Zeta Ursae Minoris
Epoch J2000 Equinox J2000
|Right ascension||15h 44m 03.5193s|
|Declination||+77° 47′ 40.175″|
|Apparent magnitude (V)||+4.32|
|U−B color index||+0.05|
|B−V color index||+0.04|
|Radial velocity (Rv)||–13.1 km/s|
|Proper motion (μ)||RA: 20.07 mas/yr
Dec.: –2.50 mas/yr
|Parallax (π)||8.68 ± 0.47 mas|
|Distance||380 ± 20 ly
(115 ± 6 pc)
Zeta Ursae Minoris (ζ UMi, ζ Ursae Minoris) is a star in the constellation Ursa Minor. It has the traditional name Akhfa al Farkadain, from the Arabic أخفى الفرقدين aḫfa al-farqadayn "the dimmer of the two calves", as opposed to Anwar al Farkadain (η UMi) "the brighter of the two calves". These names were originally applied to Pherkad and Kochab, respectively, the other two stars in the rectangle of Ursa Minor.
Despite its classification as a main sequence dwarf star, Zeta UMi is 3.4 times the mass of the sun and its luminosity is about 200 solar luminosities. At a surface temperature of 8,700 kelvins, this star is actually on the verge of becoming a giant star. Zeta UMi may also be a variable of the Delta Scuti type.
- Perryman, M. A. C.; et al. (1997), "The Hipparcos Catalogue", Astronomy & Astrophysics, 323: L49–L52, Bibcode:1997A&A...323L..49P
- Johnson, H. L.; et al. (1966). "UBVRIJKL photometry of the bright stars". Communications of the Lunar and Planetary Laboratory. 4 (99). Bibcode:1966CoLPL...4...99J.
- Cowley, A.; Cowley, C.; Jaschek, M.; Jaschek, C. (April 1969). "A study of the bright A stars. I. A catalogue of spectral classifications". Astronomical Journal. 74: 375–406. Bibcode:1969AJ.....74..375C. doi:10.1086/110819.
- Evans, D. S. (June 20–24, 1966). "The Revision of the General Catalogue of Radial Velocities". In Batten, Alan Henry; Heard, John Frederick. Determination of Radial Velocities and their Applications, Proceedings from IAU Symposium no. 30. University of Toronto: International Astronomical Union. Bibcode:1967IAUS...30...57E. Retrieved 2009-09-10.
- "NSV 7263 – Variable Star". SIMBAD. Centre de Données astronomiques de Strasbourg. Retrieved 2009-10-28.
- Arabic Star Names Archived February 15, 2009, at the Wayback Machine.
- "Zeta Ursae Minoris - Variable Star". SIMBAD Astronomical Database. Centre de Données astronomiques de Strasbourg. Retrieved 21 June 2014.
- Kaler, James B. "Alifa al Farkadain". Stars. University of Illinois. Retrieved 21 June 2014.