Editing Messier 70

{{short description|Globular cluster in the constellation Sagittarius}}
{{Use dmy dates|date=March 2019}}
{{Infobox globular cluster
 | name      = [[Messier object|Messier]] 70
 | image     = [[Image:Messier70-HST-Potw1215a.jpg|300px]]
 | caption   = Globular cluster Messier 70 by [[Hubble Space Telescope]]; 3.3{{prime}} view
 | credit    =
 | epoch     = [[J2000]]
 | class     = V<ref name=hcob849_11/>
 | constellation = [[Sagittarius (constellation)|Sagittarius]]
 | ra        = {{RA|18|43|12.76}}<ref name=aj140_6_1830/>
 | dec       = {{DEC|–32|17|31.6}}<ref name="simbad" />
 | dist_ly   = {{Convert|29.4|kly|kpc|abbr=on|lk=on}}<ref name=apj742_1_51/>
 | appmag_v  = 7.9<ref>{{cite web |url=https://messier.seds.org/m/m070.html |title=Messier 70 |access-date=30 April 2022 |website=SEDS Messier Catalog}}</ref>
 | size_v    = {{Val|8.0|ul=arcminute}}<ref name=Adam2018/>
 | mass_msol = {{Val|1.79|e=5}}<ref name=apj742_1_51/>
 | radius_ly = 34&nbsp;ly<ref name=sma/>
 | radius_tidal_arcminsec = {{Val|11.2|u=arcminute}}<ref name=Liller1983/>
 | metal_fe  = –1.35<ref name=mnras404_3_1203/>
 | age       = 12.80&nbsp;[[Gigayear|Gyr]]<ref name=mnras404_3_1203/>
 | notes     = 
 | names     = GCl 101, M70, [[New General Catalogue|NGC]] 6681<ref name="simbad" />
}}

'''Messier 70''' or '''M70''', also known as '''NGC 6681''', is a [[globular cluster]] of stars to be found in the south of [[Sagittarius (constellation)|Sagittarius]].{{efn|On the southernmost line of the main (teapot) asterism; its declination means it will not rise (above the horizon) above the [[58th parallel north]] and will need the observer to be as much as [[43rd parallel north|a further fifteen degrees]] of latitude south for detailed, little distorted observation}} It was discovered by [[Charles Messier]] in 1780.{{efn|on 31 August}}<ref name=Adam2018/> The famous [[comet Hale–Bopp]] was discovered near this cluster in 1995.<ref name=Mobberley2013/>{{efn|on 23 July}} 

It is about 29,400<ref name=apj742_1_51/>&nbsp;[[light year]]s away from [[Earth]] and around {{Convert|2|kpc|ly|order=flip|disp=out}}<ref name=Watson1994/> from the [[Galactic Center]]. It is roughly the same size and [[luminosity]] as its neighbour in space, [[Globular Cluster M69|M69]].<ref name=Hartmut2011/> M70 has a very small core radius of {{Convert|0.068|pc|ly|order=flip|abbr=on|lk=off}}<ref name=Djorgovski1993/> and a half-light radius of {{Convert|55.80|pc|ly|order=flip|abbr=on|lk=off}}.<ref name=Forbes2008/> This cluster has undergone [[Core collapse (cluster)|core collapse]], leaving it centrally concentrated<ref name=Pryor1989/> with the luminosity distribution following a [[power law]].<ref name=Watson1994/>

There are two distinct stellar populations in the cluster, with each displaying unique abundances. These likely represent different generations of stars.<ref name=OMalley2017/> Five known [[variable star]]s lie within its broadest radius, the tidal radius, all of which are [[RR Lyrae variable]]s.<ref name=Liller1983/><ref name=Clement2001/> The cluster may have two [[blue straggler]]s near the core.<ref name=Watson1994/>

==Gallery==
<gallery>
File:Messier 70 Hubble WikiSky.jpg|Image by Hubble Space Telescope
File:M70map.png|Map showing M70, against a conventional (southern) horizon
</gallery>

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

==References and footnotes==
{{reflist|refs=

<ref name=Mobberley2013>{{citation
 | title=It Came From Outer Space Wearing an RAF Blazer!: A Fan's Biography of Sir Patrick Moore
 | first1=Martin | last1=Mobberley
 | publisher=Springer Science & Business Media
 | year=2013 | isbn=978-3319006093 | page=483
 | url=https://books.google.com/books?id=dfO7BAAAQBAJ&pg=PA483 }}</ref>

<ref name=Hartmut2011>{{citation
 | first1=Hartmut | last1=Frommert | first2=Christine | last2=Kronberg
 | title=Globular Cluster M70 | date=30 August 2007 | work=SEDS Messier pages
 | publisher=Students for the Exploration and Development of Space (SEDS)
 | url=http://messier.seds.org/m/m070.html
 | access-date=2018-12-04 | postscript=. }}</ref>

<ref name=Adam2018>{{citation
 | title=Imaging the Messier Objects Remotely from Your Laptop
 | series=The Patrick Moore Practical Astronomy Series
 | first1=Len | last1=Adam | publisher=Springer
 | year=2018 | isbn=978-3319653853 | page=304
 | url=https://books.google.com/books?id=7nNUDwAAQBAJ&pg=PA304 | bibcode=2018imor.book.....A
 }}</ref>

<ref name=Djorgovski1993>{{citation
 | contribution=Physical Parameters of Galactic Globular Clusters
 | last1=Djorgovski | first1=S.
 | title=Structure and Dynamics of Globular Clusters. Proceedings of a Workshop held in Berkeley, California, July 15–17, 1992, to Honor the 65th Birthday of Ivan King
 | editor1-first=S. G. | editor1-last=Djorgovski
 | editor2-first=G. | editor2-last=Meylan
 | publisher=Astronomical Society of the Pacific
 | volume=50 | pages=373 | location=San Francisco, California
 | date=January 1993 | isbn=978-0937707692
 | bibcode=1993ASPC...50..373D | postscript=. }}</ref>

