Gamma Ursae Minoris (γ Ursae Minoris, abbreviated Gamma UMi, γ UMi), also named Pherkad , is a

star A star is an astronomical object comprising a luminous spheroid of plasma held together by its gravity. The nearest star to Earth is the Sun. Many other stars are visible to the naked eye at night, but their immense distances from Earth make ...

in the northern constellation of

Ursa Minor Ursa Minor (Latin: 'Lesser Bear', contrasting with Ursa Major), also known as the Little Bear, is a constellation located in the far northern celestial hemisphere, northern sky. As with the Great Bear, the tail of the Little Bear may also be see ...

. Together with Beta Ursae Minoris (Kochab), it forms the end of the dipper pan of the "Little Dipper", which is an asterism forming the tail of the bear. Based upon

parallax Parallax is a displacement or difference in the apparent position of an object viewed along two different lines of sight and is measured by the angle or semi-angle of inclination between those two lines. Due to foreshortening, nearby object ...

measurements obtained during the

Hipparcos ''Hipparcos'' was a scientific satellite of the European Space Agency (ESA), launched in 1989 and operated until 1993. It was the first space experiment devoted to precision astrometry, the accurate measurement of the positions of celestial obj ...

mission, it is approximately from the Sun.

Nomenclature

''γ Ursae Minoris'' ( Latinised to ''Gamma Ursae Minoris'') is the star's

Bayer designation A Bayer designation is a stellar designation in which a specific star is identified by a Greek or Latin letter followed by the genitive form of its parent constellation's Latin name. The original list of Bayer designations contained 1,564 stars. T ...

. The fainter 11 Ursae Minoris has been called ''γ¹ Ursae Minoris'', in which case ''Gamma Ursae Minoris'' would be designated ''γ²''. However this usage is rarely seen. Gamma Ursae Minoris bore the traditional name ''Pherkad'', which derived from the Arabic فرقد ''farqad'' "calf", short for ''aḫfa al farkadayn'' "the dim one of the two calves", that is Pherkad and Kochab (the full name Ahfa al Farkadain is traditionally applied to Zeta Ursae Minoris). Gamma Ursae Minoris was mostly called ''Pherkad Major'' to distinguish it from ''Pherkad Minor'' (11 Ursae Minoris). In 2016, the

International Astronomical Union The International Astronomical Union (IAU; french: link=yes, Union astronomique internationale, UAI) is a nongovernmental organisation with the objective of advancing astronomy in all aspects, including promoting astronomical research, outreach ...

organized a

Working Group on Star Names The International Astronomical Union (IAU) established a Working Group on Star Names (WGSN) in May 2016 to catalog and standardize List of proper names of stars, proper names for stars for the international astronomical community. It operates under ...

(WGSN) to catalogue and standardize proper names for stars. The WGSN approved the name ''Pherkad'' for Gamma Ursae Minoris on 21 August 2016 and it is now so included in the List of IAU-approved Star Names. In Chinese, (), meaning ''

North Pole The North Pole, also known as the Geographic North Pole or Terrestrial North Pole, is the point in the Northern Hemisphere where the Earth's rotation, Earth's axis of rotation meets its surface. It is called the True North Pole to distingu ...

'', refers to an asterism consisting of Gamma Ursae Minoris, Beta Ursae Minoris,

5 Ursae Minoris 5 Ursae Minoris is a star in the circumpolar constellation of Ursa Minor. It is a faint star but visible to the naked eye with an apparent visual magnitude of 4.253. The distance to this star, as determined from an annual parallax shift o ...

4 Ursae Minoris 4 Ursae Minoris is a binary star system in the northern circumpolar constellation Ursa Minor. It is faintly visible to the naked eye with an apparent visual magnitude of 4.80. Based upon an annual parallax shift of as seen from Earth's ...

and

Σ 1694 Struve 1694 (Σ 1694, Struve 1694) is a double star in the constellation Camelopardalis. Σ 1694 is a double star, with components of magnitudes 5.3m and 5.9m: *Σ 1694A (HD 112028) is a white A-type giant star with an apparent magnitude of 5. ...

