Gamma Ursae Minoris

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Gamma Ursae Minoris^[1]

Starmap indicating the location of Gamma Ursae Minoris.
Observation data Epoch J2000.0      Equinox J2000.0
Constellation	Ursa Minor
Right ascension	15h 20m 43.7155s
Declination	+71° 50' 02.458"
Apparent magnitude (V)	+3.027
Characteristics
Spectral type	A3Iab:
U-B color index	+0.12
B-V color index	+0.05
Astrometry
Radial velocity (Rv)	-3.9 km/s
Proper motion (μ)	RA: -18.03 mas/yr Dec.: 17.68 mas/yr
Parallax (π)	6.79 ± 0.46 mas
Distance	480 ± 30 ly (147 ± 10 pc)
Other designations
Pherkad, Pherkad Major, Gamma Ursae Minoris, 13 Ursae Minoris, HR 5735, BD+72°679, HD 137422, SAO 8220, HIP 75097, GC 20692

Gamma Ursae Minoris (γ UMi, γ Ursae Minoris; also 13 UMi) is a slightly variable star in the constellation Ursa Minor. It also has the common name Pherkad. Together with Beta Ursae Minoris, Gamma forms the end of the dipper pan of the "Little Dipper". The name "Pherkad" derives from the Arabic فرقد farqad "calf", short for aḫfa al farkadayn "the dim one of the two calves", Pherkad and Kochab. (The full name Ahfa al Farkadain is now applied to ζ UMi.) γ UMi is sometimes called Pherkad Major to distinguish it from 11 Ursae Minoris Pherkad Minor.

Together, Pherkad and Kochab are also called the "Guardians of the Pole."^[2]

Gamma Ursae Minoris has apparent magnitude +3.00. It is approximately 480 light years from Earth and is of spectral class A3, meaning it has a surface temperature of 7,500 to 11,000 kelvins. It is classified as a Delta Scuti type variable star and its brightness varies by 0.05 magnitudes with a period of 3.43 hours. It is 1100 times more luminous than the Sun, and possesses a radius 15 times that of the Sun.^[2]

[edit] References

1. ^ "Simbad Query Result". Simbad. http://simbad.u-strasbg.fr/simbad/sim-id?protocol=html&Ident=13+UMi&NbIdent=1&Radius=2&Radius.unit=arcmin&submit=submit+id. Retrieved October 5, 2007. 
2. ^ ^{a b} "Pherkad". Simbad. http://www.astro.uiuc.edu/~kaler/sow/pherkad.html. Retrieved October 5, 2007. 

Coordinates: 15^h 20^m 43.7155^s, +71° 50′ 02.458″