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NGC 6522

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NGC6522
Observation data (J2000epoch)
ClassVI[citation needed]
ConstellationSagittarius
Right ascension18h03m34.08s[1]
Declination−30° 02′ 02.3″[1]
Distance25.1kly(7.7kpc)[2]
Apparent magnitude(V)8.3[3]
Apparent dimensions(V)9.4′[3]
Physical characteristics
Absolute magnitude−7.67[1]
Mass5.93×104[4]M☉
Metallicity= –1.34[2]dex
Estimated age12.0Gyr[5]
Other designationsGCl 82, C 1800-300[6]
See also:Globular cluster,List of globular clusters

NGC 6522is aglobular clusterof stars in the southernconstellationofSagittarius.It was discovered by German-British astronomerWilliam Herschelon June 24, 1784. The cluster has anapparent visual magnitudeof 8.3 and anangular diameterof9.4′.[3]It is located at a distance of 25.1kly(7.7kpc) from the Sun,[2]and lies in theMilky Way's central bulge,[7]about 2.0 kly (0.6 kpc) from theGalactic Center.[1]The cluster is centered in a region of the sky known asBaade's Window.[8]It is highly impacted byreddeningdue tointerstellar dustand the view is heavily contaminated byfield stars,making it more difficult identify members.[9]

NGC 6522 is possibly the oldest star cluster in theMilky Way,[10]with an age of more than 12 billion years.[11][12]It is acore collapsed clusterwith acore radiusof0.5′and a1.0′half-light radius.[9]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.[13]

This is a low mass globular cluster with an estimated5.93×104times themass 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.[4]Twentyvariable starshave been identified as members of NGC 6522, consisting of eightRR Lyrae,threetype II Cepheids,and ninelong-period variable stars.[9]Sixpulsarshave been discovered.[14]

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  • The globular clusters NGC 6528 (lower left) is close to NGC 6522 (upper right)
    The globular clustersNGC 6528(lower left) is close to NGC 6522 (upper right)
  • The cluster is located in Baade's Window, a region of night sky that is not clouded by dust from the Milky Way.
    The cluster is located inBaade's Window,a region of night sky that is not clouded by dust from theMilky Way.

References

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  1. ^abcdDi Criscienzo, M.; et al. (February 2006)."RR Lyrae-based calibration of the Globular Cluster Luminosity Function".Monthly Notices of the Royal Astronomical Society.365(4): 1357–1366.arXiv:astro-ph/0511128.Bibcode:2006MNRAS.365.1357D.doi:10.1111/j.1365-2966.2005.09819.x.S2CID17838243.
  2. ^abcBoyles, J.; et al. (November 2011). "Young Radio Pulsars in Galactic Globular Clusters".The Astrophysical Journal.742(1): 51.arXiv:1108.4402.Bibcode:2011ApJ...742...51B.doi:10.1088/0004-637X/742/1/51.S2CID118649860.
  3. ^abcO'Meara, Stephen James (2013).Deep-Sky Companions: Southern Gems.Cambridge University Press. p. 367.ISBN9781107015012.
  4. ^abFernández-Trincado, J. G.; et al. (July 2019). "H-band discovery of additional second-generation stars in the Galactic bulge globular cluster NGC 6522 as observed by APOGEE and Gaia".Astronomy & Astrophysics.627.id. A178.arXiv:1801.07136.Bibcode:2019A&A...627A.178F.doi:10.1051/0004-6361/201834391.
  5. ^Koleva, M.; et al. (April 2008)."Spectroscopic ages and metallicities of stellar populations: validation of full spectrum fitting".Monthly Notices of the Royal Astronomical Society.385(4): 1998–2010.arXiv:0801.0871.Bibcode:2008MNRAS.385.1998K.doi:10.1111/j.1365-2966.2008.12908.x.S2CID17571531.
  6. ^"SIMBAD Astronomical Database".Results for NGC 6522.Retrieved2011-03-13.
  7. ^Ness, Melissa; et al. (December 2014)."NGC 6522: a typical globular cluster in the Galactic bulge without signatures of rapidly rotating Population III stars".Monthly Notices of the Royal Astronomical Society.445(3): 2994−2998.arXiv:1408.0290.Bibcode:2014MNRAS.445.2994N.doi:10.1093/mnras/stu2144.
  8. ^"NGC 6522".Students for the Exploration and Development of Space.Retrieved2020-09-23.
  9. ^abcArellano Ferro, A.; et al. (October 2023). "Variable stars in the field of the Galactic bulge globular cluster NGC 6522".Astrophysics and Space Science.368(10). id. 91.arXiv:2310.16257.Bibcode:2023Ap&SS.368...91A.doi:10.1007/s10509-023-04249-4.
  10. ^Barbuy, B.; et al. (November 2009). "VLT-FLAMES Analysis of 8 giants in the Bulge Metal-poor Globular Cluster NGC 6522: Oldest Cluster in the Galaxy?".Astronomy and Astrophysics.507(1): 405–415.arXiv:0908.3603.Bibcode:2009A&A...507..405B.doi:10.1051/0004-6361/200912748.
  11. ^Shiga, David (30 April 2011)."The universe's first stars were whirling dervishes".New Scientist:20.Retrieved2024-09-09.
  12. ^Chiappini, Cristina; et al. (28 April 2011). "Imprints of fast-rotating massive stars in the Galactic Bulge".Nature.472(7344): 454–457.Bibcode:2011Natur.472..454C.doi:10.1038/nature10000.PMID21525928.
  13. ^Barbuy, B.; et al. (October 2021). "UVES analysis of red giants in the bulge globular cluster NGC 6522".Astronomy & Astrophysics.654.id. A29.arXiv:2107.08746.Bibcode:2021A&A...654A..29B.doi:10.1051/0004-6361/202140815.
  14. ^Abbate, F.; et al. (December 2023). "A MeerKAT view of the pulsars in the globular cluster NGC 6522".Astronomy & Astrophysics.680.id. A47.arXiv:2310.03800.Bibcode:2023A&A...680A..47A.doi:10.1051/0004-6361/202347725.
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