Alpha Cephei: Difference between revisions
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{{Short description|Star in the constellation of Cepheus}} |
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{{Hatnote|"Alderamin" redirects here. It is not to be confused with [[Aldebaran]] or [[Alderaan]].}} |
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{{Starbox begin |
{{Starbox begin |
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| name= |
| name=α Cephei |
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}} |
}} |
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{{Starbox image |
{{Starbox image |
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| image |
| image= |
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{{Location mark |
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<div style="position: relative">[[File:Cepheus IAU.svg|250px|alt=Diagram showing star positions and boundaries of the Cepheus constellation and its surroundings]] |
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|image=Cepheus constellation map.svg|alt=|float=center|width=240 |
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<div style="position: absolute; left: 63.0%; top: 60.2%;">[[File:Cercle rouge 100%.svg|12px]]</div> |
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|label=|position=right |
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</div> |
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|mark=Red circle.svg|mark_width=10|mark_link=α Cep |
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| caption=Location of α Cephei (circled) |
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|x=814|y=886 |
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}} |
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|caption=Location of α Cephei (circled) |
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}} |
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{{Starbox observe |
{{Starbox observe |
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| ra={{RA|21|18|34.7715}}<ref name="SIMBAD"/> |
| ra={{RA|21|18|34.7715}}<ref name="SIMBAD"/> |
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| dec={{DEC|+62|35|08.061}}<ref name="SIMBAD"/> |
| dec={{DEC|+62|35|08.061}}<ref name="SIMBAD"/> |
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| appmag_v=2. |
| appmag_v=2.46<ref name=AAVSO/> |
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| constell=[[Cepheus (constellation)|Cepheus]] |
| constell=[[Cepheus (constellation)|Cepheus]] |
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}} |
}} |
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{{Starbox character |
{{Starbox character |
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| class=A8Vn |
| class=A8Vn<ref name=gray/> or A7IV-V<ref name=vanBelle2006/> |
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| b-v=+0.21<ref name="MERMILLIOD"/> |
| b-v=+0.21<ref name="MERMILLIOD"/> |
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| u-b=+0.12<ref name="MERMILLIOD"/> |
| u-b=+0.12<ref name="MERMILLIOD"/> |
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| variable=Delta Scuti |
| variable=suspected [[Delta Scuti|δ Sct]]<ref name=gcvs/> |
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}} |
}} |
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{{Starbox astrometry |
{{Starbox astrometry |
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{{Starbox detail |
{{Starbox detail |
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| source=<ref name=vanBelle2006/> |
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| mass={{val|2.00|0.15}} |
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| radius=2.3<ref name=aass85_3_1015/> |
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| radius={{val|2.175|0.046}} (polar)<br>{{val|2.823|0.097}} (equator) |
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| luminosity=17<ref name=aass85_3_1015/> |
| luminosity=17<ref name=aass85_3_1015/> |
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| gravity=3.99<ref name=aass85_3_1015/> |
| gravity=3.99<ref name=aass85_3_1015/> |
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| temperature={{val|8440|430|700|fmt=commas}} (polar)<br>{{val|7600|fmt=commas}} (equator) |
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| temperature=7,740 ± 170<ref name=aass85_3_1015/> |
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| metal_fe= |
| metal_fe=0.09 |
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| rotational_velocity= |
| rotational_velocity={{val|283|19}} |
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| rotation={{val|12.11|0.26|u=hours}} |
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| age= |
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| age_myr=820 |
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}} |
}} |
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{{Starbox catalog |
{{Starbox catalog |
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| names={{odlist | name=Alderamin | B=α Cep | F=5 Cep | V= | BD=+61°2111 | FK5=803 | GJ=826 | HD=203280 | HIP=105199 | HR=8162 | SAO=19302 | AG=+62° 1226 | 2MASS=J21183475+6235081 | CCDM=J21186+6236A | GCTP=5139.00 }}<ref name=SIMBAD/> |
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| names=Alderamin, [[Flamsteed designation|5 Cep]], [[2MASS]] J21183475+6235081, [[Astronomische Gesellschaft Katalog|AG]]+62° 1226, [[Bonner Durchmusterung|BD]] +61°2111, [[Catalog of Components of Double and Multiple Stars|CCDM]] J21186+6236A, [[Catalogues of Fundamental Stars|FK5]] 803, [[General Catalogue of Trigonometric Parallaxes|GCTP]] 5139.00, [[Henry L. Giclas catalogue|Gl]] 826, [[Henry Draper catalogue|HD]] 203280, [[Hipparcos catalogue|HIP]] 105199, [[Harvard Revised catalogue|HR]] 8162, [[Smithsonian Astrophysical Observatory Star Catalog|SAO]] 19302. |
