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Created page with "{{Night Sky | image = | designation =γ Ursae Minoris<br/>Pherkad | rightascension =15<sup>h</sup> 20<sup>m</sup> 43.7160<sup>s</sup><ref name=simbad>[https://s..."
{{Night Sky
| image =
| designation =γ Ursae Minoris<br/>Pherkad
| rightascension =15<sup>h</sup> 20<sup>m</sup> 43.7160<sup>s</sup><ref name=simbad>[https://simbad.u-strasbg.fr/simbad/sim-id?Ident=gamma+ursae+minoris&NbIdent=1&Radius=2&Radius.unit=arcmin&submit=submit+id Gamma Ursae Minoris] from the [http://simbad.u-strasbg.fr/simbad SIMBAD Astronomical Database]</ref><ref name=hip>{{cite journal
|last1=van Leeuwen|first1=F.
|title=Validation of the new Hipparcos reduction
|journal=Astronomy & Astrophysics
|volume=474
|issue=2|page=653-664|date=2007
|doi=10.1051/0004-6361:20078357
|bibcode=A&A...474..653V
|ref=harv
}} {{arXiv|0708.1752}}
</ref>
| declination =+71° 50′ 02.4596″<ref name=simbad/><ref name=hip/>
| distance =487 ly<ref name=illinois>{{cite web|url=http://stars.astro.illinois.edu/sow/pherkad.html|title=Pherkad|accessdate=2019-03-26}}</ref>
| constellation =Ursa Minor
| type =Main sequence star
| dimensions =
| magnitude =Apparent Mag: +2.438<ref name=constellation-guide>{{cite web|url=https://www.constellation-guide.com/big-dipper/|title=Big Dipper|accessdate=2019-03-26}}</ref><br/>Absolute Mag: +18.32<ref>From definition of absolute magnitude, using apparent magnitude (+2.438) and distance (487 ly) given here.</ref>
| redshift =
| radvelocity =-3.9±0.6 km/s<ref name=simbad/><ref>{{cite journal
|last1=Gontcharov |first1=G.
|title=Pulkovo Compilation of Radial Velocities for 35 495 Hipparcos stars in a common system
|journal=Astronomy Letters
|volume=32
|issue=11|page=759-771|date=2006
|doi=10.1134/S1063773706110065
|bibcode=2006AstL...32..759G
|ref=harv
}} {{arXiv|1606.08053}}
</ref>
| propmotion =RA: -17.73 mas/yr<ref name=simbad/><ref name=hip/><br/>Dec.: 17.90 mas/yr<ref name=simbad/><ref name=hip/>
| parallax =6.70±0.11 mas<ref name=simbad/><ref name=hip/>
}}
'''Gamma Ursae Minoris''' (γ Ursae Minoris, Gamma UMi, γ UMi) is a [[main sequence star]] in the [[constellation]] of [[Ursa Minor]], the little bear.<ref name=constellation-guide/> The star is sometimes also called "Pherkad", "Phecda" or "Phad" (from the Arabic fakhð ad-dubb, “the thigh of the bear”). Together with the star Beta Ursae Minoris (Kochab), it is one of the Guardians of the Pole.<ref name=earthsky>{{cite web|url=https://earthsky.org/brightest-stars/kochab-and-pherkad-guard-the-north-celestial-pole|title=The Guardians of the Pole|accessdate=2019-03-26}}</ref> With an [[star magnitude|apparent magnitude]] of roughly +2.4 the star is easily visible to the unaided eye and can be observed in the Northern hemisphere with ease.
The third brightest star in [[Ursa Minor]], it it thought to lie approximately 187 [[light year]]s away, though other sources place it much lower at 83.2 ly.<ref name=illinois/><ref name=universeguide>{{cite web|url=https://www.universeguide.com/star/pherkad|title=Pherkad (Gamma Ursae Minoris, 13 Ursae Minoris)|accessdate=2019-03-26}}</ref><ref name=constellation-guide/> It is noticeably larger than the [[Sun]], with around 15 times the solar radius.<ref name=illinois/> With a [[spectral type|spectral class]] of A2III C,<ref name=simbad/> its surface temperature has been estimated to be 8,280 kelvin.<ref name=illinois/> The luminosity of Gamma Ursae Minoris is thought to be 1,050 times greater than that of Sol from this its [[mass (science)|mass]] to be 4.8 [[solar mass]]es. The star rotates rapidly, so that a point on its equator moves at 175 km/s.<ref name=illinois/> Its negative radial [[velocity]] of -3.9±0.6 km/s means it is travelling towards [[Earth]].<ref name=simbad/>
The star is thought to be a delta scuti [[variable star]], though classifying it has proved tricky.<ref name=simbad/> It was originally believed to be a member of the "Maia" class (after a star in the [[Pleiades]]), but the whole class has since disappeared and is no longer used.<ref name=illinois/> Gamma Ursae Minoris has a period of 2.32 hours over which time it varies by around 0.1 magnitudes.<ref>{{cite web|url=http://www.sai.msu.su/gcvs/cgi-bin/ident.cgi?cat=Hip+&num=75097|title=Hip 75097-GCVS Query forms|accessdate=2019-03-26}}</ref><ref>{{cite journal
|last1=Joshi |first1=S.
|last2=Gurtu |first2=S.
|last3=Joshi |first3=M.
