Credit: Armen Akopian
Astronomical and Imaging Data
| RA: | 18h 01m 50.52s |
| DEC: | -08° 57′ 31.6″ |
| MAG: | 10.23 |
| Diameter: | 4.0′ |
| Const: | Oph |
| OTA | Celestron 9.25 Edge HD |
| Focal Length | 1670mm |
| Camera | QHYCCD QHY533 Pro M |
| Site | Rockwood, TX, United States |
| Sky Quality | Bortle 1 |
Useful Informations
NGC 6517 is a globular cluster located in the constellation Ophiuchus. It is a scientifically notable object due to its location in the Galactic bulge, its high metallicity, and the heavy interstellar reddening that makes it a difficult object to study.
Physical Properties & Location
- Distance: Located approximately 23,000 light-years from Earth and about 6,500 light-years from the Galactic Center.
- Apparent Magnitude: With an apparent magnitude of 10.23, it is a very faint object that requires a large amateur telescope to observe.
- Concentration: NGC 6517 is a Shapley-Sawyer Concentration Class III, indicating a highly concentrated core that is not easily resolved.
- Reddening: The cluster is located in a dusty region of the Milky Way, so its light is significantly dimmed and reddened by interstellar dust. This makes it a challenging target for observation and for measuring its true properties.
Stellar Populations and Metallicity
- Metallicity: NGC 6517 is considered a metal-rich globular cluster, with a metallicity of approximately -1.2 dex. This is typical for globular clusters located in the Milky Way’s bulge.
- Multiple Populations: Spectroscopic and photometric studies have revealed that NGC 6517 contains at least two distinct stellar populations with varying chemical compositions, particularly in the abundance of light elements like sodium.
- RR Lyrae Stars: Despite its high metallicity, NGC 6517 has a population of RR Lyrae variable stars, which are typically found in metal-poor clusters. This makes the cluster a key object for studying the relationship between a globular cluster’s metallicity and the presence of these variable stars.