View source for Messier 12

{{short description|Globular cluster in the constellation Ophiuchus}}
{{ Infobox globular cluster
| name=Messier 12
| image=[[Image:M12 Adam Block.jpg|300px]]
| caption=Globular cluster Messier 12 in Ophiuchus
| credit=
| epoch=[[J2000]]
| class=IX<ref name=hcob849_11/>
| constellation=[[Ophiuchus]]
| ra={{RA|16|47|14.18}}<ref name=aj140_6_1830/>
| dec={{DEC|–01|56|54.7}}<ref name=aj140_6_1830/>
| dist_ly={{cvt|5.04|±|0.05|kpc|kly|order=flip|lk=on}}<ref name=Gontcharov/>
| appmag_v=6.7<ref>{{cite web |url=http://www.messier.seds.org/m/m012.html |title=Messier 12 |access-date=21 July 2024 |website=SEDS Messier Catalog}}</ref>
| size_v=16.0{{prime}}
| mass_msol={{Val|8.7|e=4}}<ref name=mnras406_3_2000/>
| radius_ly=37.2&nbsp;ly<ref group=NB>distance × sin( diameter_angle / 2 ) = 37.2 ly radius</ref>
| v_hb=
| metal_fe = –1.14<ref name=mnras404_3_1203/>
| age = 13.8 ± 1.1&nbsp;[[Gigayear|Gyr]]<ref name=Gontcharov/>
| notes=
| names=[[New General Catalogue|NGC]] 6218<ref name="simbad" />
}}

'''Messier 12''' or '''M 12''' (also designated '''NGC 6218''') is a [[globular cluster]] in the [[constellation]] of [[Ophiuchus]]. It was discovered by the French astronomer [[Charles Messier]] on May 30, 1764, who described it as a "nebula without stars".<ref name=thompson_thompson2007/> In dark conditions this cluster can be faintly seen with a pair of binoculars. Resolving the stellar components requires a telescope with an [[aperture]] of {{Convert|8|in|cm|abbr=on}} or greater.<ref name=monks2010/> In a {{Convert|10|in|cm|abbr=on}} scope, the granular core shows a diameter of 3{{prime}} ([[arcminute]]s) surrounded by a 10{{prime}} halo of stars.<ref name=thompson_thompson2007/>

M12 is roughly 3°<ref name=monks2010/> northwest from the cluster [[Messier 10|M10]] and 5.6° [[boxing the compass|east southeast]] from star [[Lambda Ophiuchi]]. It is also located near the 6th magnitude [[12 Ophiuchi]].<ref name=OMeara1998 /> The cluster is about {{Convert|16400|ly|pc|abbr=off}}<ref name=Gontcharov/> from [[Earth]] and has a spatial diameter of about 75 light-years. The brightest stars of M12 are of 12th [[apparent magnitude|magnitude]]. M10 and M12 are only a few thousand light-years away from each other and each cluster would appear at about magnitude 4.5 from the other.<ref name=OMeara1998 /> With a Shapley-Sawyer rating of IX,<ref name=hcob849_11/> it is rather loosely packed for a globular and was once thought to be a tightly concentrated [[open cluster]]. Thirteen [[variable star]]s have been recorded in this cluster. M12 is approaching us at a velocity of 16&nbsp;km/s.<ref>{{Cite web|title = Messier 12: Gumball Globular {{!}} Messier Objects|url = http://www.messier-objects.com/messier-12-gumball-globular/|website = www.messier-objects.com| date=11 March 2015 |access-date = 2015-08-17}}</ref>

A study published in 2006 concluded that this cluster has an unusually low number of low-mass stars. The authors surmise that they were stripped from the cluster by passage through the relatively matter-rich plane of the [[Milky Way]].<ref name=eso2006/>

<gallery>
Image:M12 Hubble.jpg|Messier 12 core by [[Hubble Space Telescope|HST]]
Image:ESO-Messier 12-Phot-04a-06.jpg| The Central Part of Messier 12. Credit: [[ESO]]
Image:M12map.png|Map showing the location of M12
</gallery>

