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'''經典造父變星'''（也稱為'''第一星族造父變星'''、'''第一型造父變星'''、或'''[[仙王座δ型變星|仙王座δ變星]]'''）是[[造父變星]]的一種。它們是[[金屬量#第一星族星|第一星族星]]，有著周期從數天至數月，質量是太陽4-20倍的[[變星]]<ref name=turner96>Turner, David G.[http://adsabs.harvard.edu/abs/1996JRASC..90...82T "The Progenitors of Classical Cepheid Variables"] {{Wayback|url=http://adsabs.harvard.edu/abs/1996JRASC..90...82T |date=20181106233128 }}. ''JRASC'' (1996)</ref>，光度可以達到太陽的100,000倍<ref name=turner10>Turner, David G.[http://adsabs.harvard.edu/cgi-bin/bib_query?arXiv:0912.4864 "The PL calibration for Milky Way Cepheids and its implications for the distance scale"]. ''Ap&SS'' (2010)</ref>。經典造父變星是[[光譜類型]]在F6-K2的黃超巨星，在脈動週期中的半徑變化可以達到數百萬公里（大約是[[船底座I]]的25%）<ref>Rodgers, A. W. [http://articles.adsabs.harvard.edu//full/1957MNRAS.117...85R/0000092.000.html "Radius variation and population type of cepheid variables"] {{Wayback|url=http://articles.adsabs.harvard.edu//full/1957MNRAS.117...85R/0000092.000.html |date=20190610094057 }}. ''Monthly Notices of the Royal Astronomical Society''. 117 (1956) 84–94</ref><ref name="strohmeier1972">W. Strohmeier, ''Variable Stars'', Pergamon (1972)</ref>。

經典脈動變星的[[光度]]和脈動週期之間存在著明確的關聯性<ref name=udalski99>Udalski, A.; Soszynski, I.; Szymanski, M.; Kubiak, M.; Pietrzynski, G.; Wozniak, P.; Zebrun, K.[http://adsabs.harvard.edu/abs/1999AcA....49..223U "The Optical Gravitational Lensing Experiment. Cepheids in the Magellanic Clouds. IV. Catalog of Cepheids from the Large Magellanic Cloud"] {{Wayback|url=http://adsabs.harvard.edu/abs/1999AcA....49..223U |date=20190418185933 }}. ''Acta A.'' (1999)</ref><ref name=sos08>Soszynski, I.; Poleski, R.; Udalski, A.; Szymanski, M. K.; Kubiak, M.; Pietrzynski, G.; Wyrzykowski, L.; Szewczyk, O.; Ulaczyk, K. [http://adsabs.harvard.edu/abs/2008AcA....58..163S "The Optical Gravitational Lensing Experiment. The OGLE-III Catalog of Variable Stars. I. Classical Cepheids in the Large Magellanic Cloud"] {{Wayback|url=http://adsabs.harvard.edu/abs/2008AcA....58..163S |date=20190418185937 }}. ''Acta A.'' (2008)</ref>，可靠的造父變星成為可行的[[標準燭光]]，建立起銀河和[[宇宙距離尺度|河外星系距離指標]]<ref name=freedman2001/><ref name=tammannsandage2008/><ref name=majaess2009/><ref name=freedman2010>Freedman, Wendy L.; Madore, Barry F. [http://adsabs.harvard.edu/abs/2010ARA%26A..48..673F "The Hubble Constant"] {{Wayback|url=http://adsabs.harvard.edu/abs/2010ARA%26A..48..673F |date=20170720215306 }}, ''Annual Review of Astronomy and Astrophysics'', 2010</ref>。[[哈伯太空望遠鏡]]觀測經典造父變星使[[哈伯定律]]成為更為可靠的制約因素<ref name="freedman2001">Freedman, W. et al. [http://adsabs.harvard.edu/abs/2001ApJ...553...47F "Final Results from the Hubble Space Telescope Key Project to Measure the Hubble Constant"] {{Wayback|url=http://adsabs.harvard.edu/abs/2001ApJ...553...47F |date=20190729111450 }}, ''The Astrophysical Journal'', Volume 553, Issue 1, pp. 47–72 (2001)</ref><ref name="tammannsandage2008" /><ref name="freedman2010" /><ref name="ngeow2006" /><ref name="macririess2009" />。經典造父變星也用來闡明我們的銀河系，像是太陽位於銀河盤面的上方，以及銀河系在本地的螺旋結構<ref name="majaess2009">Majaess D. J., Turner D. G., Lane D. J. [http://adsabs.harvard.edu/abs/2009arXiv0903.4206M "Characteristics of the Galaxy according to Cepheids"] {{Wayback|url=http://adsabs.harvard.edu/abs/2009arXiv0903.4206M |date=20160208172649 }}, ''Monthly Notices of the Royal Astronomical Society'' (2009)</ref>。

