View source for NGC 6522

{{Short description|Globular cluster in the constellation of Sagittarius}}
{{Infobox globular cluster
| name      = [[New General Catalogue|NGC]] 6522
| image     = [[File:NGC 6522 ACS 435 658 Wiki.jpg|250px]]
| caption   =
| epoch     = [[J2000]]
| class     = VI{{cn|date=September 2024}}
| constellation = [[Sagittarius (constellation)|Sagittarius]]
| ra        = {{RA|18|03|34.08}}<ref name=Di_Criscienzo_et_al_2006/>
| dec       = {{DEC|−30|02|02.3}}<ref name=Di_Criscienzo_et_al_2006/>
| dist_ly   = {{Convert|25.1|kly|kpc|abbr=on|lk=on}}<ref name=apj742_1_51/>
| appmag_v  = 8.3<ref name=O'Meara_2013/>
| absmag_v  = −7.67<ref name=Di_Criscienzo_et_al_2006/>
| size_v    = {{val|9.4|ul=arcminute}}<ref name=O'Meara_2013/>
| mass_msol = {{Val|5.93|e=4}}<ref name="Fernández-Trincado_et_al_2019"/>
| radius_ly =
| metal_fe  = –1.34<ref name=apj742_1_51/>
| v_hb      =
| age       = 12.0&nbsp;[[Gigayear|Gyr]]<ref name=mnras385_4_1998/>
| notes     =
| names     = {{odlist|name=GCl 82|name2=C 1800-300}}<ref name=simbad/>
}}
'''NGC 6522''' is a [[globular cluster]] of stars in the southern [[constellation]] of [[Sagittarius (constellation)|Sagittarius]]. It was discovered by German-British astronomer [[William Herschel]] on June 24, 1784. The cluster has an [[apparent visual magnitude]] of 8.3 and an [[angular diameter]] of {{val|9.4|u=arcminute}}.<ref name=O'Meara_2013/> It is located at a distance of {{Convert|25.1|kly|kpc|abbr=on|lk=on}} from the Sun,<ref name=apj742_1_51/> and lies in the [[Galactic bulge|Milky Way's central bulge]],<ref name=Ness_et_al_2014/> about {{cvt|0.6|kpc|kly|order=flip}} from the [[Galactic Center]].<ref name=Di_Criscienzo_et_al_2006/> The cluster is centered in a region of the sky known as [[Baade's Window]].<ref name="seds" /> It is highly impacted by [[Extinction (astronomy)|reddening]] due to [[interstellar dust]] and the view is heavily contaminated by [[field star]]s, making it more difficult identify members.<ref name=Arellano_Ferro_2023/>
NGC 6522 is possibly the oldest star cluster in the [[Milky Way]],<ref name=Barbuy_et_al_2009/> with an age of more than 12 billion years.<ref name=Shiga_2011/><ref name=Chiappini_2011/> It is a [[Core collapse (cluster)|core collapsed cluster]] with a [[core radius]] of {{val|0.5|u=arcminute}} and a {{val|1.0|u=arcminute}} half-light radius.<ref name=Arellano_Ferro_2023/> The cluster formed four billion years before the Milky Way galactic bar appeared, and may have been confined to the bar for a period of time. At present it trails the bar in its orbit around the core.<ref name=Barbuy_et_al_2021/>
This is a low mass globular cluster with an estimated {{Val|5.93|e=4}} times the [[mass of the Sun]]. Distinctive chemical abundances among the members indicate the cluster has multiple populations of stars, with the younger populations exhibiting pollution from earlier generations.<ref name="Fernández-Trincado_et_al_2019"/> Twenty [[variable star]]s have been identified as members of NGC 6522, consisting of eight [[RR Lyrae variable|RR Lyrae]], three [[type II Cepheid]]s, and nine [[long-period variable star]]s.<ref name=Arellano_Ferro_2023/> Six [[pulsar]]s have been discovered.<ref name=Abbate_et_al_2023/>
==Gallery==
<gallery>
N6522 32ins.jpg|The globular clusters [[NGC 6528]] (lower left) is close to NGC 6522 (upper right)
HST SWEEPS Galaxy Location-2006.jpg|The cluster is located in [[Baade's Window]], a region of night sky that is not clouded by dust from the [[Milky Way]].
