Editing Messier 92

{{Short description|Globular cluster in the constellation Hercules}}
{{Infobox globular cluster
| name = Messier 92
| image = M92 Hubble WikiSky.jpg
| image_size = 300px
| caption = Center of M92 by [[Hubble Space Telescope|HST]]; 1.44{{prime}} view
| credit =
| epoch = [[Epoch (astronomy)#Julian years and J2000|J2000]]
| class = IV<ref name="hcob849_11" />
| constellation = [[Hercules constellation|Hercules]]
| ra = {{RA|17|17|07.39}}<ref name="aj140_6_1830" />
| dec = {{DEC|+43|08|09.4}}<ref name="aj140_6_1830" />
| dist_ly = {{Convert|26.7|e3ly|kpc|abbr=on|lk=on}}<ref name="apj721_2_1790" />
| appmag_v = 6.4<ref>{{cite web |url=https://messier.seds.org/m/m092.html |title=Messier 92 |access-date=30 April 2022 |website=SEDS Messier Catalog}}</ref>
| size_v = 14' arc minutes
| mass_msol = {{Val|2.0|e=5}}<ref name="mnras406_3_2000" />
| radius_ly =54&nbsp;[[light-year|ly]]<ref>distance × sin( diameter_angle / 2 ) = 54 ly. radius</ref>
| v_hb =
| metal_fe = –2.32<ref name="mnras404_3_1203" />
| notes =
| names = M92, [[New General Catalogue|NGC]] 6341, GCl 59<ref name="simbad" />
}}
'''Messier 92''' (also known as '''M92''', '''M 92''', or '''NGC 6341''') is a [[globular cluster]] of stars in the northern [[constellation]] of [[Hercules (constellation)|Hercules]].

== Discovery ==
It was discovered by [[Johann Elert Bode]] on December 27, 1777, then published in the ''[[Berliner Astronomisches Jahrbuch]]'' during 1779.<ref>{{cite book |last1=Bode |title=Astronomisches Jahrbuch oder Ephemeriden für das Jahr 1782. |trans-title=Astronomical Yearbook or Ephemerides for the Year 1782. |date=1779 |publisher=George Jacob Decker |location=Berlin, (Germany) |page=156 |url=https://play.google.com/books/reader?id=fRJ_e8z9nSoC&pg=GBS.RA1-PA156&hl=en |language=German |chapter=Zweyter Theil 20. Beobachtung des Kometen von 1779 und Entdeckung einiger neuen Nebelsterne [Second Part. 20. Observation of the comet of 1779 and discovery of some new nebulae]}} From p. 156: ''" […] ich am 27. Decemb. 1777 einen ''neuen'', mir nicht bekannten ''Nebelfleck im Herkules'', südwestlich unter dem Stern ⍳ an dessen Fusse entdeckt, der sich in einer mehrentheils runden Figur mit einem blassen Lichtschimmer zeigt."'' ( […] on the 27th December 1777, I discovered a ''new nebula'', which was unknown to me, ''in Hercules'', southwest under the star ⍳ [iota] at his feet, which appears as a mostly round shape with a pale glimmer.)</ref><ref name="kanas2007" /> It was inadvertently rediscovered by [[Charles Messier]] on March 18, 1781,{{efn|On March 18}} and added as the 92nd entry in his catalogue.<ref name="garfinckle1997" /> William Herschel first resolved individual stars in 1783.

== Visibility ==
It is one of the brighter of its sort in apparent magnitude in the northern hemisphere and in its [[absolute magnitude]] in [[Milky Way|the galaxy]], but it is often overlooked by amateur astronomers due to angular proximity to bright cluster [[Messier 13]], about 20% closer. Though when compared to M13, M92 is only slightly less bright, but about 1/3 less extended. It is visible to the [[naked eye]] under very good viewing conditions.<ref name="maa" /> With a small telescope, M92 can be seen as a nebulous smudge even in a severely light-polluted sky, and can be further resolved in darker conditions. 

