69.117.41.200: Removed link to Z Sagittae because it redirects to 15 Sagittae which is a different star and not a member of M71.

2025-08-10T17:16:33Z

Removed link to Z Sagittae because it redirects to 15 Sagittae which is a different star and not a member of M71.

New page

{{short description|Globular cluster in the constellation Sagitta}}
{{Multiple issues|
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{{Infobox globular cluster
| name = Messier 71
| image = Messier 71, an Unusual Globular Cluster.jpg
| caption = The globular cluster Messier 71 by the [[Hubble Space Telescope]].
| credit =
| epoch = [[J2000]]
| class = X-XI
| constellation = [[Sagitta]]
| 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}}</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, [[New General Catalogue|NGC]] 6838, [[Collinder catalog|Cr]] 409, GCl 115<ref name="simbad" />
}}

'''Messier 71''' (also known as '''M71''', '''NGC 6838''', or the '''Angelfish Cluster''') is a [[globular cluster]] in the small [[celestial hemisphere|northern]] [[constellation]] [[Sagitta]]. It was discovered by [[Philippe Loys de Chéseaux]] in 1745 and included by [[Charles Messier]] in his catalog of non-[[comet]]-like objects in 1780. It was also noted by [[Johann Gottfried Koehler|Koehler]] at [[Dresden]] around 1775.<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}}</ref> Messier 71 is also known as '''NGC 6839''', though this identification is very uncertain.<ref>{{Cite web |title=Your NED Search Results |url=https://ned.ipac.caltech.edu/cgi-bin/objsearch?objname=NGC_6839&extend=no&hconst=73&omegam=0.27&omegav=0.73&corr_z=1&out_csys=Equatorial&out_equinox=J2000.0&obj_sort=RA+or+Longitude&of=pre_text&zv_breaker=30000.0&list_limit=5&img_stamp=YES |access-date=2024-08-28 |website=ned.ipac.caltech.edu}}</ref>

This star cluster is about 13,000 [[light year]]s away from [[Earth]] and spans {{convert|27|ly|pc|0}}. The irregular [[variable star]] ''Z Sagittae'' is a member.<ref name="AAVSO" />

[[File:M71 Crop.png|left|thumb|The M71 globular cluster at the center is surrounded by a dense Milky Way star field.]]M71 was for many decades thought (until the 1970s) to be a densely packed [[open cluster]] and was classified as such by leading [[astronomer]]s in the field of star cluster research due to its lacking a dense central compression, and to its stars having more "[[Metallicity|metals]]" than is usual for an ancient globular cluster; furthermore, it lacks the [[RR Lyrae variable|RR Lyrae]] "cluster" variable stars that are common in most globulars. However, modern photometric [[Photometry (astronomy)|photometry]] has detected a short "[[horizontal branch]]" in the [[Hertzsprung-Russell diagram|H-R diagram]] (chart of temperature versus luminosity) which is characteristic of a globular cluster. The shortness of the branch explains the lack of RR Lyrae variables and is due to the globular's relatively young age of 9–10 billion years. Taking in many or only late series ([[Population I]]) stars explains relatively its stars. Hence today M71 is designated as a very loosely concentrated globular cluster, much like [[Messier 68|M68]] in [[Hydra (constellation)|Hydra]]. M71 has a mass of about {{solar mass|53,000|link=yes}} and a [[Luminosity#In astronomy|luminosity]] of around 19,000 {{lo|link=yes}}.<ref name="Dalgleish"/>
[[File:M71map.png|thumbnail|Map showing location of M71]]
{{Commons category|Messier 71}}

==See also==
* [[List of Messier objects]]
* [[NGC 6366]]
* [[NGC 6342]]

==References==
{{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 | s2cid=119183070 }}</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 | doi-access=free | bibcode=2010MNRAS.406.2000M | postscript=. |arxiv = 1004.2255 | s2cid=118652005 }} 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 | s2cid=16914232 }}</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 | s2cid=118649860 }}</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}}</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 |bibcode=2020MNRAS.492.3859D |doi-access=free |arxiv=2001.01810 }}</ref>

}}

== Gallery ==
<gallery>
File:M71.jpg|Till Credner and Sven Kohle, Calar Alto Observatory.
File:M71 - Noao-m71.jpg|M71 in visible light by the [[National Optical Astronomy Observatory|NOAO]].
File:NGC 6838 2MASS.jpg|M71 in [[infrared]] by the [[Astronomical survey|survey]] [[2MASS]].
File:NGC 6838 DSS.jpg|M71 in visible light by the [[Astronomical survey|survey]] [[Digitized Sky Survey|DSS]].
</gallery>

==External links==
* {{WikiSky}}
* [http://messier.seds.org/m/m071.html Messier71 @ SEDS Messier pages]
* [http://gclusters.altervista.org/cluster_4.php?ggc=M+71 Messier 71, Galactic Globular Clusters Database page]
* [http://www.perseus.gr/Astro-DSO-NGC-6838.htm Messier 71, LRGB CCD image based on two hours total exposure]
* [https://esahubble.org/images/potw1018a/ Messier 71: an Unusual Globular Cluster], [[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 }}

{{Portal bar|Astronomy|Stars|Outer space}}
{{Messier objects}}
{{NGC objects: 6001-7000}}
{{Sky|19|53|46.11|+|18|46|42.3|12000}}

[[Category:Globular clusters|Messier 071]]
[[Category:Sagitta|Messier 071]]
[[Category:Messier objects|071]]
[[Category:NGC objects|Messier 071]]
[[Category:Astronomical objects discovered in 1745|?]]

Messier 71 - Revision history

69.117.41.200: Removed link to Z Sagittae because it redirects to 15 Sagittae which is a different star and not a member of M71.