</gallery>
==References==
{{reflist|refs=
* [[Robert Burnham, Jr]], ''Burnham's Celestial Handbook: An obsever's guide to the universe beyond the solar system'', vol 3, p.1555
<ref name=O'Meara_2013>{{cite book
| title=Deep-Sky Companions: Southern Gems
| first=Stephen James | last=O'Meara
| page=367 | year=2013 | isbn=9781107015012
| publisher=Cambridge University Press
| url=https://books.google.com/books?id=S5QIEKns33sC&pg=367 }}</ref>
<ref name=apj742_1_51>{{cite journal
| title=Young Radio Pulsars in Galactic Globular Clusters
| 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.
| 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
| arxiv=1108.4402 | s2cid=118649860 }}</ref>
<ref name=mnras385_4_1998>{{cite journal
| title=Spectroscopic ages and metallicities of stellar populations: validation of full spectrum fitting
| display-authors=1 | last1=Koleva | first1=M.
| last2=Prugniel | first2=Ph. | last3=Ocvirk | first3=P.
| last4=Le Borgne | first4=D. | last5=Soubiran | first5=C.
| journal=[[Monthly Notices of the Royal Astronomical Society]]
| volume=385 | issue=4 | pages=1998–2010 |date=April 2008
| doi=10.1111/j.1365-2966.2008.12908.x | doi-access=free | s2cid=17571531
| bibcode=2008MNRAS.385.1998K | arxiv=0801.0871 }}</ref>
<ref name=Barbuy_et_al_2009>{{cite journal
| title=VLT-FLAMES Analysis of 8 giants in the Bulge Metal-poor Globular Cluster NGC 6522: Oldest Cluster in the Galaxy?
| last1=Barbuy | first1=B. | last2=Zoccali | first2=M.
| last3=Ortolani | first3=S. | last4=Hill | first4=V.
| last5=Minniti | first5=D. | last6=Bica | first6=E.
| last7=Renzini | first7=A. | last8=Gómez | first8=A.
| display-authors=1 | journal=Astronomy and Astrophysics
| volume=507 | issue=1 | pages=405–415 | date=November 2009
| doi=10.1051/0004-6361/200912748
| bibcode=2009A&A...507..405B | arxiv=0908.3603 }}</ref>
<ref name=Di_Criscienzo_et_al_2006>{{cite journal | display-authors=1
| title=RR Lyrae-based calibration of the Globular Cluster Luminosity Function
| last1=Di Criscienzo | first1=M. | last2=Caputo | first2=F.
| last3=Marconi | first3=M. | last4=Musella | first4=I.
| journal=Monthly Notices of the Royal Astronomical Society
| volume=365 | issue=4 | pages=1357–1366 | date=February 2006
| doi=10.1111/j.1365-2966.2005.09819.x | doi-access=free | s2cid=17838243
| bibcode=2006MNRAS.365.1357D | arxiv=astro-ph/0511128 }}</ref>
<ref name=Ness_et_al_2014>{{cite journal
| title=NGC 6522: a typical globular cluster in the Galactic bulge without signatures of rapidly rotating Population III stars
| display-authors=1 | last1=Ness | first1=Melissa
| last2=Asplund | first2=Martin | last3=Casey | first3=Andrew R.
| journal=Monthly Notices of the Royal Astronomical Society
| volume=445 | issue=3 | pages=2994−2998 | date=December 2014
| doi=10.1093/mnras/stu2144 | doi-access=free | arxiv=1408.0290
| bibcode=2014MNRAS.445.2994N }}</ref>
<ref name="Fernández-Trincado_et_al_2019">{{cite journal
| title=H-band discovery of additional second-generation stars in the Galactic bulge globular cluster NGC 6522 as observed by APOGEE and Gaia
| last1=Fernández-Trincado | first1=J. G. | last2=Zamora | first2=O.
| last3=Souto | first3=Diogo | last4=Cohen | first4=R. E.
| last5=Dell'Agli | first5=F. | last6=García-Hernández | first6=D. A.
| last7=Masseron | first7=T. | last8=Schiavon | first8=R. P.
| last9=Mészáros | first9=Sz. | last10=Cunha | first10=K.
| last11=Hasselquist | first11=S. | last12=Shetrone | first12=M.
| last13=Schiappacasse Ulloa | first13=J. | last14=Tang | first14=B.
| last15=Geisler | first15=D. | last16=Schleicher | first16=D. R. G.
| last17=Villanova | first17=S. | last18=Mennickent | first18=R. E.
| last19=Minniti | first19=D. | last20=Alonso-García | first20=J.
| last21=Manchado | first21=A. | last22=Beers | first22=T. C.
| last23=Sobeck | first23=J. | last24=Zasowski | first24=G.
| last25=Schultheis | first25=M. | last26=Majewski | first26=S. R.
| last27=Rojas-Arriagada | first27=A. | last28=Almeida | first28=A.
| last29=Santana | first29=F. | last30=Oelkers | first30=R. J.
| last31=Longa-Peña | first31=P. | last32=Carrera | first32=R.
| last33=Burgasser | first33=A. J. | last34=Lane | first34=R. R.