在[[銀河系]]內已知的經典造父變星超過700顆<ref name="cox1980">Cox, John P., ''Theory of Stellar Pulsations'', Princeton (1980)</ref>，在外星系也已經發現了數千顆。[[哈伯太空望遠鏡]]已經確認出距離一億光年的[[NGC 4603]]內的經典造父變星<ref name="HST_NGC_4603_Cepheid_Distance">Jeffrey A. Newman, Stephen E. Zepf, Marc Davis, Wendy L. Freedman, Barry F. Madore, Peter B. Stetson, N. Silbermann  and Randy Phelps [http://iopscience.iop.org/0004-637X/523/2/506/ "A Cepheid Distance to NGC 4603 in Centaurus"]. ''The Astrophysical Journal''. 523 (1999) 506–520</ref>。

==發現==
在1784年9月10日，[[愛德華·皮戈特]]檢測到[[天桴四|天鷹座η]]的光度變化，這是第一顆被描述的經典造父變星。但是，這一種造父變星卻以幾個月後由[[约翰·古德利克]]發現的變星[[造父一]]為代表。[[造父一]]也是驗證周光關係時特別重要的一顆造父變星，因為他的距離是造父變星中最精確的，這要歸功於它的成員都在[[星團]]之中<ref
name=dezeeuw1999>de Zeeuw, P. T.; Hoogerwerf, R.; de Bruijne, J. H. J.; Brown, A. G. A.; Blaauw, A. (1999). [http://adsabs.harvard.edu/abs/1999AJ....117..354D ''A HIPPARCOS Census of the Nearby OB Associations''] {{Wayback|url=http://adsabs.harvard.edu/abs/1999AJ....117..354D |date=20080202043410 }}, AJ</ref><ref name=majaess2012>Majaess, D.; Turner, D.; Gieren, W. (2012). [http://adsabs.harvard.edu/abs/2012ApJ...747..145M ''New Evidence Supporting Cluster Membership for the Keystone Calibrator Delta Cephei''] {{Wayback|url=http://adsabs.harvard.edu/abs/2012ApJ...747..145M |date=20160118143506 }}, ApJ</ref>，並且可以從[[哈伯太空望遠鏡]]/[[依巴谷衛星]]得到可靠的視差<ref name=benedict2002/>。

