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| {{Starbox begin
| | Nice to meet you, I am Marvella Shryock. For years I've been operating as a payroll clerk. North Dakota is exactly where me and my spouse live. Body building is what my family and I appreciate.<br><br>my web page - [http://Www.Eyelevelfederalway.com/xe/index.php?mid=Promotions&page=1&document_srl=571267 std testing at home] |
| | name=Alfirk, β Cep
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| }}
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| {{Starbox image
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| | image=<div style="position: relative">[[File:Cepheus constellation map.svg|250px|Location of Beta Cephei]]
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| <div style="position: absolute; left:68%; top:55%">[[File:Cercle rouge 100%.svg|12px]]</div>
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| </div> <!--http://meta.wikimedia.org/wiki/Help:Composite_images -->
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| | caption=Location of β Cephei (center right).
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| }}
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| {{Starbox observe
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| | epoch = J2000
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| | ra = {{RA|21|28|39.5971}}<ref name="SIMBAD"/>
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| | dec = {{DEC|+70|33|38.578}}<ref name="SIMBAD"/>
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| | appmag_v = 3.1438<ref name="LEEUWEN"/>
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| | constell = [[Cepheus (constellation)|Cepheus]]
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| }}
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| {{Starbox character
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| | class = B2IIIev<ref name="SIMBAD"/>
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| | b-v = –0.22<ref name="MERMILLIOD"/>
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| | u-b = –0.95<ref name="MERMILLIOD"/>
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| | variable = [[Beta Cephei variable]]
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| }}
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| {{Starbox astrometry
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| | radial_v = –8.2<ref name="SIMBAD" />
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| | prop_mo_ra = +12.54<ref name="LEEUWEN"/>
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| | prop_mo_dec = +8.39<ref name="LEEUWEN"/>
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| | parallax = 4.76
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| | p_error = 0.30
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| | parallax_footnote = <ref name="LEEUWEN"/>
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| | absmag_v = –3.468<ref name="LEEUWEN"/><!-- Computed value? Not listed at ref. -->
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| }}
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| {{Starbox detail
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| | mass = 12<ref name="KALER"/>
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| | radius = 9.0<ref name="STEBBINS"/>
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| | metal_fe = –0.23<ref name="CENARRO"/>
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| | gravity = 3.80<ref name=aaa515_A74/>
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| | age_myr =
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| | luminosity = 36,900<ref>See Notes Section for calculations</ref>
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| | temperature = 26,700<ref name="KALER"/>
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| | rotational_velocity = 28<ref name="HR1"/>
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| }}
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| {{Starbox catalog
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| | names = Alfirk, [[Flamsteed designation|8 Cep]], [[American Association of Variable Star Observers|AAVSO]] 2127+70, [[Astronomische Gesellschaft Katalog|AG]]+70° 738, [[Bonner Durchmusterung|BD]]+69 1173, [[Catalog of Components of Double and Multiple Stars|CCDM]] J21287+7034A, [[Catalogues of Fundamental Stars|FK5]] 809, [[Guide Star Catalog|GSC]] 04465-02643, [[Henry Draper catalogue|HD]] 205021, [[Hipparcos catalogue|HIP]] 106032, [[Harvard Revised catalogue|HR]] 8238, [[Smithsonian Astrophysical Observatory Star Catalog|SAO]] 10057, [[Washington Double Star Catalog|WDS]] J21287+7034 Aa,Ab.<ref name="SIMBAD"/>
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| }}
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| {{Starbox reference
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| | Simbad=Beta+Cephei
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| }}
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| {{Starbox end}}
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| {{Sky|21|28|39.60|+|70|33|39.0}}
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| '''Beta Cephei''' (β Cep, β Cephei) is a third magnitude [[star]] in the [[constellation]] [[Cepheus (constellation)|Cepheus]]. It has the traditional name '''Alfirk''' ([[Arabic language|Arabic]] الفرقة ''al-firqah''), meaning ''"The Flock"'' (referring to a flock of sheep) This star, along with [[Alpha Cephei|α Cep]] (Alderamin) and [[Eta Cephei|η Cep]] (Alkidr), were '''Al Kawākib al Firḳ''' ('''الكوكب الفرق'''), meaning "the Stars of The Flock" by [[Ulug Beg]].<ref>{{cite book
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| | last=Allen | first=R. H. | year=1963
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| | authorlink=Richard Hinckley Allen
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| | title=Star Names: Their Lore and Meaning
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| | url=http://penelope.uchicago.edu/Thayer/E/Gazetteer/Topics/astronomy/_Texts/secondary/ALLSTA/Cepheus*.html
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| | accessdate=2010-12-12 | edition=Reprint
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| | publisher=Dover Publications Inc
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| | location=New York | isbn=0-486-21079-0 | page=157 }}</ref><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> Beta Cephei is the prototype of the [[Beta Cephei variable]] stars.
