Credit: Aldo Zanetti
Astronomical and Imaging Data
| RA: | 05h 24m 11.09s |
| DEC: | -24° 31′ 29.0″ |
| MAG: | 7.73 |
| Diameter: | 9.6′ |
| Const: | Lep |
| OTA | Celestron 9.25 Edge HD |
| Focal Length | 2350 |
| Camera | ASI2600MC |
| Site | Central Italy |
| Sky Quality | Bortle 3 |
Useful Informations
NGC 1904, also known as Messier 79 (M79), is a globular cluster in the constellation Lepus. It’s a key object for studying stellar evolution and galactic dynamics due to its unusual location and chemical properties.
Key Properties and Structure
M79 is located approximately 41,000 light-years from Earth, but more significantly, it’s roughly 60,000 light-years from the center of the Milky Way. Its position is unusual as it lies on the side of the sky opposite to the galactic center. This has led to the hypothesis that it may not be a native globular cluster of the Milky Way, but rather a remnant of a dwarf galaxy that our galaxy is in the process of absorbing. It is estimated to be about 11.7 billion years old.
Like Messier 54 (the other extragalactic globular on Messier’s list), it is believed to not be native to the Milky Way galaxy at all, but instead to the putative Canis Major Dwarf Galaxy, which is currently experiencing a very close encounter with our galaxy. This is, however, a contentious subject as astronomers are still debating the nature of the Canis Major dwarf galaxy itself. Messier 79 may also be part of the Gaia Sausage.
M79 is a concentrated cluster, classified as Class V on the Shapley-Sawyer Concentration Class scale. This indicates a moderate concentration of stars. Unlike some other clusters, it is not a “core-collapsed” cluster, meaning its central stellar density does not follow the steep, power-law profile characteristic of clusters that have undergone this dynamical process.
The cluster is being disrupted by the galactic tide, trailing a long tidal tail.
Stellar and Chemical Composition
Like other ancient globular clusters, M79 is metal-poor, with its stars having a low abundance of elements heavier than helium and hydrogen. However, spectroscopic studies have confirmed that M79, despite its single stellar population appearance in a color-magnitude diagram, exhibits multiple stellar populations with distinct chemical signatures, particularly in elements like lithium and aluminum.
M79 is also home to a population of blue stragglers and other hot, luminous stars.