[2] |
| Characteristics | |
| Spectral type | K4 III[2] |
| U−B color index | 1.77 |
| B−V color index | 1.47[2] |
| Astrometry | |
| Radial velocity (Rv) | +16.96[3] km/s |
| Proper motion (μ) | RA: -32.61[1] mas/yr Dec.: +11.42[1] mas/yr |
| Parallax (π) | 24.91 ± 0.12[1] mas |
| Distance | 130.9 ± 0.6 ly (40.1 ± 0.2 pc) |
| Details | |
| Mass | 2.8[4] M☉ |
| Radius | 42.06 ± 0.91[5] R☉ |
| Surface gravity (log g) | 1.83[5] |
| Luminosity | 390 ± 25[5] L☉ |
| Temperature | 4,030[5] K |
| Metallicity [Fe/H] | –0.29[5] dex |
| Rotational velocity (v sin i) | 8[6] km/s |
| Other designations | |
Beta Ursae Minoris (β UMi, β Ursae Minoris) is the brightest star in the bowl of the "Little Dipper" (which is part of the constellation Ursa Minor), and only slightly fainter than Polaris, the northern pole star and brightest star in Ursa Minor. It has the traditional name Kochab. Kochab's magnitude is 2.07.[2] It is 16 degrees from Polaris. The star is an orange giant and is 126.4 ± 2.5 light years from Earth.[2] It is 130 times more luminous than the Sun. Kochab has a surface temperature of approximately 4,000 K.
Kochab and its neighbor Pherkad are both naked eye stars and are sometimes referred to as the "Guardians of the Pole". They served as twin pole stars, Earth's North pole stars, from 1500 BC until 500 AD. 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 unclear. It comes from the Hebrew word for star, "kokhav"[8], כוכב. It appears to be cognate with Arabic الكوكب al-kawkab "the star", short for الكوكب الشمالي al-kawkab al-šamāliyy "the north star" (lit. heavenly body), named when it was still the pole star.
In Chinese, 北極 (Běi Jí), meaning North Pole, refers to an asterism consisting of β Ursae Minoris, γ Ursae Minoris, 5 Ursae Minoris, 4 Ursae Minoris and Σ 1694.[9] Consequently, β Ursae Minoris itself is known as 北極二 (Běi Jí èr, English: the Second Star of North Pole.),[10] representing 帝 (Dì), meaning Emperor.[11]
[edit] References
- ^ a b c d e van Leeuwen, F. (November 2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics 474 (2): 653–664, Bibcode 2007A&A...474..653V, doi:10.1051/0004-6361:20078357
- ^ a b c d e eSky. "Kochab (Beta Ursae Minoris)". http://www.glyphweb.com/esky/stars/kochab.html. Retrieved 2008-02-21.
- ^ 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, Bibcode 2005A&A...430..165F, doi:10.1051/0004-6361:20041272
- ^ Gondoin, P. (December 1999), "Evolution of X-ray activity and rotation on G-K giants", Astronomy and Astrophysics 352: 217–227, Bibcode 1999A&A...352..217G
- ^ a b c d e Piau, L. et al. (February 2011), "Surface convection and red-giant radius measurements", Astronomy and Astrophysics 526: A100, Bibcode 2011A&A...526A.100P, doi:10.1051/0004-6361/201014442
- ^ 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
- ^ "KOCHAB -- Variable Star", SIMBAD (Centre de Données astronomiques de Strasbourg), http://simbad.u-strasbg.fr/simbad/sim-id?Ident=Beta+Ursae+Minoris, retrieved 2012-01-11
- ^ "Star in Proto-Semitic language". http://en.wiktionary.org/wiki/Appendix:Proto-Semitic/kabkab-. Retrieved 15 September 2011.
- ^ (Chinese) 中國星座神話, written by 陳久金. Published by 台灣書房出版有限公司, 2005, ISBN 978-986-7332-25-7.
- ^ (Chinese)http://zh.wikipedia.org/wiki/%E5%8C%97%E6%A5%B5_%28%E6%98%9F%E5%AE%98%29
- ^ (Chinese) 香港太空館 - 研究資源 - 亮星中英對照表, Hong Kong Space Museum. Accessed on line November 23, 2010.
[edit] Further reading
- Beyer Steven L., The Star Guide, Little, Brown and Company, 1986.
- Mythology: Bx Times Reporter, New York
| Preceded by Thuban |
Pole Star 1900 BC–500 |
Succeeded by Polaris |
Coordinates: 
14h 50m 42.3s, +74° 09′ 20″
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