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}} |
}} |
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{{Starbox reference |
{{Starbox reference |
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{{Starbox end}} |
{{Starbox end}} |
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'''Alpha Cephei''' (α Cep, α |
'''Alpha Cephei''' ('''α Cephei''', abbreviated '''Alpha Cep''', '''α Cep'''), officially named '''Alderamin''' {{IPAc-en|æ|l|'|d|Er|@|m|I|n}},<ref name=Kunitzsch/><ref name="IAU-CSN"/> is a [[second magnitude star]] in the [[constellation]] of [[Cepheus (constellation)|Cepheus]] near the [[Celestial pole|northern pole]]. The star is relatively close to [[Earth]] at 49 [[light year]]s (''ly'') and drifting closer with a heliocentric [[radial velocity]] of about −16 km/s. |
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== |
==Nomenclature== |
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With a declination in excess of 62 degrees north, Alderamin is mostly visible to observers in the northern hemisphere, though the star is still visible to latitudes as far south as -27°, albeit just above the horizon. The star is [[Circumpolar star|circumpolar]] throughout all of [[Europe]], northern Asia, Canada, and American cities as far south as [[San Diego]]. Since Alderamin has an apparent magnitude of about 2.5, the star is easily observable to the naked eye, even in [[light pollution|light-polluted]] cities. |
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''α Cephei'' ([[Latinisation of names|Latinised]] to ''Alpha Cephei'') is the star's [[Bayer designation]]. It has a [[Flamsteed designation]] of 5 Cephei. |
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== Properties == |
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Alderamin is a white [[Spectral classification#Class A|Class A]] star, evolving off the [[main sequence]] into a [[subgiant]], probably on its way to becoming a [[red giant]] as its hydrogen supply runs low. In 2007, the star's apparent magnitude was recalibrated at 2.5141 along with an updated parallax of 66.50 ± 0.11 mas yielding a distance of 15 parsecs or approximately 49 light years from Earth.<ref name="LEEUWEN"/> |
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It bore the traditional name ''Alderamin'', a contraction of the [[Arabic]] phrase ''الذراع اليمين'' ''al-dhirā‘ al-yamīn'', meaning "the right arm". In 2016, the [[International Astronomical Union]] organized a [[IAU Working Group on Star Names|Working Group on Star Names]] (WGSN)<ref name="WGSN"/> to catalog and standardize proper names for stars. The WGSN's first bulletin of July 2016<ref name="WGSN1"/> included a table of the first two batches of names approved by the WGSN; which included ''Alderamin'' for this star. |
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Given a surface temperature of 7,740 Kelvin, stellar models yield a total luminosity for the star of about 17 times the [[Solar luminosity|luminosity of the Sun]]. Alderamin has a radius of 2.3 times the [[Solar radius|Sun's radius]] and boasting a mass that is 1.74 that of the [[Sun]].<ref name=aass85_3_1015/> Like other stars in its class, it is slightly variable with a range in brightness of 0.06 magnitude, and is listed as a [[Delta Scuti variable]]. |
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== Visibility == |
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Alderamin has a very high rotation speed of at least 246 km/s, completing one complete revolution in less than 12 hours, with such a rapid turnover appearing to inhibit the differentiation of chemical elements usually seen in such stars.<ref name="HR1"/> By comparison, the Sun takes almost a month to turn on its axis. α Cep is also known to emit an amount of X radiation similar to the Sun, which along with other indicators suggests the existence of considerable magnetic activity—something unexpected (though not at all unusual) for a fast rotator. |
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With a declination in excess of 62 degrees north, Alpha Cephei never rises south of [[27th parallel south|−27° latitude]], which means for much of South America, Australia, South Africa, and all of New Zealand, the star stays below the horizon. The star is [[Circumpolar star|circumpolar]] throughout all of [[Europe]], northern Asia, Canada, and American cities as far south as [[San Diego]]. Since Alpha Cephei has an apparent magnitude of about 2.5, the star is the brightest in the constellation and is easily observable to the naked eye, even in [[light pollution|light-polluted]] cities. |
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=== Pole star === |
=== Pole star === |
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Alpha Cephei is located near the [[Precession|precessional path]] traced across the [[celestial sphere]] by the Earth's [[North Pole|North pole]]. That means that it periodically comes within 3° of being a [[pole star]],<ref name="KALER"/> a title currently held by [[Polaris]]. Alpha Cephei will next be the North Star in about the year 7500 AD.<ref name=Monthly1871/> The north pole of [[Mars]] points to the midpoint of the line connecting the star and [[Deneb]].<ref name="Barlow"/> |
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{| class="wikitable |
{| class="wikitable" style="margin: 1em auto 1em auto;" |
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! width="120" align="center"|Preceded by |
! width="120" align="center"|Preceded by |
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! width="160" align="center"|[[Pole Star]] |
! width="160" align="center"|[[Pole Star]] |
