Credit: Aldo Zanetti
Astronomical and Imaging Data
| RA: | 21h 29m 58.33s |
| DEC: | +12° 10′ 01.2″ |
| MAG: | 6.20 |
| Diameter: | 18′ |
| Const: | Peg |
| OTA | Celestron 9.25 Edge HD |
| Focal Length | 2350 |
| Camera | ASI1600MM |
| Site | Po Plain, Italy |
| Sky Quality | Bortle 7 |
Useful Informations
NGC 7078, also known as Messier 15 (M15), is a large and highly concentrated globular cluster located in the constellation Pegasus, about 33,600 light-years from Earth. It’s one of the oldest known globular clusters and is particularly famous for having one of the densest cores of any cluster in the Milky Way.
Physical and Chemical Properties
- Structure: M15 is a core-collapsed globular cluster, meaning its core has undergone a gravitational contraction, causing a high density of stars at its center. This results in a bright, unresolved central cusp that appears as a single point of light even with powerful telescopes. Its classification is Shapley-Sawyer Concentration Class IV, indicating a high degree of central concentration.
- Age and Metallicity: With an estimated age of about 12.5 billion years, M15 is a relic from the early universe. Its stars are extremely metal-poor, with a very low abundance of elements heavier than hydrogen and helium, which is characteristic of the first generations of stars.
- Mass and Luminosity: The cluster contains over 100,000 stars and has a total mass estimated at 560,000 times that of the Sun. Its immense luminosity is about 360,000 times that of our Sun, which contributes to its visibility.
Notable Stellar Content and Scientific Significance
The extreme stellar density of M15’s core fosters a dynamic environment for star interactions, leading to the formation of exotic objects.
- Pulsars: M15 hosts a significant population of pulsars (rapidly rotating neutron stars), with at least eight confirmed, including a unique double neutron star system.
- Planetary Nebula: It was the first globular cluster to have a planetary nebula, named Pease 1, discovered within it. This is a rare finding, as these nebulae are typically found in the galactic disk.
- Intermediate-Mass Black Hole: There is strong evidence to suggest the presence of an intermediate-mass black hole at the cluster’s core. While not definitively confirmed, this is a subject of ongoing research and provides a crucial test case for understanding the formation of black holes in dense stellar environments.