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{{ Infobox globular cluster
| name = 梅西耶71（M71）
| image = [[File:M71.jpg|250px]]
| caption = M71
| credit =
| epoch = [[J2000]]
| class = X-XI
| constellation = [[天箭座]]
| ra = {{RA|19|53|46.49}}<ref name=aj140_6_1830/>
| dec = {{DEC|+18|46|45.1}}<ref name=aj140_6_1830/>
| dist_ly = {{Convert|13.0|kly|kpc|abbr=on|lk=on}}<ref name=apj670_1_363/>
| appmag_v = 8.2<ref>{{cite web |url=https://messier.seds.org/m/m071.html |title=Messier 71 |access-date=30 April 2022 |website=SEDS Messier Catalog |archive-date=2022-07-23 |archive-url=https://web.archive.org/web/20220723093717/http://www.messier.seds.org/m/m071.html |dead-url=no }}</ref>
| size_v = 7.2'
| mass_msol = {{Val|1.7|e=4}}<ref name=mnras406_3_2000/>
| radius_ly = 13 ly<ref>distance × sin( diameter_angle / 2 ) = 13 ly. radius</ref>
| metal_fe = –0.78<ref name=apj742_1_51/>
| v_hb =
| age = 9-10 Gyr
| notes =
| names = M71, [[NGC天體表|NGC]] 6838、[[科林德目錄|Cr]] 409、GCl 115<ref name="simbad" />
}}

'''M71'''（也稱為'''梅西耶71'''或'''NGC 6838'''）是一個位於[[天球|北天]]小[[星座]][[天箭座]]的[[球狀星團]]。它是由{{link-en|Philippe Loys de Chéseaux}}於1745年發現的，並於1780年被[[查爾斯·梅西耶]]收錄其非[[彗星]]天體目錄中。1775年左右，在[[德國]][[德勒斯登]]的天文學家{{link-en|凱勒|Johann Gottfried Koehler}}也注意到了這個天體<ref>{{Cite web|title=New General Catalog Objects: NGC 6800 - 6849|url=https://cseligman.com/text/atlas/ngc68.htm#6838|access-date=2021-03-11|website=cseligman.com|archive-date=2022-07-06|archive-url=https://web.archive.org/web/20220706065550/https://cseligman.com/text/atlas/ngc68.htm#6838|dead-url=no}}</ref>。

這個星團距離地球大約12,000光年，跨度為{{convert|27|ly|pc|0}}。不規則[[變星]]''[[天箭座Z]]是它的成員之一<ref name="AAVSO"/>。

幾十年來（直到20世紀70年代），M71被認為是一個密集的[[疏散星團]]。主要原因是，它缺乏密集的中心壓縮，並且其恆星比古老的球狀星團通常具有更高的"[[金屬量]]"；此外，它缺少在大多數球狀星體中常見的"星團變星"，[[天琴座RR型變星|天琴座RR變星]]，因此被早期研究星團的[[天文學家]]歸類為疏散星團。然而，現代光度學的[[光度測定 (天文學)|光度測定]]在[[赫羅圖]]（溫度與光度圖）中檢測到一個短短的"[[水平分支]]"：這是球狀星團的特徵。分支的短小解釋了它缺少天琴座RR型變星的原因，是由於年齡在90-100億年間，還是個相對年輕的球狀星團。這可以解釋為何其缺乏許多或只有後期系列的恆星（[[星族#第一星族星|第一星族星]]）。因此，現在的M71就像在[[長蛇座]]的[[M68]]一樣，被認定為一個集中度非常鬆散的[[球狀星團]]。M71的質量約為{{solar mass|53,000|link=yes}}，[[光度]]約為19,000{{Solar luminosity}}<ref name="Dalgleish"/>。

[[File:M71map.png|thumbnail|標示出M71位置的星圖。]]

{{Commons category|Messier 71}}

== 相關條目 ==
* [[梅西耶天體列表]]

== 參考資料 ==
{{reflist|refs=
<ref name=aj140_6_1830>{{citation | display-authors=1 | last1=Goldsbury | first1=Ryan | last2=Richer | first2=Harvey B. | last3=Anderson | first3=Jay | last4=Dotter | first4=Aaron | last5=Sarajedini | first5=Ata | last6=Woodley | first6=Kristin | title=The ACS Survey of Galactic Globular Clusters. X. New Determinations of Centers for 65 Clusters | journal=The Astronomical Journal | volume=140 | issue=6 | pages=1830–1837 |date=December 2010 | doi=10.1088/0004-6256/140/6/1830 | bibcode=2010AJ....140.1830G | postscript=. |arxiv = 1008.2755 }}</ref>

<ref name=mnras406_3_2000>{{citation | last1=Marks | first1=Michael | last2=Kroupa | first2=Pavel | title=Initial conditions for globular clusters and assembly of the old globular cluster population of the Milky Way | journal=[[Monthly Notices of the Royal Astronomical Society]] | volume=406 | issue=3 | pages=2000–2012 |date=August 2010 | doi=10.1111/j.1365-2966.2010.16813.x | bibcode=2010MNRAS.406.2000M | postscript=. |arxiv = 1004.2255 }} Mass is from M<sub>PD</sub> on Table 1.</ref>