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|- |
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|align="center"|'''[[Iota Cephei]]''' |
|align="center"|'''[[Iota Cephei]]''' |
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|align="center"|circa |
|align="center"|circa 19,000 BC |
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|align="center"|'''[[Deneb]]''' |
|align="center"|'''[[Deneb]]''' |
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|} |
|} |
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== |
== Properties == |
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[[File:AlphaCepLightCurve.png|thumb|left|A [[light curve]] for Alpha Cephei, plotted from ''[[Transiting Exoplanet Survey Satellite|TESS]]'' data<ref name=MAST/>]] |
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Alderamin is a white [[Spectral classification#Class A|class A]] star, evolving off the [[main sequence]] into a [[subgiant]], probably on its way to becoming a [[red giant]] as its hydrogen supply runs low. On average, Alderamin has an [[apparent magnitude]] of 2.46.<ref name=AAVSO/> In 2007, the star's [[parallax]] was measured at {{val|66.50|0.11|ul=mas}} yielding a distance of 15 parsecs or approximately 49 light years from Earth.<ref name="LEEUWEN"/> |
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[[Interferometry]] by the [[CHARA array]] show that Alderamin has an oblate shape, its equatorial size measures {{solar radius|2.82|link=y}} and the polar radius measures {{solar radius|2.18}}. The star's temperature varies as well, from 8,440 [[Kelvin|K]] in the poles to 7,600 K in the equator.<ref name=vanBelle2006/> A more recent but less detailed measurement by the [[Navy Precision Optical Interferometer]] gives {{solar radius|2.71}}, which likely corresponds to the equatorial radius.<ref name=npoi/> Like other stars in its class, it is slightly variable with a range in brightness of 0.06 magnitude, and is listed as a [[Delta Scuti variable]]. |
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Alderamin has a very high rotation speed of at least 246 km/s, completing one complete revolution in less than 12 hours, with such a rapid turnover appearing to inhibit the differentiation of chemical elements usually seen in such stars.<ref name="HR1"/> By comparison, the Sun takes almost a month to turn on its axis. Alpha Cephei is also known to emit an amount of [[X radiation]] similar to the Sun, which along with other indicators suggests the existence of considerable magnetic activity—something unexpected (though not at all unusual) for a fast rotator. |
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=== Etymology === |
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The name Alderamin is a contraction of the Arabic phrase '''الذراع اليمين''' ''að-ðirā‘ al-yamīn'' "the right arm," with the first definite article transliterated literally as ''al'', as is often the case with Arabic star names. |
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== Etymology and cultural significance == |
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This star, along with [[Beta Cephei|β Cep]] (Alfirk) and [[Eta Cephei|η Cep]] (Alkidr) were '''Al Kawākib al Firḳ''' ('''الكوكب الفرق'''), meaning "the Stars of The Flock" by [[Ulug Beg]].<ref name=allen1963/><ref>Davis Jr., G. A., [http://adsabs.harvard.edu/abs/1944PA.....52....8D "The Pronunciations, Derivations, and Meanings of a Selected List of Star Names,"]''Popular Astronomy'', Vol. LII, No. 3, Oct. 1944, p. 16.</ref> |
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This star, along with [[Beta Cephei]] (Alfirk) and [[Eta Cephei]] (Alkidr) were ''al-Kawākib al-Firq'' (''الكواكب الفرق''), meaning "the Stars of the Flock" by [[Ulug Beg]].<ref name=allen1963/><ref name=PopAst/> |
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In [[Chinese |
In [[Chinese astronomy|Chinese]], {{lang|zh|天鈎}} ({{lang|zh-Latn|Tiān Gōu}}), meaning ''[[Rooftop (Chinese constellation)|Celestial Hook]]'', refers to an asterism consisting of α Cephei, [[4 Cephei]], [[HD 194298]], [[Eta Cephei]], [[Theta Cephei]], [[Xi Cephei]], [[26 Cephei]], [[Iota Cephei]] and [[Omicron Cephei]].<ref name=zh/> Consequently, the [[Chinese star names|Chinese name]] for Alpha Cephei itself is {{lang|zh|天鈎五}} ({{lang|zh-Latn|Tiān Gōu wu}}, {{langx|en|the Fifth Star of the Celestial Hook}}.).<ref name=lcsd/> |
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==Namesakes== |
===Namesakes=== |
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[[USS Alderamin (AK-116)]] was a [[United States Navy]] [[Crater class cargo ship]] named after the star. |
[[USS Alderamin (AK-116)]] was a [[United States Navy]] [[Crater class cargo ship]] named after the star. |
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==See also== |
==See also== |
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*[[List of nearest bright stars]] |
* [[List of nearest bright stars]] |
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* [[Lists of stars]] in the constellation [[List of stars in Draco|Draco]] |
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* [[Stellar classification#Class A|Class A Stars]] |
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* [[Dwarf star]] |
* [[Dwarf star]] |
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{{Reflist|colwidth=25em|refs= |
{{Reflist|colwidth=25em|refs= |
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<ref name=lcsd>{{in lang|zh}} [http://www.lcsd.gov.hk/CE/Museum/Space/Research/StarName/c_research_chinengstars_ala_alz.htm 香港太空館 – 研究資源 – 亮星中英對照表] {{webarchive|url=https://web.archive.org/web/20081025110153/http://www.lcsd.gov.hk/CE/Museum/Space/Research/StarName/c_research_chinengstars_ala_alz.htm |date=2008-10-25 }}, Hong Kong Space Museum. Accessed on line November 23, 2010.</ref> |
