Gamma Ursae Minoris

Gamma Ursae Minoris (γ Ursae Minoris, abbreviated Gamma UMi, γ UMi), also named Pherkad /ˈfɜːrkæd/,[10][11] is a star in the northern circumpolar 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 487 light-years (149 parsecs) from the Sun.[1]

γ Ursae Minoris
Ursa Minor constellation map
Red circle.svg
Location of γ Ursae Minoris (circled)
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Ursa Minor
Right ascension  15h 20m 43.71604s[1]
Declination +71° 50′ 02.4596″[1]
Apparent magnitude (V) +3.05[2]
Characteristics
Spectral type A2 III[3]
U−B color index +0.08[2]
B−V color index +0.09[2]
Astrometry
Radial velocity (Rv)−3.9[4] km/s
Proper motion (μ) RA: −17.73[1] mas/yr
Dec.: +17.90[1] mas/yr
Parallax (π)6.70 ± 0.11[1] mas
Distance487 ± 8 ly
(149 ± 2 pc)
Absolute magnitude (MV)–2.84[5]
Details
Radius15[6] R
Luminosity1,100[6] L
Surface gravity (log g)2.53[7] cgs
Temperature8,280[8] K
Rotational velocity (v sin i)180[9] km/s
Other designations
Pherkad, Pherkad Major, Gamma Ursae Minoris, 13 Ursae Minoris, HR 5735, BD+72°679, HD 137422, SAO 8220, HIP 75097
Database references
SIMBADdata

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.[12]

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 organized a Working Group on Star Names (WGSN)[13] 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.[11]

In Chinese, 北極 (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.[14] Consequently, the Chinese name for Gamma Ursae Minoris itself is 北極一 (Běi Jí yī, English: the First Star of North Pole), representing 太子 (Tàizǐ), meaning Crown Prince.[15]

Properties

Gamma Ursae Minoris has apparent magnitude +3.05[2] and can be readily observed with the naked eye even in a city-lit night sky. It has an absolute magnitude of –2.84.[5] Measurement of the star's spectrum resulted in a stellar classification of A3 Iab, with the luminosity class of 'Iab' indicating this is an intermediate luminosity supergiant star. The effective temperature of the star's outer envelope is 8,280 K,[8] giving it the typical white hue of an A-type star.[16] It is rotating rapidly, with the projected rotational velocity of 180 km s−1[9] 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.[7] It is 1100 times more luminous than the Sun, and possesses a radius 15 times that of the Sun.[6]

Pherkad in fiction

Pherkad (spelled as Pherkard) also features in Cthulhu Mythos, in the short story "The Thing in the Library", by Crispin Burnham and E.P. Berglund. It is mentioned as the stellar abode of the flaming Outer God Yomagn'tho.[17]

