Credits: Jim Misti (Image Acquisition), Aldo Zanetti (Processing)
Astronomical and Imaging Data
| RA: | 17h 17m 07.39s |
| DEC: | +43° 08′ 09.4″ |
| MAG: | 6.40 |
| Diameter: | 14′ |
| Const: | Her |
| OTA | OGS 32″ RC |
| Focal Length | 6000mm |
| Camera | SBIG STL-11000M |
| Site | Arizona, USA |
| Sky Quality | Bortle 2 |
Useful Informations
NGC 6341, more commonly known as Messier 92 (M92), is one of the oldest, brightest, and most metal-poor globular clusters in the Milky Way’s halo. Located in the constellation Hercules, it is a prime target for research into early stellar populations and the age of the universe.
Key Physical Properties
- Age and Metallicity: M92 is an exceptionally old stellar system, with an estimated age of up to 14.2 billion years. This places its formation shortly after the Big Bang, making it one of the most ancient objects known. Its stars are extremely metal-poor ([Fe/H]≈−2.3 dex), meaning they have a very low abundance of elements heavier than hydrogen and helium. This pristine composition is a direct link to the early universe.
- Structure: The cluster is highly concentrated toward its core, classified as a Shapley-Sawyer Concentration Class IV. It contains several hundred thousand stars densely packed into a diameter of about 110 light-years.
- Location: M92 is located approximately 26,700 light-years from Earth and is situated in the outer galactic halo. It is often overshadowed by its more famous neighbor, Messier 13, but is a scientifically more important object due to its extreme age and chemical composition.
Scientific Significance
M92 serves as a crucial “cosmic fossil” for understanding the earliest stages of galactic formation and stellar evolution.
- Probing the Age of the Universe: Because it is so old, M92 provides a strong lower limit on the age of the universe. Its properties help astronomers refine cosmological models and understand the conditions of the early cosmos.
- Multiple Stellar Populations: Despite its ancient age and low metallicity, M92 has been found to host at least two distinct stellar populations with slightly different chemical compositions. This complex finding challenges the traditional view of globular clusters as single-age, single-metallicity systems. The presence of these multiple populations suggests that the cluster’s stars formed from a gas cloud that was already enriched by a previous generation of stars.
- Variable Stars: The cluster has a low number of variable stars compared to other globular clusters, but it does contain RR Lyrae variables, which are useful for accurately determining the cluster’s distance and are a key area of study for understanding stellar pulsation.