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<ref name=aaa361_614>{{citation | last1=Pizzolato | first1=N. | last2=Maggio | first2=A. | last3=Sciortino | first3=S. | title=Evolution of X-ray activity of 1-3 Msun late-type stars in early post-main-sequence phases | journal=Astronomy and Astrophysics | volume=361 | pages=614–628 |date=September 2000 | bibcode=2000A&A...361..614P }}</ref> |
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<ref name=zh>{{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}}.</ref> |
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<ref name="HR1">{{cite web | title=Bright Star Catalogue, 5th Revised Ed. (Hoffleit+, 1991) | work=[[VizieR]] | publisher=[[Centre de Données astronomiques de Strasbourg]] | url=http://vizier.u-strasbg.fr/viz-bin/VizieR-S?HR%208162 | accessdate=2010-12-20 }}</ref> |
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<ref name=PopAst>Davis Jr., G. A., [http://adsabs.harvard.edu/abs/1944PA.....52....8D "The Pronunciations, Derivations, and Meanings of a Selected List of Star Names,"]''Popular Astronomy'', Vol. LII, No. 3, Oct. 1944, p. 16.</ref> |
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<ref name="LEEUWEN">{{cite journal | title=Hipparcos, the New Reduction | author=van Leeuwen, F |date=November 2007 | publisher=[[Centre de Données astronomiques de Strasbourg]] | pages=653–664 | issue=2 | volume=474 | url=http://vizier.u-strasbg.fr/viz-bin/VizieR-S?HIP%20105199 | doi=10.1051/0004-6361:20078357 | journal=Astronomy and Astrophysics | bibcode=2007A&A...474..653V | accessdate=2010-12-19 |arxiv = 0708.1752 }}</ref> |
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<ref name="Barlow">{{cite book |
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<ref name="MERMILLIOD">{{cite journal | author=Mermilliod, J.-C. | title=Compilation of Eggen's UBV data, transformed to UBV (unpublished) | journal=Catalogue of Eggen's UBV data. | year=1986 | bibcode=1986EgUBV........0M }}</ref> |
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| last=Barlow |first=N. G. |url=https://archive.org/details/marsintroduction00barl_258 |
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| title=Mars: An introduction to its interior, surface and atmosphere |date=2008 |
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| publisher=[[Cambridge University Press]] |isbn=978-0-521-85226-5 |
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| page=[https://archive.org/details/marsintroduction00barl_258/page/n30 21] |url-access=limited}}</ref> |
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<ref name=Monthly1871>{{citation |
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<ref name="SIMBAD">{{cite web | url=http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=Alderamin&submit=SIMBAD+search | title=SIMBAD query result: NAME ALDERAMIN -- Variable Star | publisher=Centre de Données astronomiques de Strasbourg | accessdate=2010-12-20 }}</ref> |
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| title=Our Monthly | year=1871 | volume=4 | page=53 |
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| publisher=Presbyterian Magazine Company | postscript=. |
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| url=https://books.google.com/books?id=KdEQAAAAIAAJ&pg=PA53 }}</ref> |
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<ref name="KALER">{{cite web |
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| title=ALDERAMIN (Alpha Cephei) |
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| work=Stars | publisher=[[University of Illinois]] |
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| first1=James B. | last1=Kaler | author-link=James B. Kaler |
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| url=http://stars.astro.illinois.edu/sow/alderamin.html | access-date=2018-04-25 |
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| archive-url=https://web.archive.org/web/20180208013546/http://stars.astro.illinois.edu/sow/alderamin.html |
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| archive-date=2018-02-08 | url-status=dead }}</ref> |
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<ref name="WGSN1">{{cite web |
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| url=http://www.pas.rochester.edu/~emamajek/WGSN/WGSN_bulletin1.pdf |
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| title=Bulletin of the IAU Working Group on Star Names, No. 1 |access-date=28 July 2016}}</ref> |
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<ref name="WGSN">{{cite web |
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| url=https://www.iau.org/science/scientific_bodies/working_groups/280/ |
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| title=IAU Working Group on Star Names (WGSN)|access-date=22 May 2016}}</ref> |
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<ref name=Kunitzsch>{{cite book |
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|last1=Kunitzsch |first1=Paul |
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|last2=Smart |first2=Tim |
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|date = 2006 |edition = 2nd rev. |
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|title = A Dictionary of Modern star Names: A Short Guide to 254 Star Names and Their Derivations |
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|publisher = Sky Pub |location = Cambridge, Massachusetts |
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|isbn = 978-1-931559-44-7 |
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}}</ref> |
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<ref name="IAU-CSN">{{cite web |