<ref name="simbad">{{cite simbad | title=M 71 | access-date=2006-11-17 }}</ref>

<ref name=apj670_1_363>{{citation | display-authors=1 | last1=Hessels | first1=J. W. T. | last2=Ransom | first2=S. M. | last3=Stairs | first3=I. H. | last4=Kaspi | first4=V. M. | last5=Freire | first5=P. C. C. | title=A 1.4 GHz Arecibo Survey for Pulsars in Globular Clusters | journal=The Astrophysical Journal | volume=670 | issue=1 | pages=363–378 |date=November 2007 | doi=10.1086/521780 | bibcode=2007ApJ...670..363H | postscript=. |arxiv = 0707.1602 }}</ref>

<ref name=apj742_1_51>{{citation | display-authors=1 | last1=Boyles | first1=J. | last2=Lorimer | first2=D. R. | last3=Turk | first3=P. J. | last4=Mnatsakanov | first4=R. | last5=Lynch | first5=R. S. | last6=Ransom | first6=S. M. | last7=Freire | first7=P. C. | last8=Belczynski | first8=K. | title=Young Radio Pulsars in Galactic Globular Clusters | journal=The Astrophysical Journal | volume=742 | issue=1 | page=51 |date=November 2011 | doi=10.1088/0004-637X/742/1/51 | bibcode=2011ApJ...742...51B | postscript=. |arxiv = 1108.4402 }}</ref>

<ref name="AAVSO">{{cite web |title=Z Sge |url=https://www.aavso.org/vsx/index.php?view=detail.top&oid=27350 |website=The International Variable Star Index |publisher=AAVSO |access-date=1 March 2021 |archive-date=2023-01-10 |archive-url=https://web.archive.org/web/20230110224945/https://www.aavso.org/vsx/index.php?view=detail.top&oid=27350 |dead-url=no }}</ref>

<ref name="Dalgleish">{{cite journal |last1=Dalgleish |first1=H. |last2=Kamann |first2=S. |last3=Usher |first3=C. |last4=Baumgardt |first4=H. |last5=Bastian |first5=N. |last6=Veitch-Michaelis |first6=J. |last7=Bellini |first7=A. |last8=Martocchia |first8=S. |last9=Da Costa |first9=G. S. |last10=Mackey |first10=D. |last11=Bellstedt |first11=S. |last12=Pastorello |first12=N. |last13=Cerulo |first13=P. |title=The WAGGS project-III. Discrepant mass-to-light ratios of Galactic globular clusters at high metallicity |journal=Monthly Notices of the Royal Astronomical Society |date=March 2020 |volume=492 |issue=3 |pages=3859-3871 |doi=10.1093/mnras/staa091 |url=https://ui.adsabs.harvard.edu/abs/2020MNRAS.492.3859D |access-date=1 March 2021 |doi-access=free |archive-date=2023-01-13 |archive-url=https://web.archive.org/web/20230113032908/https://ui.adsabs.harvard.edu/abs/2020MNRAS.492.3859D |dead-url=no }}</ref>

}}

== 外部連結 ==
* {{WikiSky}}
* [http://messier.seds.org/m/m071.html Messier71 @ SEDS Messier pages] {{Wayback|url=http://messier.seds.org/m/m071.html |date=20150421154930 }}
* [http://gclusters.altervista.org/cluster_4.php?ggc=M+71 Messier 71, Galactic Globular Clusters Database page] {{Wayback|url=http://gclusters.altervista.org/cluster_4.php?ggc=M+71 |date=20110522204135 }}
* [http://www.perseus.gr/Astro-DSO-NGC-6838.htm Messier 71, LRGB CCD image based on two hours total exposure] {{Wayback|url=http://www.perseus.gr/Astro-DSO-NGC-6838.htm |date=20100515124458 }}
* [http://www.spacetelescope.org/images/potw1018a/ Messier 71: an Unusual Globular Cluster] {{Wayback|url=http://www.spacetelescope.org/images/potw1018a/ |date=20201025052017 }}, [[ESA]]\[[Hubble Space Telescope|Hubble]] picture of the week.
* {{cite web|title=M71 – Globular Cluster|url=http://www.deepskyvideos.com/videos/messier/M71.html|work=Deep Sky Videos|publisher=[[Brady Haran]]|author=McCormac, James|author2=Szymanek, Nik|author-link2=Nik Szymanek|access-date=2022-07-06|archive-date=2022-07-11|archive-url=https://web.archive.org/web/20220711010236/http://www.deepskyvideos.com/videos/messier/M71.html|dead-url=no}}

{{Portal bar|天文學|恆星|太空}}
{{梅西耶天體}}
{{Ngc70}}
{{Sky|19|53|46.11|+|18|46|42.3|12000}}

[[Category:球狀星團|M071]]
[[Category:天箭座|M071]]
[[Category:梅西耶天體|071]]
[[Category:NGC天體|M071]]
[[Category:1745年發現的天體|?]]

M71 - 版本历史

imported>InternetArchiveBot：​补救2个来源，并将0个来源标记为失效。) #IABot (v2.0.9.3

imported>InternetArchiveBot：补救2个来源，并将0个来源标记为失效。) #IABot (v2.0.9.3