<ref name=Pryor1989>{{citation
 | title=Mass-to-light ratios for globular clusters. I - The centrally concentrated clusters NGC 6624, M28 (NGC 6626), and M70 (NGC 6681)
 | last1=Pryor | first1=Carlton | last2=McClure | first2=Robert D.
 | last3=Fletcher | first3=J. M. | last4=Hesser | first4=James E.
 | display-authors=1 | postscript=.
 | journal=Astronomical Journal
 | volume=98 | date=August 1989 | pages=596–610
 | doi=10.1086/115160 | bibcode=1989AJ.....98..596P }}</ref>

<ref name=Watson1994>{{citation
 | display-authors=1 | postscript=.
 | title=Far-ultraviolet imaging of the globular cluster NGC 6681 with WFPC2
 | last1=Watson | first1=Alan M. | last2=Mould | first2=Jeremy R.
 | last3=Gallagher | first3=John S., III | last4=Ballester | first4=Gilda E.
 | last5=Burrows | first5=Christopher J. | last6=Casertano | first6=Stefano
 | last7=Clarke | first7=John T. | last8=Crisp | first8=David
 | last9=Griffiths | first9=Richard E. | last10=Hester | first10=J. Jeff
 | last11=Hoessel | first11=John G. | last12=Holtzman | first12=Jon A.
 | last13=Scowen | first13=Paul A. | last14=Stapelfeldt | first14=Karl R.
 | last15=Trauger | first15=John T. | last16=Westphal | first16=James A.
 | journal=Astrophysical Journal, Part 2
 | volume=435 | issue=1 | pages=L55–L58 | date=November 1994
 | doi=10.1086/187593 | bibcode=1994ApJ...435L..55W | url=https://authors.library.caltech.edu/53635/1/1994ApJ___435L__55W.pdf
 }}</ref>

<ref name=Liller1983>{{citation
 | title=The variable stars in the field of the globular cluster NGC 6681
 | last1=Liller | first1=M. H.
 | journal=Astronomical Journal | postscript=.
 | volume=88 | date=October 1983 | pages=1463–1469
 | doi=10.1086/113435 | bibcode=1983AJ.....88.1463L }}</ref>

<ref name=Clement2001>{{citation
 | title=Variable Stars in Galactic Globular Clusters
 | last1=Clement | first1=Christine M. | last2=Muzzin | first2=Adam
 | last3=Dufton | first3=Quentin | last4=Ponnampalam | first4=Thivya
 | last5=Wang | first5=John | last6=Burford | first6=Jay
 | last7=Richardson | first7=Alan | last8=Rosebery | first8=Tara
 | last9=Rowe | first9=Jason | last10=Hogg | first10=Helen Sawyer
 | journal=The Astronomical Journal | display-authors=1
 | volume=122 | issue=5 | pages=2587–2599 | date=November 2001
 | doi=10.1086/323719  | arxiv=astro-ph/0108024
 | bibcode=2001AJ....122.2587C | s2cid=38359010 | postscript=. }}</ref>

<ref name=OMalley2017>{{citation
 | title=High-resolution Spectroscopic Abundances of Red Giant Branch Stars in NGC 6681
 | last1=O'Malley | first1=Erin M. | last2=Knaizev | first2=Alexei
 | last3=McWilliam | first3=Andrew | last4=Chaboyer | first4=Brian
 | journal=The Astrophysical Journal | display-authors=1
 | volume=846 | issue=1 | id=23 | pages=15 | date=September 2017
 | doi=10.3847/1538-4357/aa7b72 | postscript=.
 | bibcode=2017ApJ...846...23O | arxiv=1706.06962 | s2cid=118972140 | doi-access=free }}</ref>

<ref name=Forbes2008>{{citation
 | title=Uniting old stellar systems: from globular clusters to giant ellipticals
 | last1=Forbes | first1=Duncan A. | last2=Lasky | first2=Paul
 | last3=Graham | first3=Alister W. | last4=Spitler | first4=Lee
 | display-authors=1
 | journal=Monthly Notices of the Royal Astronomical Society
 | volume=389 | issue=4 | pages=1924–1936 | date=October 2008
 | doi=10.1111/j.1365-2966.2008.13739.x | doi-access=free | postscript=.
 | bibcode=2008MNRAS.389.1924F | arxiv=0806.1090 | s2cid=14108457 }}</ref>

<ref name=aj140_6_1830>{{citation
 | 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
 | display-authors=1 | 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=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=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="simbad">{{cite simbad
 | title=NGC 6681
 | access-date=2006-11-17 }}</ref>

<ref name=apj742_1_51>{{citation
 | 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
 | display-authors=1 | 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=sma>distance × sin( diameter_angle / 2 ) = 34 ly. radius</ref>

}}
{{notelist}}

==External links==
{{Commons category|Messier 70}}
* [http://gclusters.altervista.org/cluster_4.php?ggc=M+70 Messier 70, Galactic Globular Clusters Database page]
* {{WikiSky}}

{{Sky|18|43|12.64|-|32|17|30.8|29300}}
{{Portal bar|Astronomy|Stars|Outer space}}
{{Messier objects}}
{{Ngc70}}

{{DEFAULTSORT:Messier 070}}
[[Category:Globular clusters]]
[[Category:Sagittarius (constellation)]]
[[Category:Messier objects|070]]
[[Category:NGC objects]]
[[Category:Astronomical objects discovered in 1780]]
[[Category:Discoveries by Charles Messier]]