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| url=http://www.pas.rochester.edu/~emamajek/WGSN/IAU-CSN.txt |
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| title=IAU Catalog of Star Names |access-date=28 July 2016}}</ref> |
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<ref name=MAST>{{cite web |
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| title=MAST: Barbara A. Mikulski Archive for Space Telescopes |
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| url=https://mast.stsci.edu/portal/Mashup/Clients/Mast/Portal.html |
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| publisher=Space Telescope Science Institute |access-date=8 December 2021}}</ref> |
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<ref name=vanBelle2006>{{cite journal |
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| title=First Results from the CHARA Array. III. Oblateness, Rotational Velocity, and Gravity Darkening of Alderamin |
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| display-authors=1 | last1=van Belle | first1=G. T. |
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| last2=Ciardi | first2=D. R. | last3=ten Brummelaar | first3=T. |
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| last4=McAlister | first4=H. A. | last5=Ridgway | first5=S. T. |
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| last6=Berger | first6=D. H. | last7=Goldfinger | first7=P. J. |
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| last8=Sturmann | first8=J. | last9=Sturmann | first9=L. |
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| last10=Turner | first10=N. | last11=Boden | first11=A. F. |
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| last12=Thompson | first12=R. R. | last13=Coyne | first13=J. |
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| journal=The Astrophysical Journal |
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| volume=637 | issue=1 | pages=494–505 | date=January 2006 |
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| arxiv=astro-ph/0509827 | bibcode=2006ApJ...637..494V |
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| doi=10.1086/498334 | s2cid=6074944 }}</ref> |
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<ref name=npoi>{{cite journal | bibcode=2023AJ....166..268B | title=33 New Stellar Angular Diameters from the NPOI, and Nearly 180 NPOI Diameters as an Ensemble | last1=Baines | first1=Ellyn K. | author2=Clark, James H., III | last3=Schmitt | first3=Henrique R. | last4=Stone | first4=Jordan M. | last5=von Braun | first5=Kaspar | journal=The Astronomical Journal | date=2023 | volume=166 | issue=6 | page=268 | doi=10.3847/1538-3881/ad08be | doi-access=free }}</ref> |
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<ref name=aaa361_614>{{citation | last1=Pizzolato | first1=N. | last2=Maggio | first2=A. | last3=Sciortino | first3=S. | title=Evolution of X-ray activity of 1–3 Msun late-type stars in early post-main-sequence phases | journal=Astronomy and Astrophysics | volume=361 | pages=614–628 |date=September 2000 | bibcode=2000A&A...361..614P }}</ref> |
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<ref name="HR1">{{cite web | title=Bright Star Catalogue | edition=5th Revised | author=Hoffleit | display-authors=etal | date=1991 | work=[[VizieR]] | publisher=[[Centre de Données astronomiques de Strasbourg]] | url=http://vizier.u-strasbg.fr/viz-bin/VizieR-S?HR%208162 | access-date=2010-12-20 }}</ref> |
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<ref name="LEEUWEN">{{cite journal | title=Hipparcos, the New Reduction | author=van Leeuwen, F |date=November 2007 | pages=653–664 | issue=2 | volume=474 | url=http://vizier.u-strasbg.fr/viz-bin/VizieR-S?HIP%20105199 | doi=10.1051/0004-6361:20078357 | journal=Astronomy and Astrophysics | bibcode=2007A&A...474..653V | access-date=2010-12-19 |arxiv = 0708.1752 | s2cid=18759600 }}</ref> |
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<ref name="MERMILLIOD">{{cite journal | author=Mermilliod, J.-C. | title=Compilation of Eggen's UBV data, transformed to UBV (unpublished) | journal=Catalogue of Eggen's UBV Data | date=1986 | bibcode=1986EgUBV........0M }}</ref> |
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<ref name="SIMBAD">{{cite simbad | title=alf Cep | access-date=2010-12-20 }}</ref> |
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<ref name=aass85_3_1015>{{citation | last1=Malagnini | first1=M. L. | last2=Morossi | first2=C. | title=Accurate absolute luminosities, effective temperatures, radii, masses and surface gravities for a selected sample of field stars | journal=Astronomy and Astrophysics Supplement Series | volume=85 | issue=3 | pages=1015–1019 |date=November 1990 | bibcode=1990A&AS...85.1015M }}</ref> |
<ref name=aass85_3_1015>{{citation | last1=Malagnini | first1=M. L. | last2=Morossi | first2=C. | title=Accurate absolute luminosities, effective temperatures, radii, masses and surface gravities for a selected sample of field stars | journal=Astronomy and Astrophysics Supplement Series | volume=85 | issue=3 | pages=1015–1019 |date=November 1990 | bibcode=1990A&AS...85.1015M }}</ref> |
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<ref name=allen1963>{{cite book | last=Allen | first=R. H. | |
<ref name=allen1963>{{cite book | last=Allen | first=R. H. | date=1963 | author-link=Richard Hinckley Allen | title=Star Names: Their Lore and Meaning | url=https://archive.org/details/starnamestheirlo00alle/page/157 | access-date=2010-12-12 | edition=Reprint | publisher=Dover Publications Inc. | location=New York | isbn=0-486-21079-0 | page=[https://archive.org/details/starnamestheirlo00alle/page/157 157] | url-access=registration }}</ref> |
