Credits: Jim Misti (Image Acquisition), Aldo Zanetti (Processing)
Astronomical and Imaging Data
| RA: | 16h 47m 14.18s |
| DEC: | -01° 56′ 54.7″ |
| MAG: | 6.70 |
| Diameter: | 16′ |
| Const: | Oph |
| OTA | OGS 32″ RC |
| Focal Length | 6000mm |
| Camera | SBIG STL-11000M |
| Site | Arizona, USA |
| Sky Quality | Bortle 2 |
Useful Informations
NGC 6218, more commonly known as Messier 12 (M12), is a relatively loose and open globular cluster located in the constellation Ophiuchus. It’s an ancient stellar system that is notable for its unusually low density of stars in its core, which has raised questions about its interaction with the Milky Way.
Key Physical Properties
M12 is located approximately 16,400 light-years away from Earth. Its loose structure is a key characteristic, and it is classified as a Shapley-Sawyer Concentration Class IX, indicating a low central concentration of stars. This makes it an interesting contrast to more densely packed clusters.
- 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]≈−1.37 dex), consistent with their formation in the early universe.
- Mass and Structure: With a total mass of about 200,000 solar masses, M12 is one of the less massive globular clusters. Studies have shown that it has lost a significant number of its low-mass stars, which is a strong indicator of tidal stripping—the process where a cluster loses stars due to the gravitational pull of its host galaxy.
Scientific Significance
M12’s sparse nature makes it a valuable object for studying the effects of galactic tides on globular clusters.
- Tidal Stripping: The lack of low-mass stars in M12 suggests that it has passed through the galactic plane multiple times, with the Milky Way’s gravitational forces stripping away its outer stars. This makes M12 a prime example of a cluster in the process of being tidally disrupted.