References

  1. ^ a b c d e f van Leeuwen, F. (November 2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, arXiv:0708.1752, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357
  2. ^ a b c d Fernie, J. D. (May 1983), "New UBVRI photometry for 900 supergiants", Astrophysical Journal Supplement Series, 52: 7–22, Bibcode:1983ApJS...52....7F, doi:10.1086/190856
  3. ^ Abt, Helmut A.; Morrell, Nidia I. (1995). "The Relation between Rotational Velocities and Spectral Peculiarities among A-Type Stars". Astrophysical Journal Supplement Series. 99: 135. Bibcode:1995ApJS...99..135A. doi:10.1086/192182.
  4. ^ Wielen, R.; et al. (1999), "Sixth Catalogue of Fundamental Stars (FK6). Part I. Basic fundamental stars with direct solutions", Veröff. Astron. Rechen-Inst. Heidelb, Veröffentlichungen des Astronomisches Rechen-Institut Heidelberg, 35, Bibcode:1999VeARI..35....1W
  5. ^ a b Verdugo, E.; et al. (November 2005). "Do A-type Supergiants have Magnetic Fields?". In Ignace, Richard; Gayley, Kenneth G. (eds.). The Nature and Evolution of Disks Around Hot Stars; Proceedings of a meeting held 7-9 July 2004 in Johnson City, Tennessee, USA. The Nature and Evolution of Disks Around Hot Stars. ASP Conference Series. 337. p. 324. Bibcode:2005ASPC..337..324V.
  6. ^ a b c Kaler, James B., "Pherkad (Gamma Ursae Minoris)", Stars, University of Illinois, retrieved 2007-10-05
  7. ^ a b Hauck, B.; Jaschek, C. (February 2000), "A-shell stars in the Geneva system", Astronomy and Astrophysics, 354: 157–162, Bibcode:2000A&A...354..157H
  8. ^ a b Zorec, J.; et al. (July 2009), "Fundamental parameters of B supergiants from the BCD system. I. Calibration of the (λ_1, D) parameters into Teff", Astronomy and Astrophysics, 501 (1): 297–320, arXiv:0903.5134, Bibcode:2009A&A...501..297Z, doi:10.1051/0004-6361/200811147
  9. ^ a b Royer, F.; et al. (October 2002), "Rotational velocities of A-type stars in the northern hemisphere. II. Measurement of v sin i", Astronomy and Astrophysics, 393 (3): 897–911, arXiv:astro-ph/0205255, Bibcode:2002A&A...393..897R, doi:10.1051/0004-6361:20020943
  10. ^ Rumrill, H. B. (June 1936). "Star Name Pronunciation". Publications of the Astronomical Society of the Pacific. San Francisco, California. 48 (283).
  11. ^ a b "Naming Stars". IAU.org. Retrieved 4 March 2018.
  12. ^ Kostjuk, N. D. (2004). "VizieR Online Data Catalog: HD-DM-GC-HR-HIP-Bayer-Flamsteed Cross Index (Kostjuk, 2002)". VizieR On-line Data Catalog: IV/27A. Originally published in: Institute of Astronomy of Russian Academy of Sciences (2002). 4027. Bibcode:2004yCat.4027....0K.
  13. ^ IAU Working Group on Star Names (WGSN), International Astronomical Union, retrieved 22 May 2016.
  14. ^ ‹See Tfd›(in Chinese) 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.
  15. ^ ‹See Tfd›(in Chinese) 香港太空館 - 研究資源 - 亮星中英對照表 Archived August 10, 2010, at the Wayback Machine, Hong Kong Space Museum. Accessed on line November 23, 2010.
  16. ^ "The Colour of Stars", Australia Telescope, Outreach and Education, Commonwealth Scientific and Industrial Research Organisation, December 21, 2004, archived from the original on 2012-03-18, retrieved 2012-01-16
  17. ^ Crispin Burnham & E.P. Berglund. "The Thing in the Library". Archived from the original on 2005-03-22. Retrieved 2013-01-28.
Preceded by
Thuban
Pole Star
1900–500 BCE]]
Succeeded by
Polaris

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

Beta Ursae Minoris

Beta Ursae Minoris (β Ursae Minoris, abbreviated Beta UMi, β UMi), formally named Kochab , is the brightest star in the bowl of the Little Dipper asterism (which is part of the constellation of Ursa Minor), and only slightly fainter than Polaris, the northern pole star and brightest star in Ursa Minor. Kochab is 16 degrees from Polaris and has an apparent visual magnitude of 2.08. The distance to this star from the Sun can be deduced from the parallax measurements made during the Hipparcos mission, yielding a value of 130.9 light-years (40.1 parsecs).Amateur astronomers can use Kochab as a very precise guide for setting up a telescope, as the celestial north pole is located 43 arcminutes away from Polaris, very close to the line connecting Polaris with Kochab.

Extraterrestrial places in the Cthulhu Mythos

The following fictional celestial bodies figure prominently in the Cthulhu Mythos stories of H. P. Lovecraft and other writers. Many of these astronomical bodies have parallels in the real universe, but are often renamed in the mythos and given fictitious characteristics. In addition to the celestial places created by Lovecraft, the mythos draws from a number of other sources, including the works of August Derleth, Ramsey Campbell, Lin Carter, Brian Lumley, and Clark Ashton Smith.

Overview:

Name. The name of the celestial body appears first.

Description. A brief description follows.