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<ref name=AAVSO>{{Cite web |title=VSX : Detail for alf Cep |url=https://www.aavso.org/vsx/index.php?view=detail.top&oid=52284 |access-date=2024-08-16 |website=[[AAVSO]]}}</ref> |
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<ref name=gcvs>{{cite journal|bibcode=2009yCat....102025S|title=VizieR Online Data Catalog: General Catalogue of Variable Stars (Samus+ 2007–2013)|journal=VizieR On-line Data Catalog: B/GCVS. Originally Published in: 2009yCat....102025S|volume=1|display-authors=etal|last1=Samus|first1=N. N.|last2=Durlevich|first2=O. V.|year=2009}}</ref> |
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<ref name=gray>{{cite journal|bibcode=2003AJ....126.2048G|arxiv=astro-ph/0308182|title=Contributions to the Nearby Stars (NStars) Project: Spectroscopy of Stars Earlier than M0 within 40 Parsecs: The Northern Sample. I|journal=The Astronomical Journal|volume=126|issue=4|pages=2048|last1=Gray|first1=R. O.|last2=Corbally|first2=C. J.|last3=Garrison|first3=R. F.|last4=McFadden|first4=M. T.|last5=Robinson|first5=P. E.|year=2003|doi=10.1086/378365|s2cid=119417105}}</ref> |
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}} |
}} |
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== External links == |
== External links == |
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* {{cite web | title=ALDERAMIN (Alpha Cephei) | work=Stars | publisher=University of Illinois | first1=James B. | last1=Kaler | url=http://stars.astro.illinois.edu/sow/alderamin.html | |
* {{cite web | title=ALDERAMIN (Alpha Cephei) | work=Stars | publisher=[[University of Illinois]] | first1=James B. | last1=Kaler | url=http://stars.astro.illinois.edu/sow/alderamin.html | access-date=2010-12-20 | archive-url=https://web.archive.org/web/20180208013546/http://stars.astro.illinois.edu/sow/alderamin.html | archive-date=2018-02-08 | url-status=dead }} |
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*NASA's: [http://www-istp.gsfc.nasa.gov/stargaze/Sprecess.htm History of Precession] |
*NASA's: [http://www-istp.gsfc.nasa.gov/stargaze/Sprecess.htm History of Precession] |
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* |
*Crystallinks: [http://www.crystalinks.com/precession.html Precession of the Equinoxes] |
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{{Sky|21|18|34.8|+|62|35|08|48.8}} |
{{Sky|21|18|34.8|+|62|35|08|48.8}} |
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{{Nearest bright star systems|5.}} |
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{{Stars of Cepheus}} |
{{Stars of Cepheus}} |
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{{DEFAULTSORT:Alpha Cephei}} |
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[[Category:Bayer objects|Cephei, Alpha]] |
[[Category:Bayer objects|Cephei, Alpha]] |
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[[Category:Cepheus (constellation)]] |
[[Category:Cepheus (constellation)]] |
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[[Category:A-type subgiants]] |
[[Category:A-type subgiants]] |
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[[Category:Northern pole stars]] |
[[Category:Northern pole stars]] |
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[[Category:Stars with proper names]] |
[[Category:Stars with proper names|Alderamin]] |
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[[Category:Castor Moving Group]] |
[[Category:Castor Moving Group]] |
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[[Category:Flamsteed objects]] |
[[Category:Flamsteed objects|Cephei, 05]] |
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[[Category:Henry Draper Catalogue objects]] |
[[Category:Henry Draper Catalogue objects|203280]] |
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[[Category: |
[[Category:Bright Star Catalogue objects|8162]] |
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[[Category:Durchmusterung objects]] |
[[Category:Durchmusterung objects|BD+61 2111]] |
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[[Category:Hipparcos objects]] |
[[Category:Hipparcos objects|105199]] |
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[[Category:Suspected variables]] |
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[[Category:Delta Scuti variables]] |
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[[Category:Gliese and GJ objects|0826]] |
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Latest revision as of 02:35, 26 October 2024
  | |
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Cepheus |
| Right ascension | 21h 18m 34.7715s[1] |
| Declination | +62° 35′ 08.061″[1] |
| Apparent magnitude (V) | 2.46[2] |
| Characteristics | |
| Spectral type | A8Vn[3] or A7IV-V[4] |
| U−B color index | +0.12[5] |
| B−V color index | +0.21[5] |
| Variable type | suspected δ Sct[6] |
| Astrometry | |
| Radial velocity (Rv) | −10[1] km/s |
| Proper motion (μ) | RA: +150.55[7] mas/yr Dec.: 49.09[7] mas/yr |
| Parallax (π) | 66.50 ± 0.11 mas[7] |
| Distance | 49.05 ± 0.08 ly (15.04 ± 0.02 pc) |
| Absolute magnitude (MV) | 1.57[8] |
| Details[4] | |
| Mass | 2.00±0.15 M☉ |
| Radius | 2.175±0.046 (polar) 2.823±0.097 (equator) R☉ |
| Luminosity | 17[9] L☉ |
| Surface gravity (log g) | 3.99[9] cgs |
| Temperature | 8,440+430 −700 (polar) 7,600 (equator) K |
| Metallicity [Fe/H] | 0.09 dex |
| Rotation | 12.11±0.26 h |
| Rotational velocity (v sin i) | 283±19 km/s |
| Age | 820 Myr |
| Other designations | |
| Database references | |
| SIMBAD | data |
Alpha Cephei (α Cephei, abbreviated Alpha Cep, α Cep), officially named Alderamin /ælˈdɛrəmɪn/,[10][11] is a second magnitude star in the constellation of Cepheus near the northern pole. The star is relatively close to Earth at 49 light years (ly) and drifting closer with a heliocentric radial velocity of about −16 km/s.