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| == Visibility ==
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| Like the star [[Epsilon Draconis]] in the [[constellation]] of [[Draco (constellation)|Draco]], Alfirk is visible primarily in the [[northern hemisphere]], given its extreme northern [[declination]] of 70 degrees and 34 minutes. The star is nevertheless visible to most observers throughout the world reaching as far south as cities like [[Harare]] in [[Zimbabwe]], [[Santa Cruz de la Sierra]] in [[Bolivia]] or other settlements north ± 19° South latitude. The star is [[Circumpolar star|circumpolar]] throughout all of [[Europe]], northern Asia, and North American cities as far south as [[Guadalajara]] in west central [[Mexico]]. All other locations around the globe having a [[latitude]] greater than ± 20° North will notice that the star is always visible in the night sky. Because Beta Cephei is a faint third magnitude star, it may be difficult to identify in most [[light pollution|light polluted]] cities, though in rural locations the star should be easily observable.
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| == Properties ==
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| Beta Cephei is a [[Multiple star#Triple star systems|triple star]] comprising a [[Binary star#Spectroscopic binaries|spectroscopic binary]] with a [[apparent magnitude|magnitude]] 8 optical companion.<ref name="Nor">{{cite book
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| |last=Norton
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| |first=Arthur P.
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| |title=Norton's Star Atlas
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| |year=1973
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| |page=118
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| |isbn=0-85248-900-5
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| |quote=Fixed. A is a spectroscopic binary.}}</ref> Its [[apparent magnitude|magnitude]] varies between +3.15 and +3.21 with a period of 0.1904844 days.
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| Beta Cephei A is a [[blue giant]] star with a [[stellar classification]] listed in the [[SIMBAD]] astronomical database as B2IIIev.<ref name="SIMBAD"/> The suffix "ev" comes from the [[Yerkes spectral classification scheme|Yerkes classification system]] and stands for [[Stellar classification#Spectral peculiarities|"Spectral emission that exhibits variability"]]. This giant star has a radius that has been estimated at 9[[Solar radius|R<sub>☉</sub>]] and a mass of 12[[Solar mass|M<sub>☉</sub>]]. Like most high mass [[Stellar classification#Class B|B class]] stars, β Cep is a relatively young star with an estimated age of around 50 million years old. Like the majority of giant stars, Beta Cephei A rotates slowly on its axis with a rotational velocity of 28 km/s, a speed which takes the star approximately 51 days to make one complete revolution.
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| In 2007, Floor van Leeuwen and his team recalibrated the star's [[apparent magnitude]] at 3.1438 and updated the star's parallax to 4.76 ± 0.30 [[Milliarcseconds|mas]] yielding a distance of 210.1 [[parsecs]] (pc) or approximately 685 [[light year]]s (ly) from [[Earth]].<ref name="LEEUWEN"/> The previous estimate from the [[Hipparcos]] mission had placed the star at about 595 ly. Given a surface temperature of 26,700 Kelvin, theoretical calculations yield a total luminosity for the star of about 36,900[[Solar luminosity|L<sub>☉</sub>]].<ref name="NOTELUMINOSITY" group="note">The formula for the bolometric luminosity of Beta Cephei is as follows:
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| :<math>\frac{L_{\rm A}}{L_{\odot}} = {\left ( \frac{R_{\rm A}}{R_{\odot}} \right )}^2 {\left ( \frac{T_{\rm A}}{T_{\odot}} \right )}^4</math> where... A = Alfirk, L = Luminosity, R = Radius and T = Temperature.
