Chi Ursae Majoris

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Chi Ursae Majoris
Diagram showing star positions and boundaries of the Ursa Major constellation and its surroundings
Cercle rouge 100%.svg

Location of χ Ursae Majoris (circled)
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Ursa Major
Right ascension 10h 53m 58.74035s[1]
Declination +43° 11′ 23.8483″[1]
Apparent magnitude (V) 3.72[2]
Spectral type K0.5 IIIb[3]
U−B color index +1.16[2]
B−V color index +1.18[2]
Radial velocity (Rv) −9.02±0.20[2] km/s
Proper motion (μ) RA: +42.97[1] mas/yr
Dec.: −23.62[1] mas/yr
Parallax (π) 13.24 ± 0.50[1] mas
Distance 246 ± 9 ly
(76 ± 3 pc)
Radius 21 R
Luminosity 158 L
Surface gravity (log g) 2.2 cgs
Temperature 4,416±9 K
Metallicity [Fe/H] −0.44 dex
Rotational velocity (v sin i) 2.3 km/s
Other designations
Alkaphrah, El Koprah, χ UMa, 63 UMa, BD+48° 1966, FK5 441, HD 102224, HIP 57399, HR 4518, SAO 43886.[4]
Database references
Chi Ursae Majoris (top) and NGC 3877 (bottom)

Chi Ursae Majoris (Chi UMa, χ Ursae Majoris, χ UMa) is a star in the constellation Ursa Major. It has the traditional names Alkafzah, Alkaphrah, and El Koprah.

Chi Ursae Majoris is an orange K-type giant with an apparent magnitude of +3.69. It is approximately 196 light years from Earth. This star has 20.8 ± 0.8 times the radius of the Sun.[5]

In Chinese astronomy, Alkafzah is called Tai Yang Show, "the Sun Governor".[6] 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 stand alone in Guard of the Sun asterism, Purple Forbidden enclosure (see : Chinese constellation).

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 arc minutes north of the galaxy.

See also[edit]


  1. ^ a b c d e van Leeuwen, F. (2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, arXiv:0708.1752Freely accessible, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357. 
  2. ^ a b c d e 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: 667–679, Bibcode:1975MNRAS.172..667J, doi:10.1093/mnras/172.3.667. 
  3. ^ 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. 
  4. ^ "chi UMa -- High proper-motion Star", SIMBAD Astronomical Database, Centre de Données astronomiques de Strasbourg, retrieved 2017-02-22. 
  5. ^ 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. 
  6. ^ Richard Hinckley Allen: Star Names — Their Lore and Meaning: Ursa Major

External links[edit]