Chi Ursae Majoris

Chi Ursae Majoris or χ Ursae Majoris, formally named Taiyangshou /ˌtaɪˌjæŋˈʃoʊ/,[10] is a single[11] star in the northern circumpolar constellation of Ursa Major. The star has an orange hue and is visible to the naked eye at night with an apparent visual magnitude of 3.72.[2] It is located at a distance of approximately 184 light-years from the Sun based on parallax, but is drifting closer with a radial velocity of −9 km/s.[2]

Chi Ursae Majoris
Location of χ Ursae Majoris (circled)
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Ursa Major
Right ascension 11h 46m 3.01407s[1]
Declination +47° 46′ 45.8626″[1]
Apparent magnitude (V) 3.72[2]
Characteristics
Evolutionary stage Horizontal branch[3]
Spectral type K0.5 IIIb[4]
U−B color index +1.16[2]
B−V color index +1.18[2]
Astrometry
Radial velocity (Rv)−9.02±0.20[2] km/s
Proper motion (μ) RA: −138.29[1] mas/yr
Dec.: 28.57[1] mas/yr
Parallax (π)17.76 ± 0.16 mas[1]
Distance184 ± 2 ly
(56.3 ± 0.5 pc)
Absolute magnitude (MV)0.10±0.02[5]
Details[2]
Mass1.49[6] M☉
Radius20.8±0.8[7] R☉
Luminosity158 L☉
Surface gravity (log g)2.2 cgs
Temperature4,416±9 K
Metallicity [Fe/H]−0.44 dex
Rotational velocity (v sin i)2.3 km/s
Other designations
Alkaphrah[8], El Koprah[8], Taiyangshou, Chi UMa, χ UMa, 63 Ursae Majoris, BD+48°1966, FK5 441, HD 102224, HIP 57399, HR 4518, SAO 43886[9]
Database references
SIMBADdata

Nomenclature
Chi Ursae Majoris and NGC 3877

χ Ursae Majoris (Latinised to Chi Ursae Majoris) is the star's Bayer designation.

It bore the traditional name Tai Yang Show, "the Sun Governor", from Chinese astronomy.[12] The name was possibly derived from the word 太陽守, Pinyin: Tàiyángshǒu, meaning Guard of the Sun, because this star is marking itself and standing alone in the Guard of the Sun asterism, Purple Forbidden enclosure (see : Chinese constellations). It also bore traditional names of Arabic origin: Alkafzah, Alkaphrah, and El Koprah.[8]

In 2016, the IAU organized a Working Group on Star Names (WGSN)[13] to catalog and standardize proper names for stars. The WGSN approved the name Taiyangshou for this star on 30 June 2017 and it is now so included in the List of IAU-approved Star Names.[10]

Properties

Chi Ursae Majoris is an evolved, orange hued K-type giant with a stellar classification of K0.5 IIIb.[4] It is a red clump giant,[3] which means it is on the horizontal branch and is generating energy through helium fusion at its core. This star has expanded to 20.8±0.8[7] times the radius of the Sun with 1.49 times the Sun's mass.[6] It is radiating 158 times the luminosity of the Sun from its enlarged photosphere at an effective temperature of 4,416 K.[2]

The spiral galaxy in Ursa Major, NGC 3877 (= H I.201), type Sc, is best found from Chi Ursae Majoris, which is almost exactly 15 arcminutes north of the galaxy.

References
  1. van Leeuwen, F. (2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, arXiv:0708.1752, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357, S2CID 18759600.
  2. Jennens, P. A.; Helfer, H. L. (September 1975), "A new photometric metal abundance and luminosity calibration for field G and K giants", Monthly Notices of the Royal Astronomical Society, 172 (3): 667–679, Bibcode:1975MNRAS.172..667J, doi:10.1093/mnras/172.3.667.
  3. Alves, David R. (August 2000), "K-Band Calibration of the Red Clump Luminosity", The Astrophysical Journal, 539 (2): 732–741, arXiv:astro-ph/0003329, Bibcode:2000ApJ...539..732A, doi:10.1086/309278, S2CID 16673121.
  4. Keenan, Philip C.; McNeil, Raymond C. (1989), "The Perkins catalog of revised MK types for the cooler stars", Astrophysical Journal Supplement Series, 71: 245, Bibcode:1989ApJS...71..245K, doi:10.1086/191373.
  5. Park, Sunkyung; et al. (2013), "Wilson-Bappu Effect: Extended to Surface Gravity", The Astronomical Journal, 146 (4): 73, arXiv:1307.0592, Bibcode:2013AJ....146...73P, doi:10.1088/0004-6256/146/4/73, S2CID 119187733.
  6. Luck, R. Earle (2015), "Abundances in the Local Region. I. G and K Giants", Astronomical Journal, 150 (3), 88, arXiv:1507.01466, Bibcode:2015AJ....150...88L, doi:10.1088/0004-6256/150/3/88, S2CID 118505114.
  7. Nordgren, Tyler E.; et al. (December 1999), "Stellar Angular Diameters of Late-Type Giants and Supergiants Measured with the Navy Prototype Optical Interferometer", The Astronomical Journal, 118 (6): 3032–3038, Bibcode:1999AJ....118.3032N, doi:10.1086/301114.{{citation}}: CS1 maint: multiple names: authors list (link)
  8. Bakich, Michael E. (1995), The Cambridge Guide to the Constellations, Cambridge University Press, pp. 112, 116, ISBN 0521449219
  9. "chi UMa". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2017-02-22.{{cite web}}: CS1 maint: postscript (link)
  10. "Naming Stars". IAU.org. Retrieved 16 December 2017.
  11. Eggleton, P. P.; Tokovinin, A. A. (September 2008), "A catalogue of multiplicity among bright stellar systems", Monthly Notices of the Royal Astronomical Society, 389 (2): 869–879, arXiv:0806.2878, Bibcode:2008MNRAS.389..869E, doi:10.1111/j.1365-2966.2008.13596.x, S2CID 14878976.
  12. Richard Hinckley Allen: Star Names — Their Lore and Meaning: Ursa Major
  13. "IAU Working Group on Star Names (WGSN)". Retrieved 22 May 2016.
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