. Consequently, the

Chinese name Chinese names or Chinese personal names are names used by individuals from Greater China and other parts of the Chinese-speaking world throughout East and Southeast Asia (ESEA). In addition, many names used in Japan, Korea and Vietnam are oft ...

for Gamma Ursae Minoris itself is (, en, the First Star of North Pole), representing (), meaning ''Crown Prince''.香港太空館 - 研究資源 - 亮星中英對照表
, Hong Kong Space Museum. Accessed on line November 23, 2010.

Properties

Gamma Ursae Minoris has

apparent magnitude Apparent magnitude () is a measure of the brightness of a star or other astronomical object observed from Earth. An object's apparent magnitude depends on its intrinsic luminosity, its distance from Earth, and any extinction of the object's li ...

+3.05 and can be readily observed with the naked eye even in a city-lit night sky. It has an

absolute magnitude Absolute magnitude () is a measure of the luminosity of a celestial object on an inverse logarithmic astronomical magnitude scale. An object's absolute magnitude is defined to be equal to the apparent magnitude that the object would have if it we ...

of –2.84. Measurement of the star's

spectrum A spectrum (plural ''spectra'' or ''spectrums'') is a condition that is not limited to a specific set of values but can vary, without gaps, across a continuum. The word was first used scientifically in optics to describe the rainbow of color ...

resulted in a

stellar classification In astronomy, stellar classification is the classification of stars based on their spectral characteristics. Electromagnetic radiation from the star is analyzed by splitting it with a prism or diffraction grating into a spectrum exhibiting t ...

of A3 Iab, with the

luminosity class In astronomy, stellar classification is the classification of stars based on their spectral characteristics. Electromagnetic radiation from the star is analyzed by splitting it with a prism or diffraction grating into a spectrum exhibiting th ...

of 'Iab' indicating this is an intermediate luminosity

supergiant Supergiants are among the most massive and most luminous stars. Supergiant stars occupy the top region of the Hertzsprung–Russell diagram with absolute visual magnitudes between about −3 and −8. The temperature range of supergiant stars s ...

star. The

effective temperature The effective temperature of a body such as a star or planet is the temperature of a black body that would emit the same total amount of electromagnetic radiation. Effective temperature is often used as an estimate of a body's surface temperature ...

of the star's outer envelope is 8,280 K, giving it the typical white hue of an A-type star. It is rotating rapidly, with the

projected rotational velocity Stellar rotation is the angular motion of a star about its axis. The rate of rotation can be measured from the spectrum of the star, or by timing the movements of active features on the surface. The rotation of a star produces an equatorial bulge ...

of providing a lower limit on the

azimuth An azimuth (; from ar, اَلسُّمُوت, as-sumūt, the directions) is an angular measurement in a spherical coordinate system. More specifically, it is the horizontal angle from a cardinal direction, most commonly north. Mathematicall ...

al velocity along the star's equator. This is classified as a shell star that has a circumstellar disk of gas around the star's equator, which may be causing it to vary in magnitude. It is 1100 times more luminous than the Sun, and possesses a radius 15 times that of the Sun.

Pherkad in fiction

Pherkad (spelled as ''Pherkard'') features in

Cthulhu Mythos The Cthulhu Mythos is a mythopoeia and a shared fictional universe, originating in the works of American horror writer H. P. Lovecraft. The term was coined by August Derleth, a contemporary correspondent and protégé of Lovecraft, to identify ...

References

{{DEFAULTSORT:Gamma Ursae Minoris Ursa Minor (constellation) Ursae Minoris, Gamma Delta Scuti variables A-type giants Pherkad Ursae Minoris, 13 075097 5735 137422 Durchmusterung objects Northern pole stars