# NGC 6522

NGC 6522
32 inch telescope
NGC 6528 (lower left) and NGC 6522 (upper right)
Observation data (J2000 epoch)
Constellation Sagittarius
Right ascension 18h 3m 34.1s[1]
Declination −30° 2′ 2.3″[1]
Distance 25.1 kly (7.7 kpc)[2]
Apparent magnitude (V) 10.5
Apparent dimensions (V) 2'
Physical characteristics
Mass 3.00×105[2] M
Metallicity ${\displaystyle {\begin{smallmatrix}\left[{\ce {Fe}}/{\ce {H}}\right]\end{smallmatrix}}}$ = –1.34[2] dex
Estimated age 12.0 Gyr[3]

NGC 6522 is a globular cluster in the constellation Sagittarius. It is apparent magnitude 10.5, and diameter 2 arc seconds, 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]

Globular cluster NGC 6522, by HST.

NGC 6522 is possibly the oldest star cluster in the Milky Way,[4] with an age of more than 12 billion years.[5]

## References

1. ^ a b c "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, Bibcode:2011ApJ...742...51B, arXiv:, doi:10.1088/0004-637X/742/1/51.
3. ^ 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, Bibcode:2008MNRAS.385.1998K, arXiv:, doi:10.1111/j.1365-2966.2008.12908.x
4. ^
5. ^ "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).