==周光關係==
經典造父變星的光度與它的變化週期有著直接的關係。脈動週期越長，光度也越明亮。這種周光關係是[[亨麗愛塔·勒維特]]在研究了[[麥哲倫雲]]的數千顆變星之後，於1908年發現的<ref>Leavitt, Henrietta S. [http://www.adsabs.harvard.edu/abs/1908AnHar..60...87L "1777 Variables in the Magellanic Clouds"] {{Wayback|url=http://www.adsabs.harvard.edu/abs/1908AnHar..60...87L |date=20180809114603 }}. ''Annals of Harvard College Observatory''. LX(IV) (1908) 87–110</ref>。她於1912年與更進一步的證據發表<ref>Miss Leavitt in Pickering, Edward C. [http://adsabs.harvard.edu/abs/1912HarCi.173....1L "Periods of 25 Variable Stars in the Small Magellanic Cloud"] {{Wayback|url=http://adsabs.harvard.edu/abs/1912HarCi.173....1L |date=20180809111227 }} ''Harvard College Observatory Circular'' 173 (1912) 1–3.</ref>。一旦校準了[[周光關係]]，只要知道脈動周期就可以建立給定的這顆造父變星的光度，然後從它的視星等就可以得知距離。從[[埃希納·赫茨普龍]]開始，20世紀有許多的天文學家都在校正周光關係<ref>Hertzsprung, E., "Über die räumliche Verteilung der Veränderlichen vom &delta; Cephei-Typus." ''Astronomischen Nachrichten'', 196 p. 201–210 (1913)</ref>。校準期間的周光關係一直都有問題，不過本尼克等人在2007年使用哈伯太空望遠鏡精確的測量了10顆鄰近的經典造父變星的視差，確定了銀河系內穩定的周光關係<ref name=benedict2007>Benedict, G. Fritz et al. [http://adsabs.harvard.edu/abs/2007AJ....133.1810B "Hubble Space Telescope Fine Guidance Sensor Parallaxes of Galactic Cepheid Variable Stars: Period-Luminosity Relations"] {{Wayback|url=http://adsabs.harvard.edu/abs/2007AJ....133.1810B |date=20160123123325 }}, ''The Astronomical Journal'', Volume 133, Issue 4, pp. 1810-1827 (2007)</ref>。同時，在2008年，[[歐洲南天天文台|ESO]]的天文學家使用[[迴光]]測量埋置在星雲中的[[船尾座RS]]的距離，精確度達到只有1%的誤差<ref>Kervella, Pierre: [http://www.eso.org/public/outreach/press-rel/pr-2008/pr-05-08.html ''Light echoes whisper the distance to a star''] {{webarchive|url=https://web.archive.org/web/20090807111715/http://www.eso.org/public/outreach/press-rel/pr-2008/pr-05-08.html |date=2009-08-07 }}</ref>。但是，後者的發現一直是文獻中爭論的主題<ref>Bond, H. E., Sparks, W. B. [http://adsabs.harvard.edu/abs/2009A%26A...495..371B "On geometric distance determination to the Cepheid RS Puppis from its light echoes"] {{Wayback|url=http://adsabs.harvard.edu/abs/2009A%26A...495..371B |date=20170306123550 }}, ''Astronomy and Astrophysics'', Volume 495, Issue 2, 2009, pp.371-377</ref>。

下面的經典造父變星周光關係公式，<math>P</math>是脈動週期， <math>M_v</math>是[[絕對星等]]。這是建立在[[哈伯太空望遠鏡]]對鄰近的10顆造父變星以[[視差|三角視差]]測距的結果：

: <math> M_v = -2.43\pm0.12 (\log_{10}(P) - 1) - (4.05 \pm 0.02) \, </math>

此處<math>P</math>的測量單位是天。
<ref name=benedict2002>Benedict, G. Fritz; McArthur, B. E.; Fredrick, L. W.; Harrison, T. E.; Slesnick, C. L.; Rhee, J.; Patterson, R. J.; Skrutskie, M. F.; Franz, O. G.; Wasserman, L. H.; Jefferys, W. H.; Nelan, E.; van Altena, W.; Shelus, P. J.; Hemenway, P. D.; Duncombe, R. L.; Story, D.; Whipple, A. L.; Bradley, A. J. (2002). [http://adsabs.harvard.edu/abs/2002AJ....124.1695B ''Astrometry with the Hubble Space Telescope: A Parallax of the Fundamental Distance Calibrator δ Cephei''] {{Wayback|url=http://adsabs.harvard.edu/abs/2002AJ....124.1695B |date=20181005081416 }}, AJ</ref><ref
name=benedict2007/>。使用下列的公式也可以計算經典造父變星的距離：
: <math> 5\log_{10}{d}=V+ (3.34) \log_{10}{P} - (2.45) (V-I) + 7.52 \,. </math><ref name=benedict2007/>
: <math> 5\log_{10}{d}=V+ (3.37) \log_{10}{P} - (2.55) (V-I) + 7.48 \,. </math><ref name=majaess2011>Majaess, Daniel; Turner, David; Moni Bidin, Christian; Mauro, Francesco; Geisler, Douglas; Gieren, Wolfgang; Minniti, Dante; Chené, André-Nicolas; Lucas, Philip; Borissova, Jura; Kurtev, Radostn; Dékány, Istvan; Saito, Roberto K. [http://adsabs.harvard.edu/abs/2011ApJ...741L..27M "New Evidence Supporting Membership for TW Nor in Lyngå 6 and the Centaurus Spiral Arm"] {{Wayback|url=http://adsabs.harvard.edu/abs/2011ApJ...741L..27M |date=20170310051039 }}, ApJ Letters'', Volume 741, Issue 2, article id. L2 (2011)</ref>。
<math>I</math>和<math>V</math>分別表示近紅外線和視覺上（可見光）的平均星等。