Nomenclature
[edit]α Cephei (Latinised to Alpha Cephei) is the star's Bayer designation. It has a Flamsteed designation of 5 Cephei.
It bore the traditional name Alderamin, a contraction of the Arabic phrase الذراع اليمين al-dhirā‘ al-yamīn, meaning "the right arm". In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN)[12] to catalog and standardize proper names for stars. The WGSN's first bulletin of July 2016[13] included a table of the first two batches of names approved by the WGSN; which included Alderamin for this star.
Visibility
[edit]With a declination in excess of 62 degrees north, Alpha Cephei never rises south of −27° latitude, which means for much of South America, Australia, South Africa, and all of New Zealand, the star stays below the horizon. The star is circumpolar throughout all of Europe, northern Asia, Canada, and American cities as far south as San Diego. Since Alpha Cephei has an apparent magnitude of about 2.5, the star is the brightest in the constellation and is easily observable to the naked eye, even in light-polluted cities.
Pole star
[edit]Alpha Cephei is located near the precessional path traced across the celestial sphere by the Earth's North pole. That means that it periodically comes within 3° of being a pole star,[14] a title currently held by Polaris. Alpha Cephei will next be the North Star in about the year 7500 AD.[15] The north pole of Mars points to the midpoint of the line connecting the star and Deneb.[16]
| Preceded by | Pole Star | Succeeded by |
|---|---|---|
| Iota Cephei | circa 19,000 BC | Deneb |
Properties
[edit]
Alderamin is a white class A star, evolving off the main sequence into a subgiant, probably on its way to becoming a red giant as its hydrogen supply runs low. On average, Alderamin has an apparent magnitude of 2.46.[2] In 2007, the star's parallax was measured at 66.50±0.11 mas yielding a distance of 15 parsecs or approximately 49 light years from Earth.[7]
Interferometry by the CHARA array show that Alderamin has an oblate shape, its equatorial size measures 2.82 R☉ and the polar radius measures 2.18 R☉. The star's temperature varies as well, from 8,440 K in the poles to 7,600 K in the equator.[4] A more recent but less detailed measurement by the Navy Precision Optical Interferometer gives 2.71 R☉, which likely corresponds to the equatorial radius.[18] Like other stars in its class, it is slightly variable with a range in brightness of 0.06 magnitude, and is listed as a Delta Scuti variable.
Alderamin has a very high rotation speed of at least 246 km/s, completing one complete revolution in less than 12 hours, with such a rapid turnover appearing to inhibit the differentiation of chemical elements usually seen in such stars.[19] By comparison, the Sun takes almost a month to turn on its axis. Alpha Cephei is also known to emit an amount of X radiation similar to the Sun, which along with other indicators suggests the existence of considerable magnetic activity—something unexpected (though not at all unusual) for a fast rotator.
Etymology and cultural significance
[edit]This star, along with Beta Cephei (Alfirk) and Eta Cephei (Alkidr) were al-Kawākib al-Firq (الكواكب الفرق), meaning "the Stars of the Flock" by Ulug Beg.[20][21]
In Chinese, 天鈎 (Tiān Gōu), meaning Celestial Hook, refers to an asterism consisting of α Cephei, 4 Cephei, HD 194298, Eta Cephei, Theta Cephei, Xi Cephei, 26 Cephei, Iota Cephei and Omicron Cephei.[22] Consequently, the Chinese name for Alpha Cephei itself is 天鈎五 (Tiān Gōu wu, English: the Fifth Star of the Celestial Hook.).[23]
Namesakes
[edit]USS Alderamin (AK-116) was a United States Navy Crater class cargo ship named after the star.
See also
[edit]References
[edit]- ^ a b c d "alf Cep". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2010-12-20.
- ^ a b "VSX : Detail for alf Cep". AAVSO. Retrieved 2024-08-16.