== Characteristics ==
It is also one of the galaxy's oldest clusters. It is around {{Convert|16|e3ly|kpc|abbr=on|lk=on}} above/below the [[galactic plane]] and {{Convert|33|e3ly|kpc|abbr=on|lk=off}} from the [[Galactic Center]].<ref name="aj133_3_1041" /> It is about 26,700 [[light-year]]s away from the [[Solar System]].The half-light radius, or radius containing the upper half of its light emission, is 1.09&nbsp;[[arcminute]]s ({{prime}}), while the tidal radius, the broadest standard measure, is 15.17{{prime}}. It appears only [[flattening|slightly flattened]]: its minor axis is about 89% ± 3% of the major.<ref name="apj721_2_1790" />

Characteristic of other globulars, it has little of the elements other than hydrogen and helium; astronomers term this low [[metallicity]]. Specifically, relative to the [[Sun]], its iron abundance is [Fe/H]&nbsp;= &ndash;2.32&nbsp;[[dex (decimal exponent)|dex]],<ref name="aj133_3_1041" /> which is 0.5% of 1.0, on this [[log10|logarithmic]] scale, the solar abundance.<ref>Since 10<sup>−2.29</sup> = 0.00513.</ref> This puts the estimated age range for the cluster at {{nowrap|11 ± 1.5 billion years}}.<ref>{{Cite journal|last1=Di Cecco|first1=A.|last2=Becucci|first2=R.|last3=Bono|first3=G.|last4=Monelli|first4=M.|last5=Stetson|first5=P. B.|last6=Degl'Innocenti|first6=S.|last7=Moroni|first7=P. G. Prada|last8=Nonino|first8=M.|last9=Weiss|first9=A.|last10=Buonanno|first10=R.|last11=Calamida|first11=A.|date=2010-06-27|title=On the absolute age of the Globular Cluster M92|journal=Publications of the Astronomical Society of the Pacific|volume=122|issue=895|pages=991–999|language=en|doi=10.1086/656017|arxiv=1006.5217|bibcode=2010PASP..122..991D |doi-access=free}}</ref>

Its true diameter is 108 ly, and may have a mass corresponding to 330,000 suns.<ref name=":0">{{Cite web |title=Messier Object 92 |url=https://www.messier.seds.org/m/m092.html |access-date=2022-05-28 |website=www.messier.seds.org}}</ref>

The cluster is not yet in, nor guaranteed to undergo, [[core collapse (cluster)|core collapse]] and the core radius figures as about 2&nbsp;[[arcsecond]]s ({{pprime}}).<ref name="aj133_3_1041" /> It is an [[Pieter Oosterhoff|Oosterhoff]] type II (OoII) globular cluster, which means it belongs to the group of metal-poor clusters with longer period [[RR Lyrae variable]] stars. The 1997 ''Catalogue of Variable Stars in Globular Clusters'' listed 28 candidate variable stars in the cluster, although only 20 have been confirmed. As of 2001, there are 17 known RR Lyrae variables in Messier 92.<ref name="aaa369_862" /> 10 X-ray sources have been detected within the 1.02&nbsp;arcminute half-mass radius of the cluster, of which half are candidate [[cataclysmic variable star]]s.<ref name="apj736_2_158" /><ref>{{Cite journal |last1=Ferraro |first1=F. R. |last2=Paltrinieri |first2=B. |last3=Fusi Pecci |first3=F. |last4=Rood |first4=R. T. |last5=Dorman |first5=B. |date=1998-01-01 |title=Faint UV Objects in the Core of Ggcs: a New Subclass of Cvs? |journal=Ultraviolet Astrophysics Beyond the IUE Final Archive |url=https://ui.adsabs.harvard.edu/abs/1998ESASP.413..561F |volume=413 |pages=561|bibcode=1998ESASP.413..561F}}</ref>

