Beta Ursae Minoris

Beta Ursae Minoris
Diagram showing star positions and boundaries of the Ursa Minor constellation and its surroundings
Cercle rouge 100%.svg
Location of β Ursae Minoris (circled)
Observation data
Epoch J2000      Equinox J2000
ConstellationUrsa Minor
Right ascension14h 50m 42.32580s[1]
Declination+74° 09′ 19.8142″[1]
Apparent magnitude (V)2.08[2]
Characteristics
Spectral typeK4 III[3]
U−B color index+1.78[2]
B−V color index+1.47[2]
Astrometry
Radial velocity (Rv)+16.96[4] 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
Distance130.9 ± 0.6 ly
(40.1 ± 0.2 pc)
Absolute magnitude (MV)−0.83±0.010[5]
Details
Mass2.2 ± 0.3[6] M
Radius42.06 ± 0.91[7] R
Luminosity390 ± 25[7] L
Surface gravity (log g)1.83[7] cgs
Temperature4,030[7] K
Metallicity [Fe/H]–0.29[7] dex
Rotational velocity (v sin i)8[8] km/s
Other designations
Kochab, Kocab, Kochah, 7 Ursae Minoris, Al Kaukab al Shamaliyy, BD+74 595, FK5 550, GCTP 3373.00, HD 131873, HIP 72607, HR 5563, SAO 8102.[9]
Database references
SIMBADdata

Beta Ursae Minoris (β Ursae Minoris, abbreviated Beta UMi, β UMi), also named Kochab,[10] 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.[2] 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).[1]

Amateur astronomers can use Kochab as a very precise guide for setting up a telescope, as the celestial north pole is located 43 arcminutes away from Polaris, very close to the line connecting Polaris with Kochab.[11]

Nomenclature

β Ursae Minoris (Latinised to Beta Ursae Minoris) is the star's Bayer designation.

It bore the traditional name Kochab which appeared in the Renaissance and its meaning is uncertain. It may be from Arabic الكوكب al-kawkab or Hebrew כוכב kōkhāv, both of which mean 'star', or more likely derived from Alrucaba or Rucaba, a name applied to Theta Ursae Majoris.[12] In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN)[13] to catalog and standardize proper names for stars. The WGSN's first bulletin of July 2016[14] included a table of the first two batches of names approved by the WGSN; which included Kochab for this star.

In Chinese, 北極 (Běi Jí), meaning North Pole, refers to an asterism consisting of Beta Ursae Minoris, Gamma Ursae Minoris, 5 Ursae Minoris, 4 Ursae Minoris and Σ 1694.[15] Consequently, Beta Ursae Minoris itself is known as 北極二 (Běi Jí èr, English: the Second Star of North Pole.),[16] representing (), meaning Emperor.[17]

Other Languages
العربية: كوكب (نجم)
asturianu: Kochab
беларуская: Кохаб
беларуская (тарашкевіца)‎: Кохаб
български: Кохаб
català: Kochab
čeština: Kochab
Deutsch: Kochab
Ελληνικά: Κοτσάμπ
español: Kochab
한국어: 코카브
italiano: Kochab
Lëtzebuergesch: Kochab (Stär)
Nederlands: Kocab
norsk nynorsk: Kochab
polski: Kochab
português: Beta Ursae Minoris
русский: Кохаб
slovenčina: Kochab
svenska: Kochab
татарча/tatarça: Акбүзат
中文: 北極二