Gamma Ursae Minoris

{{Starbox begin

| name = γ Ursae Minoris

}}

{{Starbox image

| image=

{{Location mark

|image=Ursa Minor constellation map.svg|alt=|float=center|width=240

|label=|position=right

|mark=Red circle.svg|mark_width=10|mark_link=γ UMi

|x=440|y=718

}}

|caption=Location of γ Ursae Minoris (circled)

}}

{{Starbox observe

| epoch = J2000.0

| constell = Ursa Minor

| ra = {{RA|15|20|43.71604}}

| dec = {{DEC|+71|50|02.4596}}

| appmag_v = +3.05

}}

{{Starbox character

| class = A2 III{{cite journal|bibcode=1995ApJS...99..135A|title=The Relation between Rotational Velocities and Spectral Peculiarities among A-Type Stars|journal=Astrophysical Journal Supplement Series |volume=99|pages=135|last1=Abt|first1=Helmut A.|last2=Morrell|first2=Nidia I.|year=1995|doi=10.1086/192182|doi-access=free}}

| b-v = +0.09

| u-b = +0.08

| variable = δ Sct

}}

{{Starbox astrometry

| radial_v = −3.9

| prop_mo_ra = −17.73

| prop_mo_dec = +17.90

| parallax = 6.70

| p_error = 0.11

| parallax_footnote =

| absmag_v = –2.84

}}

{{Starbox detail

| mass =

| radius = 15

| gravity = 2.53

| luminosity = 1,100

| luminosity_bolometric =

| luminosity_visual =

| temperature = 8,280

| metal =

| rotation =

| rotational_velocity = 180

| age =

| age_gyr =

}}

{{Starbox catalog

| names=Pherkad, Pherkad Major, Gamma Ursae Minoris, 13 Ursae Minoris, HR 5735, BD+72°679, HD 137422, SAO 8220, HIP 75097

}}

{{Starbox reference

|Simbad=Gamma+UMi

}}

Gamma Ursae Minoris (γ Ursae Minoris, abbreviated Gamma UMi, γ UMi), also named Pherkad {{IPAc-en|'|f|3r|k|æ|d}},{{cite journal

|title=Star Name Pronunciation

|last=Rumrill |first=H. B.

|journal=Publications of the Astronomical Society of the Pacific

|volume=48

|number=283

|date=June 1936

|page=139 |location = San Francisco, California

|doi=10.1086/124681

|bibcode=1936PASP...48..139R |s2cid=120743052 |doi-access=free

}}{{cite web | url=https://www.iau.org/public/themes/naming_stars/ | title=Naming Stars |publisher=IAU.org |access-date=4 March 2018}} is a star in the northern constellation of Ursa Minor. 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 measurements obtained during the Hipparcos mission, it is approximately {{Convert|487|ly|pc|abbr=off|lk=on}} from the Sun.

Nomenclature

γ Ursae Minoris (Latinised to Gamma Ursae Minoris) is the star's Bayer designation. 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.{{cite journal|bibcode=2004yCat.4027....0K|title=VizieR Online Data Catalog: HD-DM-GC-HR-HIP-Bayer-Flamsteed Cross Index (Kostjuk, 2002)|journal=VizieR On-line Data Catalog: IV/27A. Originally Published in: Institute of Astronomy of Russian Academy of Sciences (2002)|volume=4027|last1=Kostjuk|first1=N. D.|year=2004}}

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).{{citation needed|date=May 2017}} Gamma Ursae Minoris was mostly called Pherkad Major to distinguish it from Pherkad Minor (11 Ursae Minoris). In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN){{citation

| url=https://www.iau.org/science/scientific_bodies/working_groups/280/

| title=IAU Working Group on Star Names (WGSN)