M92 is approaching us at 112 km/sec. Its coordinates indicate that the Earth's North [[Celestial pole|Celestial Pole]] periodically passes less than one degree of this cluster during the precession of Earth's axis. Thus, M92 was a "Polarissima Borealis", or "North Cluster", about 12,000 years ago (10,000 BC), and it will again in about 14,000 years (16,000 AD).<ref name=":0" />{{-}}

The multiple stellar populations in this cluster, revealing that it hosts at least two stellar generations of stars named 1G and 2G, as well as two distinct groups of 2G stars (2GA and 2GB).<ref>{{cite news |last1=World |first1=FTT |title=Astronomers discover new insights into multiple stellar populations in Messier 92 using James Webb |url=https://www.followthistrendingworld.com/post/astronomers-discover-new-insights-into-multiple-stellar-populations-in-messier-92-using-james-webb}}</ref> The helium abundances of 2GA and 2GB stars have higher mass fractions than that of the 1G stars by 0.01 and 0.04, respectively.

==Gallery==
<gallery>
M92 arp 750pix.jpg|Messier 92 - wide field view from the [[Isaac Newton Group of Telescopes]]
M92map.png|Map showing how Messier 92 figures in the two-dimensional sky, in the east of Hercules. Maps set by convention against a southern horizon, such that east is left.
Messier92 - SDSS DR14 (panorama).jpg|Messier 92 by the [[Sloan Digital Sky Survey]]
Messier 92 Hubble WikiSky.jpg|Messier 92 by [[Hubble Space Telescope|HST]]; 3.5{{prime}} view
Globular Cluster M92 (NIRCam Image).png|Messier 92 captured by the [[James_Webb_Space_Telescope|James Webb Space Telescope’s]] NIRCam instrument
</gallery>

==See also==
* [[List of Messier objects]]