List of Arabic star names

This is a list of Arabic star names. In Western astronomy, most of the accepted star names are Arabic, a few are Greek and some are of unknown origin. Typically only bright stars have names.

Maia (star)

Maia , designated 20 Tauri (abbreviated 20 Tau), is a star in the constellation of Taurus. It is the fourth-brightest star in the Pleiades open star cluster (M45), after Alcyone, Atlas and Electra, in that order. Maia is a blue giant of spectral type B8 III, and a mercury-manganese star.

Maia's visual magnitude is 3.871, requiring darker skies to be seen. Its total bolometric luminosity is 660 times solar, mostly in the ultraviolet, thus suggesting a radius that is 5.5 times that of the Sun and a mass that is slightly more than 4 times solar. It was thought to be a variable star by astronomer Otto Struve. A class of stars known as Maia variables was proposed, which included Gamma Ursae Minoris, but Maia and some others in the class have since been found to be stable.Maia is surrounded by the Maia Nebula (also known as NGC 1432), one of the brightest patches of nebulosity within the Pleiades star cluster.

Northern Pole

Northern Pole (北极 in Simplified Chinese, běi jí in Pinyin) is a traditional Chinese asterism found in the Purple Forbidden enclosure (紫微垣 in Simplified Chinese, zǐ wēi yuán in Pinyin). It consists of five stars found in the modern constellations of Ursa Minor and Camelopardalis and represents the five stars of the North Pole. During the Qing dynasty, a total of four stars from the constellation Ursa Minor was added to the asterism.

Otto Struve

Not to be confused with his grandfather Otto Wilhelm von Struve (1819–1905)Otto Struve (August 12, 1897 – April 6, 1963) was a Russian-American astronomer. In Russian, his name is sometimes given as Otto Lyudvigovich Struve (Отто Людвигович Струве); however, he spent most of his life and his entire scientific career in the United States. Otto was the descendant of famous astronomers of the Struve family; he was the son of Ludwig Struve, grandson of Otto Wilhelm von Struve and great-grandson of Friedrich Georg Wilhelm von Struve. He was also the nephew of Karl Hermann Struve.With more than 900 journal articles and books, Struve was one of the most distinguished and prolific astronomers of the mid-20th century. He served as director of Yerkes, McDonald, Leuschner and National Radio Astronomy Observatories and is credited with raising worldwide prestige and building schools of talented scientists at Yerkes and McDonald observatories. In particular, he hired Subrahmanyan Chandrasekhar and Gerhard Herzberg who later became Nobel Prize winners. Struve's research was mostly focused on binary and variable stars, stellar rotation and interstellar matter. He was one of the few eminent astronomers in the pre-Space Age era to publicly express a belief that extraterrestrial intelligence was abundant, and so was an early advocate of the search for extraterrestrial life.

Ursa Minor

Ursa Minor (Latin: "Lesser Bear", contrasting with Ursa Major), also known as the Little Bear, is a constellation in the Northern Sky. Like the Great Bear, the tail of the Little Bear may also be seen as the handle of a ladle, hence the North American name, Little Dipper: seven stars with four in its bowl like its partner the Big Dipper. It was one of the 48 constellations listed by the 2nd-century astronomer Ptolemy, and remains one of the 88 modern constellations. Ursa Minor has traditionally been important for navigation, particularly by mariners, because of Polaris being the North Star.

Polaris, the brightest star in the constellation, is a yellow-white supergiant and the brightest Cepheid variable star in the night sky, ranging from an apparent magnitude of 1.97 to 2.00. Beta Ursae Minoris, also known as Kochab, is an aging star that has swollen and cooled to become an orange giant with an apparent magnitude of 2.08, only slightly fainter than Polaris. Kochab and magnitude 3 Gamma Ursae Minoris have been called the "guardians of the pole star". Planets have been detected orbiting four of the stars, including Kochab. The constellation also contains an isolated neutron star—Calvera—and H1504+65, the hottest white dwarf yet discovered, with a surface temperature of 200,000 K.

Stars of Ursa Minor
Bayer
Flamsteed
Variable
HR
HD
Other

Languages

This page is based on a Wikipedia article written by authors (here).
Text is available under the CC BY-SA 3.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.