==以造父變星測量距離的不確定性==
綑綁在造父變星之間，對距離測量的不確定因素主要是：周光關係在不同通帶的本質，零點和斜率的關係這兩者都會衝擊到[[金屬量|豐度]]，以及光度計的汙染（混合）和衰減的變化規律（通常是未知的），都會影響到造父變星測量的距離。所有這些主題在文獻中都有爭議<ref>Feast, Michael W. & Robin M. Catchpole. [http://adsabs.harvard.edu/abs/1997MNRAS.286L...1F "The Cepheid period-luminosity zero-point from Hipparcos trigonometrical parallaxes"] {{Wayback|url=http://adsabs.harvard.edu/abs/1997MNRAS.286L...1F |date=20160123031748 }}. ''[[Monthly Notices of the Royal Astronomical Society]]''. 286 (1997) L 1–5.</ref><ref name=turner10/><ref name=tammannsandage2008>Tammann, G. A.; Sandage, A.; Reindl, B. [http://adsabs.harvard.edu/abs/2008A%26ARv..15..289T "The expansion field: the value of H 0"] {{Wayback|url=http://adsabs.harvard.edu/abs/2008A%26ARv..15..289T |date=20190820103253 }}, ''Annual Review of Astronomy and Astrophysics'', 2008</ref><ref name=ngeow2006>Ngeow, C., Kanbur, S. M. [http://adsabs.harvard.edu/abs/2006ApJ...642L..29N "The Hubble Constant from Type Ia Supernovae Calibrated with the Linear and Nonlinear Cepheid Period-Luminosity Relations"] {{Wayback|url=http://adsabs.harvard.edu/abs/2006ApJ...642L..29N |date=20190820101711 }}, ''The Astrophysical Journal'', 2006</ref><ref name=stanekudalski1999>Stanek, K. Z., Udalski, A. [http://adsabs.harvard.edu/abs/1999astro.ph..9346S "The Optical Gravitational Lensing Experiment. Investigating the Influence of Blending on the Cepheid Distance Scale with Cepheids in the Large Magellanic Cloud"] {{Wayback|url=http://adsabs.harvard.edu/abs/1999astro.ph..9346S |date=20181005080000 }}, ''ApJ'', 1999</ref><ref name=udalski2001>Udalski, A. et al. [http://adsabs.harvard.edu/abs/2001AcA....51..221U "The Optical Gravitational Lensing Experiment. Cepheids in the Galaxy IC1613: No Dependence of the Period-Luminosity Relation on Metallicity"] {{Wayback|url=http://adsabs.harvard.edu/abs/2001AcA....51..221U |date=20181005081026 }}, ''Acta Astronomica'', 2001</ref><ref name=macri2006>Macri, L. M.; Stanek, K. Z.; Bersier, D.; Greenhill, L. J.; Reid, M. J. [http://adsabs.harvard.edu/abs/2006ApJ...652.1133M "A New Cepheid Distance to the Maser-Host Galaxy NGC 4258 and Its Implications for the Hubble Constant"] {{Wayback|url=http://adsabs.harvard.edu/abs/2006ApJ...652.1133M |date=20190921035036 }}, ''The Astrophysical Journal'', 2006</ref><ref name=bono2008>Bono, G.; Caputo, F.; Fiorentino, G.; Marconi, M.; Musella, I.[http://adsabs.harvard.edu/abs/2008ApJ...684..102B "Cepheids in External Galaxies. I. The Maser-Host Galaxy NGC 4258 and the Metallicity Dependence of Period-Luminosity and Period-Wesenheit Relations"] {{Wayback|url=http://adsabs.harvard.edu/abs/2008ApJ...684..102B |date=20181005080631 }}, ''The Astrophysical Journal'', 2008</ref><ref name=majaess2009b>Majaess, D.; Turner, D.; Lane, D. [http://adsabs.harvard.edu/abs/2009AcA....59..403M "Type II Cepheids as Extragalactic Distance Candles"] {{Wayback|url=http://adsabs.harvard.edu/abs/2009AcA....59..403M |date=20191020081937 }}, ''Acta Astronomica'', 2009</ref><ref name=madore2009>Madore, Barry F., Freedman, Wendy L. [http://adsabs.harvard.edu/abs/2009ApJ...696.1498M " Concerning the Slope of the Cepheid Period-Luminosity Relation"] {{Wayback|url=http://adsabs.harvard.edu/abs/2009ApJ...696.1498M |date=20181005080752 }}, ''The Astrophysical Journal'', 2009</ref><ref name=scowcroft2009>Scowcroft, V.; Bersier, D.; Mould, J. R.; Wood, P. R. [http://adsabs.harvard.edu/abs/2009MNRAS.396.1287S "The effect of metallicity on Cepheid magnitudes and the distance to M33"] {{Wayback|url=http://adsabs.harvard.edu/abs/2009MNRAS.396.1287S |date=20181005074142 }}, ''Monthly Notices of the Royal Astronomical Society'', Volume 396, Issue 3, pp. 1287-1296, 2009</ref><ref name=majaess2010>Majaess, D. [http://adsabs.harvard.edu/abs/2010AcA....60..121M "The Cepheids of Centaurus A (NGC 5128) and Implications for H0"] {{Wayback|url=http://adsabs.harvard.edu/abs/2010AcA....60..121M |date=20191020081936 }}, ''Acta Astronomica'', 2010</ref>。