==References and footnotes==
{{reflist|refs=
<ref name="simbad">{{cite simbad | title=M 92 | access-date=2006-11-17}}</ref>
<ref name="kanas2007">{{citation | first1=Nick | last1=Kanas | title=Star maps: history, artistry, and cartography | series=Springer-Praxis books in popular astronomy | publisher=Springer | year=2007 | isbn=978-0387716688 | page=180 | url=https://books.google.com/books?id=xepttjhzaH8C&pg=PA180}}</ref>
<ref name="garfinckle1997">{{citation | first1=Robert A. | last1=Garfinkle | title=Star-Hopping: Your Visa to Viewing the Universe | publisher=[[Cambridge University Press]] | year=1997 | isbn=978-0521598897 | page=131 | url=https://books.google.com/books?id=40JzBYGREL0C&pg=PA131}}</ref>
<ref name="aj133_3_1041">{{citation | display-authors=1 | last1=Drukier | first1=G. A. | last2=Cohn | first2=H. N. | last3=Lugger | first3=P. M. | last4=Slavin | first4=S. D. | last5=Berrington | first5=R. C. | last6=Murphy | first6=B. W. | title=The Global Kinematics of the Globular Cluster M92 | journal=The Astronomical Journal | volume=133 | issue=3 | pages=1041–1057 |date=March 2007 | doi=10.1086/510721 | bibcode=2007AJ....133.1041D |arxiv = astro-ph/0611246 | s2cid=15452502}}</ref>
<ref name="aaa369_862">{{citation | last1=Kopacki | first1=G. | title=Variable stars in the globular cluster M 92 | journal=Astronomy and Astrophysics | volume=369 | pages=862–870 |year=2003 | doi=10.1051/0004-6361:20010155 | bibcode=2001A&A...369..862K | issue=3 | arxiv=astro-ph/0211042 | s2cid=116811988}}</ref>
<ref name="apj736_2_158">{{citation | display-authors=1 | last1=Lu | first1=Ting-Ni | last2=Kong | first2=Albert K. H. | last3=Verbunt | first3=Frank | last4=Lewin | first4=Walter H. G. | last5=Anderson | first5=Scott F. | last6=Pooley | first6=David | title=Chandra and HST Studies of the X-Ray Sources in Galactic Globular Cluster M92 | journal=The Astrophysical Journal | volume=736 | issue=2 | page=158 |date=August 2011 | doi=10.1088/0004-637X/736/2/158 | bibcode=2011ApJ...736..158L | url=https://dspace.mit.edu/bitstream/1721.1/95659/2/Lu-2011-CHANDRA%20AND%20HST%20STUD.pdf | hdl=1721.1/95659 | s2cid=54766335 | hdl-access=free}}</ref>
<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 [ Erratum: 2011AJ....142...66G ] | 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 |arxiv = 1008.2755 | s2cid=119183070}}</ref>
<ref name="apj721_2_1790">{{citation | last1=Chen | first1=C. W. | last2=Chen | first2=W. P. | title=Morphological Distortion of Galactic Globular Clusters | journal=The Astrophysical Journal | volume=721 | issue=2 | pages=1790–1819 |date=October 2010 | doi=10.1088/0004-637X/721/2/1790 | bibcode=2010ApJ...721.1790C | doi-access=}}</ref>
<ref name="maa">{{citation | first1=Hartmut | last1=Frommert | first2=Christine | last2=Kronberg | title=Messier 92 | date=September 2, 2007 | work=SEDS | publisher=The Munich Astro Archive | url=http://www.maa.clell.de/Messier/E/m092.html | access-date=2012-04-08 | archive-date=2016-03-04 | archive-url=https://web.archive.org/web/20160304031107/http://www.maa.clell.de/Messier/E/m092.html | url-status=dead}}</ref>
<ref name="hcob849_11">{{citation | last1=Shapley | first1=Harlow | last2=Sawyer | first2=Helen B. | title=A Classification of Globular Clusters | journal=Harvard College Observatory Bulletin | issue=849 | pages=11–14 |date=August 1927 | bibcode=1927BHarO.849...11S | postscript=. | volume=849}}</ref>
<ref name="mnras404_3_1203">{{citation | last1=Forbes | first1=Duncan A. | last2=Bridges | first2=Terry | title=Accreted versus in situ Milky Way globular clusters | journal=[[Monthly Notices of the Royal Astronomical Society]] | volume=404 | issue=3 | pages=1203–1214 |date=May 2010 | doi=10.1111/j.1365-2966.2010.16373.x | doi-access=free | bibcode=2010MNRAS.404.1203F | postscript=. |arxiv = 1001.4289 | s2cid=51825384}}</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>
}}
{{notelist}}

==External links==
{{commons category|Messier 92}}
* {{WikiSky}}
* [http://messier.seds.org/m/m092.html Messier 92 @ SEDS Messier pages]
* [http://gclusters.altervista.org/cluster_4.php?ggc=M+92 Messier 92, Galactic Globular Clusters Database page]
* {{cite web|last=Merrifield|first=Michael|title=M92 – Globular Cluster|url=http://www.deepskyvideos.com/videos/messier/M92_globular_cluster.html|work=Deep Sky Videos|publisher=[[Brady Haran]]|author2=Crowther, Paul}}
*{{APOD |date=4 February 2012|title=Comet Garradd and M92}}

{{Sky|17|17|07.27|+|43|08|11.5|26000}}
{{Portal bar|Astronomy|Stars|Outer space}}
{{Messier objects}}
{{Ngc65}}
{{Hercules (constellation)}}

{{DEFAULTSORT:Messier 92}}
[[Category:Globular clusters|Messier 092]]
[[Category:Hercules (constellation)|Messier 092]]
[[Category:Messier objects|092]]
[[Category:NGC objects|Messier 092]]
[[Category:Astronomical objects discovered in 1777]]
[[Category:Discoveries by Johann Elert Bode]]