View source for Astronomy:Messier 56

{{Short description|Globular cluster in the constellation Lyra}}
{{Infobox globular cluster
| | name = [[Astronomy:Messier object|Messier]] 56
| image = [[File:Messier 56 Hubble WikiSky.jpg|250px]]
| caption = Messier 56 by [[Astronomy:Hubble Space Telescope|Hubble Space Telescope]]. 3.6′ view
| credit = 
| epoch = [[Astronomy:J2000|J2000]]
| class = X<ref name=hcob849_11/>
| constellation = Lyra
| ra = {{RA|19|16|35.57}}<ref name=aj140_6_1830/>
| dec = {{DEC|+30|11|00.5}}<ref name=aj140_6_1830/>
| dist_ly = {{Convert|32.9|kly|kpc|abbr=on|lk=on}}<ref name=arXiv2118/>
| appmag_v = 8.3<ref name="seds">{{cite web |url=https://messier.seds.org/m/m056.html |title=Messier 56 |access-date=29 April 2022 |website=SEDS Messier Catalog}}</ref>
| size_v = 8.8'<ref name="seds"/>
| mass_msol = {{Val|2.30|e=5}}<ref name=apj742_1_51/>
| radius_ly = 42&nbsp;ly<ref>From [[Trigonometry|trigonometry]]: radius = {{nowrap|distance × sin( diameter_angle / 2 )}} = {{nowrap|32,900 × sin(8.8′/2)}} = 42.1 ly.</ref>
| v_hb =
| metal_fe = –2.00<ref name=mnras404_3_1203/>
| age = 13.70&nbsp;Gyr<ref name=mnras404_3_1203/>
| notes =
| names = M56, [[Astronomy:New General Catalogue|NGC]] 6779, GCl 110, C 1914+300<ref name="simbad" />
}}
'''Messier 56''' (also known as '''M56''' or '''NGC 6779''') is a [[Astronomy:Globular cluster|globular cluster]] in the [[Astronomy:Constellation|constellation]] [[Astronomy:Lyra|Lyra]].{{efn|Specifically in the center-northwest of Lyra which makes it visible from everywhere above about the 50th parallel south. However the Sun passes through Sagittarius far to the south (or technically the Earth orbits so as to make the Sun seem to do so) throughout December. This also makes the cluster mostly risen during day, not night, in the nearest months but will never impede pre-dawn and post-sunset views from the upper half of northerly latitudes.}} It was discovered by [[Biography:Charles Messier|Charles Messier]] in 1779.{{efn|on January 19}} It is angularly found about midway between [[Astronomy:Albireo|Albireo]] (Beta (β) Cygni) and Sulafat (Gamma (γ) Lyrae). In a [[Astronomy:Light pollution|good night sky]] it is tricky to find with large (50&ndash;80&nbsp;mm) binoculars, appearing as a slightly fuzzy star.<ref name=thompson2007/> The cluster can be resolved using a telescope with an [[Astronomy:Aperture|aperture]] of {{Convert|8|in|cm|abbr=on|sigfig=1}} or larger.<ref name=inglis2004/>

M56 is about 32,900&nbsp;[[Astronomy:Light-year|light-year]]s away from [[Astronomy:Earth|Earth]]<ref name=arXiv2118/> and measures roughly 84&nbsp;light-years across, containing 230,000<ref name=apj742_1_51/> [[Astronomy:Solar mass|solar mass]]es ({{solar mass}}). It is about {{Convert|31|–|32|kly|kpc|abbr=on}} from the [[Galactic Center]] and {{Convert|4.8|kly|kpc|abbr=on}} above the [[Astronomy:Galactic plane|galactic plane]].<ref name=aaa450_1_105/> This cluster has an estimated age of 13.70 billion years and is following a retrograde orbit through the Milky Way. The properties of this cluster suggest that it may have been acquired during the merger of a [[Astronomy:Dwarf galaxy|dwarf galaxy]], of which [[Astronomy:Omega Centauri|Omega Centauri]] forms the surviving nucleus. For Messier 56, the abundance of elements other than hydrogen and helium, what astronomers term the [[Astronomy:Metallicity|metallicity]], has a very low value of [Fe/H] = –2.00 dex which is {{frac|1|100}} of the abundance in the Sun.<ref name=mnras404_3_1203/>

The brightest [[Astronomy:Star|star]]s in M56 are of 13th [[Astronomy:Apparent magnitude|magnitude]], while it contains only about a dozen known [[Astronomy:Variable star|variable star]]s, such as '''V6''' ([[Astronomy:RV Tauri variable|RV Tauri star]]; period: 90 days) or '''V1''' (Cepheid: 1.510 days);<ref name=aa58_121/> other variable stars are V2 (irregular) and V3 (semiregular). In 2000, a diffuse X-ray emission was tentatively identified coming from the vicinity of the cluster. This is most likely [[Astronomy:Interstellar medium|interstellar medium]] that has been heated by the passage of the cluster through the galactic halo. The relative velocity of the cluster is about 177&nbsp;km s<sup>−1</sup>, which is sufficient to heat the medium in its wake to a temperature of 940,000&nbsp;K.<ref name=mnras316_1_L5/>