| publisher=International Astronomical Union

| access-date=22 May 2016 | postscript=. }} 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, {{lang|zh|北極}} ({{lang|zh-Latn|Běi Jí}}), meaning North Pole, refers to an asterism consisting of Gamma Ursae Minoris, Beta Ursae Minoris, 5 Ursae Minoris, 4 Ursae Minoris and Σ 1694.{{in lang|zh}} 中國星座神話, written by 陳久金. Published by 台灣書房出版有限公司, 2005, {{ISBN|978-986-7332-25-7}}. Consequently, the Chinese name for Gamma Ursae Minoris itself is {{lang|zh|北極一}} ({{lang|zh-Latn|Běi Jí yī}}, {{langx|en|the First Star of North Pole}}), representing {{lang|zh|太子}} ({{lang|zh-Latn|Tàizǐ}}), meaning Crown Prince.{{in lang|zh}} [http://www.lcsd.gov.hk/CE/Museum/Space/Research/StarName/e_research_chinengstarzone_b.htm#PrupleForbiddenEnclosure 香港太空館 - 研究資源 - 亮星中英對照表] {{webarchive |url=https://web.archive.org/web/20100810114313/http://www.lcsd.gov.hk/CE/Museum/Space/Research/StarName/e_research_chinengstarzone_b.htm#PrupleForbiddenEnclosure |date=August 10, 2010 }}, Hong Kong Space Museum. Accessed on line November 23, 2010.

Properties

Gamma Ursae Minoris has apparent magnitude +3.05 and can be readily observed with the naked eye even in a city-lit night sky. It has an absolute magnitude of –2.84. Measurement of the star's spectrum resulted in a stellar classification of A2 III, with the luminosity class of 'III' indicating this is an expanding giant star that left the main sequence after exhausting its core supply of hydrogen. Based on stellar evolutionary theory, Pherkad might become a Cepheid variable before settling as a red giant similar to its neighbor Kochab, before becoming a white dwarf of roughly 0.85 solar masses. The effective 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 of {{nowrap|180 km s⁻¹}} providing a lower limit on the azimuthal 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.

References

{{Reflist|30em|refs=

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{{citation | first=F. | last=van Leeuwen |date=November 2007 | title=Validation of the new Hipparcos reduction | journal=Astronomy and Astrophysics | volume=474 | issue=2 | pages=653–664 | bibcode=2007A&A...474..653V | doi=10.1051/0004-6361:20078357 |arxiv = 0708.1752 | s2cid=18759600 }}

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{{citation | last1=Fernie | first1=J. D. | title=New UBVRI photometry for 900 supergiants | journal=Astrophysical Journal Supplement Series | volume=52 | pages=7–22 |date=May 1983 | doi=10.1086/190856 | bibcode=1983ApJS...52....7F | doi-access=free }}

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{{cite conference | display-authors=1 | last1=Verdugo | first1=E. | last2=Henrichs | first2=H. F. | last3=Talavera | first3=A. | last4=Gómez de Castro | first4=A. I. | last5=Schnerr | first5=R. S. | last6=Geers | first6=V. C. | contribution=Do A-type Supergiants have Magnetic Fields? | title=The Nature and Evolution of Disks Around Hot Stars; Proceedings of a meeting held 7-9 July 2004 in Johnson City, Tennessee, USA | journal=The Nature and Evolution of Disks Around Hot Stars | series=ASP Conference Series | volume=337 | editor1-first=Richard | editor1-last=Ignace | editor2-first=Kenneth G. | editor2-last=Gayley | page=324 |date=November 2005 | bibcode=2005ASPC..337..324V }}

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{{citation | first1=James B. | last1=Kaler | title=Pherkad (Gamma Ursae Minoris) | work=Stars | publisher=University of Illinois | url=http://stars.astro.illinois.edu/sow/pherkad.html | access-date=2007-10-05 }}

{{citation |title=The Colour of Stars |date=December 21, 2004 |work=Australia Telescope, Outreach and Education |publisher=Commonwealth Scientific and Industrial Research Organisation |url=http://outreach.atnf.csiro.au/education/senior/astrophysics/photometry_colour.html |access-date=2012-01-16 |url-status=dead |archive-url=https://web.archive.org/web/20120318151427/http://outreach.atnf.csiro.au/education/senior/astrophysics/photometry_colour.html |archive-date=2012-03-18 }}

}}

Category:Ursa Minor

Ursae Minoris, Gamma

Category:Delta Scuti variables

Category:A-type giants

Category:Durchmusterung objects

Category:Northern pole stars