Credit: Armen Akopian
Astronomical and Imaging Data
| RA: | 18h 03m 34.02s |
| DEC: | -30° 02′ 02.3″ |
| MAG: | 8.27 |
| Diameter: | 9.2′ |
| Const: | Sgr |
| OTA | ASA 20N |
| Focal Length | 1900mm |
| Camera | FLI PL16803 |
| Site | El Sauce, Chile |
| Sky Quality | Bortle 1 |
Useful Informations
NGC 6522 is a globular cluster located in the constellation Sagittarius. It is a scientifically significant object because it resides within a famous region of the sky known as Baade’s Window, a rare, relatively dust-free view of the Galactic bulge.
Physical Properties & Location
- Distance: Located approximately 25,000 light-years from Earth.
- Apparent Magnitude: With an apparent magnitude of 8.27, it is a faint object that requires a medium-sized telescope for observation.
- Concentration: NGC 6522 is a Shapley-Sawyer Concentration Class IV cluster, indicating a moderate degree of central concentration.
- Location in Baade’s Window: The cluster is located in Baade’s Window, a region of the sky with low interstellar dust extinction that offers a clear view of stars in the Galactic bulge. This makes NGC 6522 an excellent tool for studying the properties of the oldest and most metal-poor stellar populations in the inner Milky Way.
Stellar Populations and Metallicity
- Metallicity: NGC 6522 is considered a metal-poor globular cluster, with a metallicity of approximately -1.27 dex. This is unusual for a cluster located so close to the metal-rich Galactic bulge, suggesting it is a very old halo cluster passing through this region.
- RR Lyrae Variable Stars: The cluster contains a population of RR Lyrae variable stars, which are commonly used to determine a cluster’s distance and age. Studies of these stars in NGC 6522 have helped to constrain the properties of the Galactic bulge.