|display-authors=3
|title=The light variation of gamma Ursae Minoris
|journal=The Observatory
|volume=89
|page=112-114|date=1969
|bibcode=1969Obs....89..112J
|ref=harv
}}
</ref>
==References==
{{reflist}}
{{Stars}}
[[Category:Astronomy]]
[[Category:Stars]]
| image =
| designation =γ Ursae Minoris<br/>Pherkad
| rightascension =15<sup>h</sup> 20<sup>m</sup> 43.7160<sup>s</sup><ref name=simbad>[https://simbad.u-strasbg.fr/simbad/sim-id?Ident=gamma+ursae+minoris&NbIdent=1&Radius=2&Radius.unit=arcmin&submit=submit+id Gamma Ursae Minoris] from the [http://simbad.u-strasbg.fr/simbad SIMBAD Astronomical Database]</ref><ref name=hip>{{cite journal
|last1=van Leeuwen|first1=F.
|title=Validation of the new Hipparcos reduction
|journal=Astronomy & Astrophysics
|volume=474
|issue=2|page=653-664|date=2007
|doi=10.1051/0004-6361:20078357
|bibcode=A&A...474..653V
|ref=harv
}} {{arXiv|0708.1752}}
</ref>
| declination =+71° 50′ 02.4596″<ref name=simbad/><ref name=hip/>
| distance =487 ly<ref name=illinois>{{cite web|url=http://stars.astro.illinois.edu/sow/pherkad.html|title=Pherkad|accessdate=2019-03-26}}</ref>
| constellation =Ursa Minor
| type =Main sequence star
| dimensions =
| magnitude =Apparent Mag: +2.438<ref name=constellation-guide>{{cite web|url=https://www.constellation-guide.com/big-dipper/|title=Big Dipper|accessdate=2019-03-26}}</ref><br/>Absolute Mag: +18.32<ref>From definition of absolute magnitude, using apparent magnitude (+2.438) and distance (487 ly) given here.</ref>
| redshift =
| radvelocity =-3.9±0.6 km/s<ref name=simbad/><ref>{{cite journal
|last1=Gontcharov |first1=G.
|title=Pulkovo Compilation of Radial Velocities for 35 495 Hipparcos stars in a common system
|journal=Astronomy Letters
|volume=32
|issue=11|page=759-771|date=2006
|doi=10.1134/S1063773706110065
|bibcode=2006AstL...32..759G
|ref=harv
}} {{arXiv|1606.08053}}
</ref>
| propmotion =RA: -17.73 mas/yr<ref name=simbad/><ref name=hip/><br/>Dec.: 17.90 mas/yr<ref name=simbad/><ref name=hip/>
| parallax =6.70±0.11 mas<ref name=simbad/><ref name=hip/>
}}
'''Gamma Ursae Minoris''' (γ Ursae Minoris, Gamma UMi, γ UMi) is a [[main sequence star]] in the [[constellation]] of [[Ursa Minor]], the little bear.<ref name=constellation-guide/> The star is sometimes also called "Pherkad", "Phecda" or "Phad" (from the Arabic fakhð ad-dubb, “the thigh of the bear”). Together with the star Beta Ursae Minoris (Kochab), it is one of the Guardians of the Pole.<ref name=earthsky>{{cite web|url=https://earthsky.org/brightest-stars/kochab-and-pherkad-guard-the-north-celestial-pole|title=The Guardians of the Pole|accessdate=2019-03-26}}</ref> With an [[star magnitude|apparent magnitude]] of roughly +2.4 the star is easily visible to the unaided eye and can be observed in the Northern hemisphere with ease.
The third brightest star in [[Ursa Minor]], it it thought to lie approximately 187 [[light year]]s away, though other sources place it much lower at 83.2 ly.<ref name=illinois/><ref name=universeguide>{{cite web|url=https://www.universeguide.com/star/pherkad|title=Pherkad (Gamma Ursae Minoris, 13 Ursae Minoris)|accessdate=2019-03-26}}</ref><ref name=constellation-guide/> It is noticeably larger than the [[Sun]], with around 15 times the solar radius.<ref name=illinois/> With a [[spectral type|spectral class]] of A2III C,<ref name=simbad/> its surface temperature has been estimated to be 8,280 kelvin.<ref name=illinois/> The luminosity of Gamma Ursae Minoris is thought to be 1,050 times greater than that of Sol from this its [[mass (science)|mass]] to be 4.8 [[solar mass]]es. The star rotates rapidly, so that a point on its equator moves at 175 km/s.<ref name=illinois/> Its negative radial [[velocity]] of -3.9±0.6 km/s means it is travelling towards [[Earth]].<ref name=simbad/>
The star is thought to be a delta scuti [[variable star]], though classifying it has proved tricky.<ref name=simbad/> It was originally believed to be a member of the "Maia" class (after a star in the [[Pleiades]]), but the whole class has since disappeared and is no longer used.<ref name=illinois/> Gamma Ursae Minoris has a period of 2.32 hours over which time it varies by around 0.1 magnitudes.<ref>{{cite web|url=http://www.sai.msu.su/gcvs/cgi-bin/ident.cgi?cat=Hip+&num=75097|title=Hip 75097-GCVS Query forms|accessdate=2019-03-26}}</ref><ref>{{cite journal
|last1=Joshi |first1=S.
|last2=Gurtu |first2=S.
|last3=Joshi |first3=M.
|display-authors=3
|title=The light variation of gamma Ursae Minoris
|journal=The Observatory
|volume=89
|page=112-114|date=1969
|bibcode=1969Obs....89..112J
|ref=harv
}}
</ref>
==References==
{{reflist}}
{{Stars}}
[[Category:Astronomy]]
[[Category:Stars]]