這些未解決的事項已經導致[[哈勃定律|哈伯常數]]的值（以經典造父變星建立）在60 km/s/Mpc和80公里/s/Mpc之間不等<ref name=freedman2001/><ref name=tammannsandage2008/><ref name=freedman2010/><ref name=ngeow2006/><ref name=macririess2009/>，解決此一差異是天文學當今的首要問題之一，因為宇宙學的宇宙參數受到哈伯常數數值精確的制約和影響<ref name="freedman2010"/><ref name=macririess2009>Macri, Lucas M.; Riess, Adam G. [http://adsabs.harvard.edu/abs/2009AIPC.1170...23M "The SH0ES Project: Observations of Cepheids in NGC 4258 and Type Ia SN Hosts"] {{Wayback|url=http://adsabs.harvard.edu/abs/2009AIPC.1170...23M |date=20190820101713 }}, ''STELLAR PULSATION: CHALLENGES FOR THEORY AND OBSERVATION'', 2009</ref>。

==例子==
一些相當明亮的經典造父變星，展示出肉眼可以分辨的光度變化，包括：[[天鷹座η]]、[[雙子座ζ]]、[[劍魚座β]]，和據以命名的原型[[造父一]]。距離最近的經典造父變星是北極星（[[勾陳一]]），雖然這顆恆星展示出許多特性，但是它的距離仍是一個爭議很多的議題<ref name=turner2009>Turner, D. [http://adsabs.harvard.edu/abs/2010ARA%26A..48..673F "Polaris and its Kin"] {{Wayback|url=http://adsabs.harvard.edu/abs/2010ARA%26A..48..673F |date=20170720215306 }}, ''STELLAR PULSATION: CHALLENGES FOR THEORY AND OBSERVATION'', 2009</ref>。

==相關條目==
*[[第二型造父變星]]
*[[天琴座RR型變星]]

==參考資料==
{{Reflist|2}}

==外部連結==
*[https://web.archive.org/web/20101009205927/http://www.institute-of-brilliant-failures.com/ The Cepheid Distance Scale: A History, by Nick Allen]
*[https://web.archive.org/web/20100521050807/http://seds.org/~spider/spider/ScholarX/variables.html SEDS: Variable Stars]
*[http://crocus.physics.mcmaster.ca/Cepheid/HomePage.html McMaster Cepheid Photometry and Radial Velocity Data Archive] {{Wayback|url=http://crocus.physics.mcmaster.ca/Cepheid/HomePage.html |date=20070309055222 }}
*[http://www.aavso.org/ American Association of Variable Star Observers] {{Wayback|url=http://www.aavso.org/ |date=20100202050715 }}
*[[Stellar pulsation theory - Regular versus irregular variability]]

{{Variable star topics}}

{{DEFAULTSORT:Cepheid Variable}}
[[Category:造父變星]]
[[Category:天体测量学]]
[[Category:標準燭光]]
[[Category:變星]]

[[ru:Цефеиды]]