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

==Notes==
{{reflist|group=NB}}

==References==
{{reflist|refs=

<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 | volume=849 | issue=849 | pages=11–14 |date=August 1927 | bibcode=1927BHarO.849...11S | postscript=. }}</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 | 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=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>

<ref name="simbad">{{cite simbad | title=M 12 | access-date=2006-11-15 }}</ref>

<ref name=monks2010>{{citation | first1=Neale | last1=Monks | series=Patrick Moore's Practical Astronomy Series | title=Go-To Telescopes Under Suburban Skies | publisher=Springer | year=2010 | isbn=978-1441968500 | page=118 | url=https://books.google.com/books?id=waO6tUtfblsC&pg=PA118 | postscript=. }}</ref>

<ref name=eso2006>{{citation | publisher=[[ESO]] | url=http://www.eso.org/outreach/press-rel/pr-2006/pr-04-06.html | title=How to Steal a Million Stars? | date=February 7, 2006 | postscript=. | url-status=dead | archive-url=https://web.archive.org/web/20070208073129/http://www.eso.org/outreach/press-rel/pr-2006/pr-04-06.html | archive-date=February 8, 2007 }}</ref>

<ref name=thompson_thompson2007>{{citation | first1=Robert Bruce | last1=Thompson | first2=Barbara Fritchman | last2=Thompson | title=Illustrated guide to astronomical wonders | series=DIY science O'Reilly Series | publisher=[[O'Reilly Media, Inc.]] | year=2007 | isbn=978-0596526856 | page=137 | url=https://books.google.com/books?id=ymt9nj_uPhwC&pg=PA137 | postscript=. }}</ref>

<ref name=Gontcharov>{{cite journal | doi=10.1093/mnras/stab2756 | title=Isochrone fitting of Galactic globular clusters – III. NGC 288, NGC 362, and NGC 6218 (M12) | year=2021 | last1=Gontcharov | first1=George A. | last2=Khovritchev | first2=Maxim Yu | last3=Mosenkov | first3=Aleksandr V. | last4=Il'In | first4=Vladimir B. | last5=Marchuk | first5=Alexander A. | last6=Savchenko | first6=Sergey S. | last7=Smirnov | first7=Anton A. | last8=Usachev | first8=Pavel A. | last9=Poliakov | first9=Denis M. | journal=Monthly Notices of the Royal Astronomical Society | volume=508 | issue=2 | pages=2688–2705| doi-access=free | arxiv=2109.13115 }}</ref>

<ref name=OMeara1998>{{citation
 | title=Deep-Sky Companions: The Messier Objects
 | first1=Stephen James | last1=O'Meara | first2=David H. | last2=Levy 
 | publisher=Cambridge University Press | postscript=.
 | year=1998 | isbn=978-0521553322 | page=68
 | url=https://books.google.com/books?id=jis4evHuuzUC&pg=PA68 }}</ref>

}}

==External links==
{{commons}}
*[http://www.messier.seds.org/m/m012.html Messier 12, SEDS Messier pages]
*[http://gclusters.altervista.org/cluster_4.php?ggc=M+12 Messier 12, Galactic Globular Clusters Database page]
*[http://www.universetoday.com/am/publish/past_globular_m12.html?822006 'Stolen' stars article at ''Universe Today'']
*[http://www.astrovox.gr/forum/album_pic.php?pic_id=18281 Messier 12, Amateur astrophotographer (hgg) with a Celestron 9.25"]
*{{WikiSky}}

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{{Messier objects}}
{{Ngc65}}
{{Sky|16|47|14.52|-|01|56|52.1|160000}}

{{DEFAULTSORT:Messier 012}}
[[Category:Globular clusters]]
[[Category:Ophiuchus]]
[[Category:Messier objects|012]]
[[Category:NGC objects]]
[[Category:Astronomical objects discovered in 1764|17640530]]
[[Category:Discoveries by Charles Messier]]