Credit: Aldo Zanetti
Astronomical and Imaging Data
| RA: | 16h 32m 31.86s |
| DEC: | -13° 03′ 13.6″ |
| MAG: | 7.93 |
| Diameter: | 13′ |
| Const: | Oph |
| OTA | Celestron 9.25 Edge HD |
| Focal Length | 2350 |
| Camera | ASI2600MC |
| Site | Central Italy |
| Sky Quality | Bortle 3 |
Useful Informations
NGC 6171, also known as Messier 107 (M107), is a relatively loose and open globular cluster located in the constellation Ophiuchus. It’s a scientifically interesting object because of its low central concentration and a chemical composition that differs slightly from many other globular clusters.
Physical and Chemical Properties
M107 is situated approximately 20,900 light-years from Earth. Its loose structure is its most distinctive feature, and it is classified as a Shapley-Sawyer Concentration Class X. This classification indicates that its stars are not as densely packed toward the center as in many other globular clusters. This provides an excellent opportunity to resolve individual stars and study its stellar populations.
- Age and Metallicity: The cluster is an ancient object, with an estimated age of around 12 billion years. Its stars are moderately metal-poor ([Fe/H]≈−0.99 dex), which is a slightly higher metallicity than the most ancient globulars. This suggests it may have formed from gas that had already been enriched by a previous generation of stars, or that it is a member of a different globular cluster population than the most metal-poor halo clusters.
Scientific Significance
M107’s unique properties make it a valuable target for research.
- Stellar Populations: The cluster stellar population and chemical abundances are a key area of study for understanding the formation and evolution of globular clusters that are not extremely metal-poor.
- Variable Stars: There are 22 known RR Lyrae variable stars in this cluster and a probable SX Phoenicis variable
- Tidal Disruption: Its loose structure and location in the inner galactic halo suggest it may have been subject to tidal stripping—the process where a cluster loses stars due to the gravitational pull of the Milky Way. Its appearance is consistent with a cluster that has lost a significant portion of its original mass.