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 UMi, δ Ursae Minoris; also 23 UMi) is a star in the constellation Ursa Minor. It has 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 γ UMi and 11 UMi.

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

In science fiction[edit]

The star is mentioned in the Honorverse, a series of military science fiction novels written by David Weber, as the headquarters of Technodyne Industries of Yildun, a major Solarian League shipbuilding corporation with rather questionable ethics (e.g. business ties with Manpower Incorporated and Jessyk Combine, both of Mesa), though the star system is described as including only a (highly mineral-and-metals-rich) asteroid belt.


  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:0708.1752, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357 
  4. ^ Jim Kaler. "The Polar Project". University of Illinois. Retrieved 2012-03-04. 

External links[edit]