| last35=Roman-Lopes | first35=A. | last36=Ivans | first36=I. I.
| last37=Hearty | first37=F. R. | display-authors=1
| journal=Astronomy & Astrophysics
| volume=627 | at=id. A178 | date=July 2019
| doi=10.1051/0004-6361/201834391 | arxiv=1801.07136
| bibcode=2019A&A...627A.178F }}</ref>
<ref name=Arellano_Ferro_2023>{{cite journal
| title=Variable stars in the field of the Galactic bulge globular cluster NGC 6522
| last1=Arellano Ferro | first1=A. | last2=Prudil | first2=Z.
| last3=Yepez | first3=M. A. | last4=Bustos Fierro | first4=I.
| last5=Luna | first5=A. | display-authors=1
| journal=Astrophysics and Space Science
| volume=368 | issue=10 | at=id. 91 | date=October 2023
| doi=10.1007/s10509-023-04249-4 | arxiv=2310.16257
| bibcode=2023Ap&SS.368...91A }}</ref>
<ref name=Abbate_et_al_2023>{{cite journal
| title=A MeerKAT view of the pulsars in the globular cluster NGC 6522
| last1=Abbate | first1=F. | last2=Ridolfi | first2=A.
| last3=Freire | first3=P. C. C. | last4=Padmanabh | first4=P. V.
| last5=Balakrishnan | first5=V. | last6=Buchner | first6=S.
| last7=Zhang | first7=L. | last8=Kramer | first8=M.
| last9=Stappers | first9=B. W. | last10=Barr | first10=E. D.
| last11=Chen | first11=W. | last12=Champion | first12=D.
| last13=Ransom | first13=S. | last14=Possenti | first14=A.
| display-authors=1 | journal=Astronomy & Astrophysics
| volume=680 | at=id. A47 | date=December 2023
| doi=10.1051/0004-6361/202347725 | arxiv=2310.03800
| bibcode=2023A&A...680A..47A }}</ref>
<ref name=Barbuy_et_al_2021>{{cite journal
| title=UVES analysis of red giants in the bulge globular cluster NGC 6522
| last1=Barbuy | first1=B. | last2=Cantelli | first2=E.
| last3=Muniz | first3=L. | last4=Souza | first4=S. O.
| last5=Chiappini | first5=C. | last6=Hirschi | first6=R.
| last7=Cescutti | first7=G. | last8=Pignatari | first8=M.
| last9=Ortolani | first9=S. | last10=Kerber | first10=L.
| last11=Maia | first11=F. F. S. | last12=Bica | first12=E.
| last13=Depagne | first13=E. | display-authors=1
| journal=Astronomy & Astrophysics
| volume=654 | at=id. A29 | date=October 2021
| doi=10.1051/0004-6361/202140815 | arxiv=2107.08746
| bibcode=2021A&A...654A..29B }}</ref>
<ref name="seds">{{cite web
| title=NGC 6522
| work=Students for the Exploration and Development of Space
| url=http://spider.seds.org/spider/MWGC/n6522.html
| access-date=2020-09-23}}</ref>
<ref name="simbad">{{cite web
| title=SIMBAD Astronomical Database
| work=Results for NGC 6522
| url=http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=NGC+6522
| access-date=2011-03-13}}</ref>
<ref name=Shiga_2011>{{cite journal
| title=The universe's first stars were whirling dervishes
| first=David | last=Shiga
| journal=[[New Scientist]]
| date=30 April 2011 | page=20
| url=https://www.newscientist.com/article/dn20426-the-universes-first-stars-were-whirling-dervishes.html
| access-date=2024-09-09 }}</ref>
<ref name=Chiappini_2011>{{cite journal
| title=Imprints of fast-rotating massive stars in the Galactic Bulge
| first1=Cristina | last1=Chiappini | last2=Frischknecht | first2=Urs
| last3=Meynet | first3=Georges | last4=Hirschi | first4=Raphael
| last5=Barbuy | first5=Beatriz | last6=Pignatari | first6=Marco
| last7=Decressin | first7=Thibaut | last8=Maeder | first8=André
| display-authors=1 | journal=Nature
| volume=472 | pages=454–457 | date=28 April 2011
| issue=7344 | doi=10.1038/nature10000 | pmid=21525928 | bibcode=2011Natur.472..454C }}</ref>
}}
==External links==
*{{commons category-inline}}
*[http://gclusters.altervista.org/cluster_4.php?ggc=NGC+6522 NGC6522, Galactic Globular Clusters Database page]
{{Ngc70}}
[[Category:Globular clusters]]
[[Category:Sagittarius (constellation)]]
[[Category:NGC objects|6522]]