Delta Ursae Minoris

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δ Ursae Minoris
Diagram showing star positions and boundaries of the Ursa Minor constellation and its surroundings
Cercle rouge 100%.svg

Location of δ UMi (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Ursa Minor[1]
Right ascension 17h 32m 12.9s[2]
Declination 86° 35′ 11.25″[2]
Apparent magnitude (V) 4.35[2]
Spectral type A1Vn[2]
Radial velocity (Rv) −7.6[2] km/s
Parallax (π) 18.95 ± 0.14[3] mas
Distance 172 ± 1 ly
(52.8 ± 0.4 pc)
Absolute magnitude (MV) 0.62[4]
Radius 2.8[1] R
Luminosity 47[1] L
Temperature 9000[1] K
Rotation 19 hours[1]
Other designations
Yildun, Vildiur, Gildun, Pherkard,
Jildun, 23 Ursae Minoris, HR 6789, HD 166205, BD+86 269, FK5 913, HIP 85822, SAO 2937, GC 24236

Delta Ursae Minoris (δ Ursae Minoris, abbreviated Delta UMi, δ UMi), also named Yildun,[5] is a star in the constellation of Ursa Minor.

Delta Ursae Minoris is a white A-type main sequence dwarf with an apparent magnitude of +4.35 approximately 172 light years from the Sun.[2]


δ Ursae Minoris (Latinised to Delta Ursae Minoris) is the star's Bayer designation.

It bore the traditional name Yildun (also spelled Vildiur, Jildun, Gildun, and Yilduz) from the Turkish yıldız "star". It may also[citation needed] have been called Pherkard, an alternate spelling of Pherkad, used for Gamma Ursae Minoris and 11 Ursae Minoris. In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN)[6] to catalogue and standardize proper names for stars. The WGSN approved the name Yildun for this star on 21 August 2016 and it is now so entered in the IAU Catalog of Star Names.[5]


  1. ^ a b c d e Jim Kaler. "YILDUN (Delta Ursae Minoris)". Retrieved 2012-03-05. 
  2. ^ a b c d e f "Delta Ursae Minoris". SIMBAD Astronomical Database. Retrieved 2012-03-04. 
  3. ^ van Leeuwen, F. (November 2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, arXiv:0708.1752free to read, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357 
  4. ^ Jim Kaler. "The Polar Project". University of Illinois. Retrieved 2012-03-04. 
  5. ^ a b "IAU Catalog of Star Names". Retrieved 28 July 2016. 
  6. ^ IAU Working Group on Star Names (WGSN), International Astronomical Union, retrieved 22 May 2016. 

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