Beta Ursae Minoris

Coordinates: Sky map 14h 50m 42.3s, +74° 09′ 20″
Source: Wikipedia, the free encyclopedia.
Kochab
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) 2.08[2]
Characteristics
Spectral type K4 III[3]
U−B color index +1.78[2]
B−V color index +1.47[2]
Distance
130.9 ± 0.6 ly
(40.1 ± 0.2 pc)
Absolute magnitude (MV)−0.83±0.010[5]
Details
Gyr
PLX 3373.00[9]
Database references
SIMBADBeta Ursae Minoris

Kochab

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]

arcminutes away from Polaris, very close to the line connecting Polaris with Kochab.[12]

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

Working Group on Star Names (IAU-WGSN)[13] to catalog and standardize proper names for stars. The IAU-WGSN's first bulletin, July 2016,[14]
included a table of the first two batches of names approved by the IAU-WGSN, which included Kochab for this star.

In

Chinese name for Beta Ursae Minoris itself is 北極二 Běi Jí èr ('the Second Star of North Pole'), representing 帝 Dì ('emperor').[16]

Properties

This is a 'red'

K-type star.[18]

By modelling this star based upon

astroseismic frequencies depending sensitively on the star's mass. From this, a much lower mass estimate of 1.3 ± 0.3 M☉ is reached.[7]

As the pole star

From around 2500 

Ancient Egyptian astronomers as 'The Indestructibles' lighting the North.[19] As precession continued, by the year 1100 BCE, Kochab was within roughly 7° of the north celestial pole, with old references over-emphasizing this near pass by referring to Beta Ursae Minoris as "Polaris",[20] relating it to the current pole star, Polaris, which is slightly brighter and will have a much closer alignment of less than 0.5° by 2100 CE.[20]

This change in the identity of the pole stars is a result of Earth's axial precession. After 2000 BCE, Kochab and a new star, its neighbor Pherkad, were closer to the pole and together served as twin pole stars, circling the North Pole from around 1700 BCE until just after 300 CE. Neither star was as close to the north celestial pole as Polaris is now.[21] Today, they are sometimes referred to as the "Guardians of the Pole".[21]

Preceded by Pole star Succeeded by
Tau Herculis c. 1800 BC - 300 CE Polaris

Planetary system

Estimated to be around 2.95 billion years old, give or take 1 billion years, Kochab was announced to have a planetary companion around 6.1 times as

massive as Jupiter with an orbit of 522 days.[6]

The Kochab planetary system[22]
Companion
(in order from star) 		Mass Semimajor axis
(AU) 		Orbital period
(days) 		Eccentricity Inclination Radius
b ≥6.1 ± 1.0 MJ 1.4 ± 0.1 522.3 ± 2.7 0.19 ± 0.02 — —

References

  1. ^ a b c d e f van Leeuwen, F. (November 2007). "Validation of the new Hipparcos reduction".
    doi:10.1051/0004-6361:20078357
    .
  2. ^ a b c d Johnson, H.L.; Iriarte, B.; Mitchell, R.I.; Wisniewskj, W.Z. (1966). "UBVRIJKL photometry of the bright stars".
    Bibcode:1966CoLPL...4...99J
    .
  3. ^ a b Morgan, W.W.; Keenan, P.C. (September 1973). "Spectral Classification".
    doi:10.1146/annurev.aa.11.090173.000333
    .
  4. ^ Famaey, B.; Jorissen, A.; Luri, X.; Mayor, M.; Udry, S.; Dejonghe, H.; Turon, C. (12 January 2005). "Local kinematics of K and M giants from CORAVEL / Hipparcos / Tycho-2 data: Revisiting the concept of superclusters".
    doi:10.1051/0004-6361:20041272
    .
  5. ^ Park, Sunkyung; Kang, Wonseok; Lee, Jeong-Eun; Lee, Sang-Gak (21 August 2013). "Wilson-Bappu effect: Extended to surface gravity".
    doi:10.1088/0004-6256/146/4/73
    .
  6. ^ a b c d Lee, B.-C.; Han, I.; Park, M.-G.; Mkrtichian, D.E.; Hatzes, A.P.; Kim, K.-M. (June 2014). "Planetary companions in K giants β Cancri, μ Leonis, and β Ursae Minoris".
    doi:10.1051/0004-6361/201322608
    .
  7. ^ a b c Tarrant, N.J.; Chaplin, W.J.; Elsworth, Y.; Spreckley, S.A.; Stevens, I.R. (June 2008). "Oscillations in ß Ursae Minoris: Observations with SMEI".
    doi:10.1051/0004-6361:200809738
    .
  8. ^
    ISSN 1538-3881
    .
  9. ^ "bet UMi". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2012-01-11.
  10. ^ a b Kunitzsch, P.; Smart, T. (2006). A Dictionary of Modern Star Names: A short guide to 254 star names and their derivations (2nd, revised ed.). Sky Publishing.
    ISBN 1-931559-44-9
    .
  11. ^ IAU Catalog of Star Names (TXT) (Report). Archived from the original on 2016-08-12. Retrieved 28 July 2016.
  12. ^ "Geocentric Positions of Major Solar System Objects and Bright Stars". US Naval Observatory. Retrieved August 6, 2022.
  13. ^ "Division C WG Star Names". International Astronomical Union. Archived from the original on 2016-06-10. Retrieved 22 May 2016.
  14. ^ "Bulletin of the IAU Working Group on Star Names" (PDF). July 2016. Archived (PDF) from the original on 2016-09-09. Retrieved 28 July 2016.
  15. ^ zh:陳久金 [Chen, Jiujin] (December 2005). 中國星座神話 [Chinese Constellation Myths] (in Chinese). Taiwan: 台灣書房出版有限公司 [Taiwan Book Publishing Co. Ltd.]
    ISBN 978-986-7332-25-7.[page needed
    ]
  16. ^ "研究資源 – 亮星中英對照表" [Research resources – Chinese-English star name comparison table]. 香港太空館 [Hong Kong Space Museum] (in Chinese and English). Archived from the original on 2010-08-10. Retrieved 23 November 2010.
  17. ^ Williams, D.R. (1 July 2013). "Sun fact sheet".
    National Aeronautics and Space Administration. Archived
    from the original on 15 July 2010. Retrieved 12 August 2013.
  18. ^ "The colour of stars". Australia Telescope, Outreach and Education.
    Commonwealth Scientific and Industrial Research Organisation. 21 December 2004. Archived from the original
    on 2012-03-18. Retrieved 2012-01-16.
  19. ^ a b c "The planet Earth: Ancient astronomy calendars, navigation, predictions". Space Today, Online. 2006. Archived from the original on 2020-10-03.
  20. ^ a b Kaler, James B. (20 December 2013). "Kochab (Beta Ursae Minoris)". Astronomy. Stars. University of Illinois. Archived from the original on 2018-06-25. Retrieved 2018-04-28.
  21. ^ a b Benningfield, Damond (14 June 2015). Kochab.
    University of Texas. Archived from the original
    (.mp3) on 2015-09-04. Retrieved 14 June 2015.
  22. ^ Schneider, Jean. "Planet β Umi b". Extrasolar Planets Encyclopaedia. Archived from the original on 2017-03-12. Retrieved 8 March 2017.
Preceded by
1900 BC–500 BC
 Succeeded by


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