# NGC 6522

NGC 6522
Observation data (J2000 epoch)
ConstellationSagittarius
Right ascension18h 03m 34.1s[1]
Declination−30° 02′ 2.3″[1]
Distance25.1 kly (7.7 kpc)[2]
Apparent magnitude (V)8.3[3]
Apparent dimensions (V)16.4'[3]
Physical characteristics
Mass3.00×105[2] M
Metallicity${\displaystyle {\begin{smallmatrix}\left[{\ce {Fe}}/{\ce {H}}\right]\end{smallmatrix}}}$ = –1.34[2] dex
Estimated age12.0 Gyr[4]
Other designationsGCl 82, C 1800-300[1]
See also: Globular cluster, List of globular clusters

NGC 6522 is a globular cluster in the constellation Sagittarius. It is apparent magnitude 8.3, and diameter 16.4 arc minutes, and class VI with stars 16th magnitude and dimmer. It was discovered by William Herschel on June 24, 1784. It is centered in a region of the sky known as Baade's Window.[1][3]

NGC 6522 is possibly the oldest star cluster in the Milky Way,[5] with an age of more than 12 billion years.[6]

## References

1. ^ a b c d "SIMBAD Astronomical Database". Results for NGC 6522. Retrieved 2011-03-13.
2. ^ a b c Boyles, 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.
3. ^ a b c "NGC 6522". Retrieved 2020-09-23.
4. ^ 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
5. ^
6. ^ "The universe's first stars were whirling dervishes", New Scientist by David Shiga, 30 April 2011, p. 20. "Imprints of fast-rotating massive stars in the Galactic Bulge" by Cristina Chiappini et al., Nature 472, pp. 454–457 (28 April 2011).