- ^ Gray, R. O.; Corbally, C. J.; Garrison, R. F.; McFadden, M. T.; Robinson, P. E. (2003). "Contributions to the Nearby Stars (NStars) Project: Spectroscopy of Stars Earlier than M0 within 40 Parsecs: The Northern Sample. I". The Astronomical Journal. 126 (4): 2048. arXiv:astro-ph/0308182. Bibcode:2003AJ....126.2048G. doi:10.1086/378365. S2CID 119417105.
- ^ a b c van Belle, G. T.; et al. (January 2006). "First Results from the CHARA Array. III. Oblateness, Rotational Velocity, and Gravity Darkening of Alderamin". The Astrophysical Journal. 637 (1): 494–505. arXiv:astro-ph/0509827. Bibcode:2006ApJ...637..494V. doi:10.1086/498334. S2CID 6074944.
- ^ a b Mermilliod, J.-C. (1986). "Compilation of Eggen's UBV data, transformed to UBV (unpublished)". Catalogue of Eggen's UBV Data. Bibcode:1986EgUBV........0M.
- ^ Samus, N. N.; Durlevich, O. V.; et al. (2009). "VizieR Online Data Catalog: General Catalogue of Variable Stars (Samus+ 2007–2013)". VizieR On-line Data Catalog: B/GCVS. Originally Published in: 2009yCat....102025S. 1. Bibcode:2009yCat....102025S.
- ^ a b c d van Leeuwen, F (November 2007). "Hipparcos, the New Reduction". Astronomy and Astrophysics. 474 (2): 653–664. arXiv:0708.1752. Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357. S2CID 18759600. Retrieved 2010-12-19.
- ^ Pizzolato, N.; Maggio, A.; Sciortino, S. (September 2000), "Evolution of X-ray activity of 1–3 Msun late-type stars in early post-main-sequence phases", Astronomy and Astrophysics, 361: 614–628, Bibcode:2000A&A...361..614P
- ^ a b Malagnini, M. L.; Morossi, C. (November 1990), "Accurate absolute luminosities, effective temperatures, radii, masses and surface gravities for a selected sample of field stars", Astronomy and Astrophysics Supplement Series, 85 (3): 1015–1019, Bibcode:1990A&AS...85.1015M
- ^ Kunitzsch, Paul; Smart, Tim (2006). A Dictionary of Modern star Names: A Short Guide to 254 Star Names and Their Derivations (2nd rev. ed.). Cambridge, Massachusetts: Sky Pub. ISBN 978-1-931559-44-7.
- ^ "IAU Catalog of Star Names". Retrieved 28 July 2016.
- ^ "IAU Working Group on Star Names (WGSN)". Retrieved 22 May 2016.
- ^ "Bulletin of the IAU Working Group on Star Names, No. 1" (PDF). Retrieved 28 July 2016.
- ^ Kaler, James B. "ALDERAMIN (Alpha Cephei)". Stars. University of Illinois. Archived from the original on 2018-02-08. Retrieved 2018-04-25.
- ^ Our Monthly, vol. 4, Presbyterian Magazine Company, 1871, p. 53.
- ^ Barlow, N. G. (2008). Mars: An introduction to its interior, surface and atmosphere. Cambridge University Press. p. 21. ISBN 978-0-521-85226-5.
- ^ "MAST: Barbara A. Mikulski Archive for Space Telescopes". Space Telescope Science Institute. Retrieved 8 December 2021.
- ^ Baines, Ellyn K.; Clark, James H., III; Schmitt, Henrique R.; Stone, Jordan M.; von Braun, Kaspar (2023). "33 New Stellar Angular Diameters from the NPOI, and Nearly 180 NPOI Diameters as an Ensemble". The Astronomical Journal. 166 (6): 268. Bibcode:2023AJ....166..268B. doi:10.3847/1538-3881/ad08be.
{{cite journal}}: CS1 maint: multiple names: authors list (link) - ^ Hoffleit; et al. (1991). "Bright Star Catalogue". VizieR (5th Revised ed.). Centre de Données astronomiques de Strasbourg. Retrieved 2010-12-20.
- ^ Allen, R. H. (1963). Star Names: Their Lore and Meaning (Reprint ed.). New York: Dover Publications Inc. p. 157. ISBN 0-486-21079-0. Retrieved 2010-12-12.
- ^ Davis Jr., G. A., "The Pronunciations, Derivations, and Meanings of a Selected List of Star Names,"Popular Astronomy, Vol. LII, No. 3, Oct. 1944, p. 16.
- ^ (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.
- ^ (in Chinese) 香港太空館 – 研究資源 – 亮星中英對照表 Archived 2008-10-25 at the Wayback Machine, Hong Kong Space Museum. Accessed on line November 23, 2010.
External links
[edit]- Kaler, James B. "ALDERAMIN (Alpha Cephei)". Stars. University of Illinois. Archived from the original on 2018-02-08. Retrieved 2010-12-20.
- NASA's: History of Precession
- Crystallinks: Precession of the Equinoxes
