| 词条 | Beta Cephei | ||||||
| 释义 |
| name=β Cephei }}{{Starbox image | image={{Location mark |image=Cepheus constellation map.svg |alt= |label= |position=right |width=240 |x=703 |y=693 |float=center |mark=Cercle rouge 100%.svg |mark_width=12 |mark_link=Beta Cephei }} |caption=Location of β Cephei (circled) }}{{Starbox observe | epoch = J2000 | ra = {{RA|21|28|39.59685}}[1] | dec = {{DEC|+70|33|38.5747}}[1] | appmag_v = 3.16 – 3.27[3] | constell = Cepheus }}{{Starbox character | class = B1 IV[4] | b-v = –0.22[5] | u-b = –0.95[5] | variable = β Cep[3] }}{{Starbox astrometry | radial_v = –8.2[8] | prop_mo_ra = +12.54[1] | prop_mo_dec = +8.39[1] | parallax = 4.76 | p_error = 0.30 | parallax_footnote = [1] | absmag_v = –3.03[4] }}{{Starbox detail | mass = 12.2 – 19.5[4] | radius = 5.6[4] | metal_fe = –0.23[15] | gravity = 4.05[4] | luminosity = 15,100[4] | temperature = 27,000[4] | rotational_velocity = 28[19] | age_myr = 8.7[4] }}{{Starbox catalog | names = Alfirk, β Cep, 8 Cephei, AAVSO 2127+70, AG+70°738, BD+69°1173, CCDM J21287+7034A, FK5 809, GSC 04465-02643, HD 205021, HIP 106032, HR 8238, SAO 10057, WDS J21287+7034 }}{{Starbox reference | Simbad=Beta+Cephei }}{{Starbox end}}{{Sky|21|28|39.60|+|70|33|39.0}} Beta Cephei (β Cephei, abbreviated Beta Cep, β Cep) is a triple star system of the third magnitude in the constellation of Cepheus. Based on parallax measurements obtained during the Hipparcos mission, it is approximately 690 light-years distant from the Sun. It is the prototype of the Beta Cephei variable stars. It consists of a binary pair (designated Beta Cephei A) together with a third companion (B). The binary's two components are themselves designated Beta Cephei Aa (also named Alfirk[1]) and Ab. Nomenclatureβ Cephei (Latinised to Beta Cephei) is the system's Bayer designation. The designations of the two constituents as Beta Cephei A and B, and those of A's components - Beta Cephei Aa and Ab - derive from the convention used by the Washington Multiplicity Catalog (WMC) for multiple star systems, and adopted by the International Astronomical Union (IAU).[2]Beta Cephei bore the traditional name Alfirk, derived from the Arabic الفرقة al-firqah "the flock" (of sheep). With Alpha Cephei (Alderamin) and Eta Cephei (Alkidr), they were Al Kawākib al Firḳ الكوكب الفرق "the stars of the flock" by Ulug Beg.[3][4] In 2016, the IAU organized a Working Group on Star Names (WGSN)[5] to catalogue and standardize proper names for stars. The WGSN decided to attribute proper names to individual stars rather than entire multiple systems.[6] It approved the name Alfirk for the component Beta Cephei Aa on 21 August 2016 and it is now so included in the List of IAU-approved Star Names.[1] VisibilityLike the star Epsilon Draconis in the constellation of Draco, Beta Cephei is visible primarily in the northern hemisphere, given its extreme northern declination of 70 degrees and 34 minutes. It 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. It is 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 polluted cities, though in rural locations the star should be easily observable. Pole StarBeta Cephei is a visible star located within 5° of the precessional path traced across the celestial sphere by the Earth's North pole. During the same period Iota Cephei will also be within 5° of the precessional path, on the other side so that both are in contention as pole stars, a title currently held by unambiguously by Polaris.
