Credit: Armen Akopian
Astronomical and Imaging Data
| RA: | 13h 46m 26.81s |
| DEC: | -51° 22′ 27.3″ |
| MAG: | 7.34 |
| Diameter: | 11.0′ |
| Const: | Cen |
| OTA | Planewave CDK 24″ |
| Focal Length | 3974mm |
| Camera | QHYCCD QHY600 M |
| Site | El Sauce, Chile |
| Sky Quality | Bortle 1 |
Useful Informations
NGC 5286 is a globular cluster located in the constellation Centaurus, also known as Caldwell 84. While it’s relatively faint and small, its stellar and kinematic properties have made it an important subject for understanding the complex origins of globular clusters and the Milky Way’s halo.
Physical Properties & Dynamics
- Distance: NGC 5286 is located approximately 35,900 light-years from Earth.
- Mass and Age: It’s a massive cluster, with an estimated mass of about 7.13 × 105 solar masses, and is one of the oldest known, with an age of around 12.5 billion years.
- Concentration: The cluster has a Shapley-Sawyer Concentration Class of V, indicating a moderate stellar concentration.
- Tidal Disruption: Recent research suggests that NGC 5286 is part of the Gaia Sausage, the hypothesized remnant of a dwarf galaxy that merged with the Milky Way billions of years ago. This origin is supported by its highly eccentric orbit and its association with a tidal stream of stars.
Stellar Populations
NGC 5286 is a classic example of a globular cluster with multiple stellar populations, which is a significant departure from the traditional view of these objects as “simple stellar populations” with a single generation of stars.
- Chemical Variations: Observations have revealed that stars within the cluster have variations in their abundance of both light elements (like nitrogen and sodium) and heavier s-process elements (produced by slow neutron capture). This is a very rare and “anomalous” feature among globular clusters.
- Oosterhoff Type II: Based on the properties of its RR Lyrae variable stars, NGC 5286 is classified as an Oosterhoff Type II cluster. This is unusual given its relatively high metallicity for this class, making it an interesting object for studying the relationship between a cluster’s chemistry and its stellar populations.
- Intermediate-Mass Black Hole (IMBH): Kinematic studies of the cluster’s core have provided tentative evidence for the presence of an intermediate-mass black hole with a mass of up to 6,000 solar masses, though this remains an area of active research.