M56 is part of the [[Astronomy:Gaia Sausage|Gaia Sausage]], the hypothesised remains of a merged dwarf galaxy.<ref>{{cite journal |title=The Sausage Globular Clusters |journal=The Astrophysical Journal |volume=863 |issue=2 |pages=L28 |date=2018 |arxiv=1805.00453|last1=Myeong |first1=G. C |last2=Evans |first2=N. W |last3=Belokurov |first3=V |last4=Sanders |first4=J. L |last5=Koposov |first5=S. E |doi=10.3847/2041-8213/aad7f7 |bibcode=2018ApJ...863L..28M |s2cid=67791285 |doi-access=free }}</ref>

==Gallery==
{{Gallery|width=200
|File:M56HunterWilson.jpg|Messier 56 - wide field view
|File:M56map.png|Map showing location of M56 (Roberto Mura)
}}

==See also==
* [[Astronomy:List of Messier objects|List of Messier objects]]

==References and footnotes==
{{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=mnras404_3_1203>{{citation | last1=Forbes | first1=Duncan A. | last2=Bridges | first2=Terry | title=Accreted versus in situ Milky Way globular clusters | journal=[[Organization:Monthly Notices of the Royal Astronomical Society|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 | bibcode=2010MNRAS.404.1203F |arxiv = 1001.4289 | s2cid=51825384 }}</ref>

<ref name=thompson2007>{{citation | first1=Robert Bruce | last1=Thompson | first2=Barbara Fritchman | last2=Thompson | title=Illustrated guide to astronomical wonders | series=DIY science | publisher=O'Reilly Media, Inc. | date=2007 | isbn=978-0-596-52685-6 | page=311 | url=https://books.google.com/books?id=ymt9nj_uPhwC&pg=PA311 }}</ref>

<ref name=inglis2004>{{citation | first1=Mike | last1=Inglis | title=Astronomy of the Milky Way: Observer's guide to the northern sky | volume=1 | publisher=Springer | date=2004 | isbn=978-1-85233-709-4 | page=90 | url=https://books.google.com/books?id=y4t_-459RPUC&pg=SA2-PA72 | bibcode=2003amwn.book.....I }}</ref>

<ref name=aa58_121>{{citation | display-authors=1 | last1=Pietrukowicz | first1=P. | last2=Olech | first2=A. | last3=Kedzierski | first3=P. | last4=Zloczewski | first4=K. | last5=Wisniewski | first5=M. | last6=Mularczyk | first6=K. | title=CURiuos Variables Experiment (CURVE): Variable Stars in the Metal-Poor Globular Cluster M56 | journal=Acta Astronomica | volume=58 | pages=121–130 |date=June 2008 | bibcode=2008AcA....58..121P |arxiv = 0806.1515 }}</ref>

<ref name=aaa450_1_105>{{citation | display-authors=1 | last1=Bica | first1=E. | last2=Bonatto | first2=C. | last3=Barbuy | first3=B. | last4=Ortolani | first4=S. | title=Globular cluster system and Milky Way properties revisited | journal=Astronomy and Astrophysics | volume=450 | issue=1 | pages=105–115 |date=April 2006 | doi=10.1051/0004-6361:20054351 | bibcode=2006A&A...450..105B |arxiv = astro-ph/0511788 | s2cid=1559058 }}</ref>

<ref name=arXiv2118>{{cite arXiv | display-authors=1 | first1=Valentin D. | last1=Ivanov | first2=Jordanka | last2=Borissova | first3=Almudena | last3=Alonso-Herrero | first4=Tatiana | last4=Russeva | date=2000 | title=Near Infrared Photometry of Galactic Globular Clusters M56 and M15. Extending the Red Giant Branch vs. Metallicity Calibration Towards Metal Poor Systems | eprint=astro-ph/0002118 }}</ref>

<ref name=mnras316_1_L5>{{citation | display-authors=1 | last1=Hopwood | first1=M. E. L. | last2=Evans | first2=A. | last3=Roberts | first3=T. P. | last4=Burleigh | first4=M. R. | last5=Odenkirchen | first5=M. | last6=Beardmore | first6=A. P. | last7=O'brien | first7=T. | last8=Jeffries | first8=R. D. | last9=Penny | first9=A. | title=A possible detection of diffuse extended X-ray emission in the environment of the globular cluster NGC 6779 | journal=Monthly Notices of the Royal Astronomical Society | volume=316 | issue=1 | pages=L5–L8 |date=July 2000 | doi=10.1046/j.1365-8711.2000.03717.x | bibcode=2000MNRAS.316L...5H | doi-access=free }}</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="simbad">{{cite simbad | title=M 56 | access-date=2006-11-16 }}</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>

}}
{{notelist}}

==External links==
* [http://messier.seds.org/m/m056.html Messier 56, SEDS Messier pages]
* [http://gclusters.altervista.org/cluster_4.php?ggc=M+56 Messier 56, Galactic Globular Clusters Database page]
* [http://www.tgdaily.com/space-features/65707-hubble-snaps-a-collection-of-ancient-stars Hubble snaps a collection of ancient stars], August 26, 2012, ''TG Daily''
* {{cite web|title=M56 – Globular Cluster|url=http://www.deepskyvideos.com/videos/messier/M56.html|work=Deep Sky Videos|publisher=[[Biography:Brady Haran|Brady Haran]] |last1=Crowther|first1=Paul| last2=Szymanek|first2=Nik |last3=Merrifield|first3=Mike }}
* {{WikiSky}}

{{Sky|19|16|35.50|+|30|11|04.2|32900}}
{{Messier objects}}
{{catalogs|M=56|NGC=6779}}

[[Category:Globular clusters|Messier 056]]
[[Category:Messier objects|056]]
[[Category:NGC objects|Messier 056]]

{{Sourceattribution|Messier 56}}