PropertiesBeta Cephei is a triple star comprising a spectroscopic binary with a magnitude 8 optical companion.[28] Its magnitude varies between +3.16 and +3.27 with a period of 0.19048 days.[3] Beta Cephei Aa is a blue subgiant star with a stellar classification of B1 IV. It has previously been classified with either a main sequence or giant luminosity class. This star has a radius that has been estimated at {{Solar radius|link=y|6}} and a mass of {{Solar mass|link=y|12}}. Like most high-mass B-class stars, Beta Cephei Aa is a relatively young star with an estimated age of just a few million years. Like the majority of giant stars, it rotates slowly on its axis with a rotational velocity of 7 deg/day, a speed which takes the star approximately 51 days to make one complete revolution. Beta Cephei Ab is a Be star in an 85-year orbit with the giant primary.[4] It has been resolved using speckle interferometry at a distance of 0.25" in 1972.[32] B Cephei B is a magnitude 7.8 A2 main sequence star 13.6" distant.[4] VariabilityBeta Cephei pulsates regularly every 4 hours 34 minutes, producing a variation in its visual brightness of 0.11 magnitudes. It is the prototype of the Beta Cephei class of variables, hot main sequence and giant stars that pulsate analogously to Cepheid variables but with the pulsations driven by iron opacity rather than by helium.[3] References1. ^1 {{cite web | url=https://www.iau.org/public/themes/naming_stars/ | title=Naming Stars |publisher=IAU.org |accessdate=18 June 2018}} [7][8][9][10][11][12][13][14][15]2. ^{{cite arXiv |title=On the naming convention used for multiple star systems and extrasolar planets |date=2010 |eprint=1012.0707 |class=astro-ph.SR |last1= Hessman |first1=F. V. |last2= Dhillon |first2=V. S. |last3= Winget |first3=D. E. |last4= Schreiber |first4=M. R. |last5= Horne |first5=K. |last6= Marsh |first6=T. R. |last7= Guenther |first7=E. |last8= Schwope |first8=A. |last9= Heber |first9=U. }} 3. ^{{cite book | last=Allen | first=R. H. | date=1963 | authorlink=Richard Hinckley Allen | title=Star Names: Their Lore and Meaning | url=http://penelope.uchicago.edu/Thayer/E/Gazetteer/Topics/astronomy/_Texts/secondary/ALLSTA/Cepheus*.html | accessdate=2010-12-12 | edition=Reprint | publisher=Dover Publications Inc. | location=New York | isbn=0-486-21079-0 | page=157 }} 4. ^{{cite journal|bibcode=1944PA.....52....8D|title=The Pronunciations, Derivations, and Meanings of a Selected List of Star Names|journal=Popular Astronomy|volume=52|pages=8|author1=Davis|first1=George R.|year=1944}} 5. ^{{citation | url=https://www.iau.org/science/scientific_bodies/working_groups/280/ | title=IAU Working Group on Star Names (WGSN) | publisher=International Astronomical Union | accessdate=22 May 2016 | postscript=. }} 6. ^{{cite web | url=https://www.iau.org/static/science/scientific_bodies/working_groups/280/wg-starnames-triennial-report-2015-2018.pdf | page=5 | title=WG Triennial Report (2015-2018) - Star Names |accessdate=2018-07-14}} 7. ^1 {{cite journal|bibcode=1972ApJ...173L...1G|title=Speckle Interferometry: Diffraction-Limited Measurements of Nine Stars with the 200-INCH Telescope|journal=Astrophysical Journal|volume=173|pages=L1|author1=Gezari|first1=D. Y.|last2=Labeyrie|first2=A.|last3=Stachnik|first3=R. V.|year=1972|doi=10.1086/180906}} 8. ^1 2 3 4 {{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|author1=Samus|first1=N. N.|last2=Durlevich|first2=O. V.|year=2009}} 9. ^1 2 {{cite journal | last1=Mermilliod | first1=J.-C. | title=Compilation of Eggen's UBV data, transformed to UBV (unpublished) | journal=Catalogue of Eggen's UBV data | date=1986 | publisher=SIMBAD | bibcode=1986EgUBV........0M }} 10. ^1 2 3 4 5 {{cite journal | 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 | doi=10.1051/0004-6361:20078357 | journal=Astronomy and Astrophysics | bibcode=2007A&A...474..653V | arxiv = 0708.1752 }} 11. ^1 {{cite journal | display-authors=etal | last1=Cenarro | first1=A. J. | last2=Peletier | first2=R. F. | last3=Sánchez-Blázquez | first3=P. | last4=Selam | first4=S. O. | last5=Toloba | title=Medium-resolution Isaac Newton Telescope library of empirical spectra – II. The stellar atmospheric parameters | journal=Monthly Notices of the Royal Astronomical Society | date=2007 | volume=374 | issue=2 | pages=664–690 | bibcode=2007MNRAS.374..664C | doi=10.1111/j.1365-2966.2006.11196.x | arxiv=astro-ph/0611618 }} 12. ^1 {{cite web | last1=Hoffleit | title=Bright Star Catalogue | work=VizieR | edition=5th revised | date=1991 | publisher=Centre de Données astronomiques de Strasbourg | url=http://vizier.u-strasbg.fr/viz-bin/VizieR-S?HR%208238 | accessdate=2010-12-26 }} 13. ^1 2 3 4 5 6 7 8 9 10 {{cite journal|bibcode=2014A&A...566A...7N|arxiv=1412.1418|title=Fundamental properties of nearby single early B-type stars|journal=Astronomy & Astrophysics|volume=566|pages=A7|author1=Nieva|first1=María-Fernanda|last2=Przybilla|first2=Norbert|year=2014|doi=10.1051/0004-6361/201423373}} 14. ^1 {{cite journal|bibcode=1953GCRV..C......0W|title=General catalogue of stellar radial velocities|journal=Washington|author1=Wilson|first1=Ralph Elmer|year=1953}} 15. ^1 {{cite book |last=Norton |first=Arthur P. |title=Norton's Star Atlas |date=1973 |page=118 |isbn=0-85248-900-5 |quote=Fixed. A is a spectroscopic binary.}} }} External links
14 : Cepheus (constellation)|Bayer objects|Beta Cephei variables|B-type main-sequence stars|Stars with proper names|Spectroscopic binaries|Triple stars|Flamsteed objects|Hipparcos objects|A-type main-sequence stars|Be stars|HR objects|Henry Draper Catalogue objects|Durchmusterung objects |
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