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| Therefore:
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| :<math>\frac{L_{\rm A}}{L_{\odot}} = {\left ( {\frac{9}{1}} \right )}^2 {\left ( {\frac{26,700}{5,778}} \right )}^4 = 36,933 L_{\odot}</math>
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| Note: Luminosity calculations are highly dependent on size and distance variables.</ref>
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| ==See also==
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| * [[List of stars in Draco]]
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| * [[Stellar classification#Class B|Class B Stars]]
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| * [[Variable star]]
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| * [[Star system]]
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| == Notes ==
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| <references group="note" />
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| == References ==
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| {{Reflist|colwidth=25em|refs=
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| <ref name="SIMBAD">{{citation | url=http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=bet+cep&submit=SIMBAD+search | title=V* bet Cep -- Variable Star of beta Cep type | work=SIMBAD Astronomical Object Database | publisher=Centre de Données astronomiques de Strasbourg | accessdate=2010-12-26 }}</ref>
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| <ref name="MERMILLIOD">{{citation | last1=Mermilliod | first1=J.-C. | title=Compilation of Eggen's UBV data, transformed to UBV (unpublished) | journal=Catalogue of Eggen's UBV data. | year=1986 | publisher=SIMBAD | bibcode=1986EgUBV........0M }}</ref>
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| <ref name="LEEUWEN">{{citation | title=Hipparcos, the New Reduction | last1=van Leeuwen | first1=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%20106032 | doi=10.1051/0004-6361:20078357 | journal=Astronomy and Astrophysics | bibcode=2007A&A...474..653V | accessdate=2010-12-26 |arxiv = 0708.1752 }}</ref>
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| <ref name="KALER">{{citation | title=ALFIRK (Beta Cephei) | publisher=University of Illinois | first1=James B. | last1=Kaler | work=Stars | url=http://stars.astro.illinois.edu/sow/alfirk.html | accessdate=2010-12-26 }}</ref>
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| <ref name="STEBBINS">{{citation | title=Six-color photometry of stars. VIII. The pulsating star Beta Cephei | last1=Stebbins | first1=J. | last2=Kron | first2=G. E. | journal=The Astrophysical Journal | volume=120 | page=189 |date=September 1954 | format=PDF | publisher=GCPD | doi=10.1086/145902 | bibcode=1954ApJ...120..189S }}</ref>
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| <ref name="CENARRO">{{citation | display-authors=1 | last1=Cenarro | first1=A. J. | last2=Peletier | first2=R. F. | last3=Sánchez-Blázquez | first3=P. | last4=Selam | first4=S. O. | last5=Toloba | last6=et al | title=Medium-resolution Isaac Newton Telescope library of empirical spectra - II. The stellar atmospheric parameters | journal=Monthly Notices of the Royal Astronomical Society | year=2007 | volume=374 | issue=2 | pages=664–690 | format=PDF | bibcode=2007MNRAS.374..664C | doi=10.1111/j.1365-2966.2006.11196.x | arxiv=astro-ph/0611618 }}</ref>
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| <ref name="HR1">{{citation | last1=Hoffleit | title=Bright Star Catalogue | work=[[VizieR]] | edition=5th revised | year=1991 | publisher=[[Centre de Données astronomiques de Strasbourg]] | url=http://vizier.u-strasbg.fr/viz-bin/VizieR-S?HR%208238 | accessdate=2010-12-26 }}</ref>
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| <ref name=aaa515_A74>{{citation | display-authors=1 | last1=Lefever | first1=K. | last2=Puls | first2=J. | last3=Morel | first3=T. | last4=Aerts | first4=C. | last5=Decin | first5=L. | last6=Briquet | first6=M. | title=Spectroscopic determination of the fundamental parameters of 66 B-type stars in the field-of-view of the CoRoT satellite | journal=Astronomy and Astrophysics | volume=515 | page=A74 |date=June 2010 | doi=10.1051/0004-6361/200911956 | bibcode=2010A&A...515A..74L |arxiv = 0910.2851 }}</ref>
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| ==External links==
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| *Jim Kaler's Stars, University of Illinois:[http://stars.astro.illinois.edu/sow/alfirk.html ALFIRK (Beta Cephei)]
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| *AAVSO Variable Star of the Month, Winter 2005: [http://www.aavso.org/vsots_betacep The Beta Cephei Stars and Their Relatives]
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| *An Atlas of the Universe: [http://www.atlasoftheuniverse.com/orbits.html Multiple Star Orbits]
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| {{Stars of Cepheus}}
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| [[Category:Cepheus (constellation)]]
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| [[Category:Bayer objects|Cephei, Beta]]
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| [[Category:Beta Cephei variables]]
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| [[Category:B-type giants]]
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| [[Category:Stars with proper names]]
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| [[Category:Double stars]]
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| [[Category:Triple stars]]
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Nice to meet you, I am Marvella Shryock. For years I've been operating as a payroll clerk. North Dakota is exactly where me and my spouse live. Body building is what my family and I appreciate.
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