Credit: Aldo Zanetti
Astronomical and Imaging Data
| RA: | 17h 44m 54.65s |
| DEC: | +03° 10′ 12.5″ |
| MAG: | 11.01 |
| Diameter: | 4.2′ |
| Const: | Oph |
| OTA | RC 12″ |
| Focal Length | 2432 |
| Camera | PlayerOne Poseidon M |
| Site | Central Italy |
| Sky Quality | Bortle 4 |
Useful Informations
NGC 6426 is a sparsely populated and very old globular cluster located in the constellation Ophiuchus. It’s considered one of the most metal-poor and ancient globular clusters in the Milky Way’s halo, providing important clues about the chemical evolution of the early galaxy.
Physical and Chemical Characteristics
- Age and Metallicity: NGC 6426 is an exceptionally old stellar system, with an estimated age of around 13 billion years. Its stars are extremely metal-poor, with a low abundance of elements heavier than hydrogen and helium. The low metallicity and ancient age suggest it formed from primordial gas clouds very early in the universe’s history.
- Structure: Unlike the dense, compact cores of many globular clusters, NGC 6426 has a low concentration of stars. It is classified as a Shapley-Sawyer Concentration Class IX, which means its stars are only slightly condensed toward the center. This loose structure makes it a difficult object to observe, but it also indicates a dynamically young cluster that has not undergone significant gravitational collapse.
- Location: It’s situated in the outer galactic halo, approximately 67,000 light-years from the Sun and around 47,000 light-years from the galactic core. Its distant location and low density make it a key object for studying the kinematics of the outer galactic halo and the properties of the Milky Way’s dark matter distribution.
Scientific Significance
NGC 6426 is a valuable “laboratory” for understanding the chemical evolution of the first stellar generations. Studies of the cluster’s chemical composition, particularly the abundance of certain elements, suggest that the gas from which it formed may have been enriched by the remnants of ancient, massive stars, possibly from hypernovae (extremely powerful supernovae). Additionally, the presence of a carbon star near its core is a rare discovery in a metal-poor cluster like this, offering insights into the later stages of stellar evolution under these conditions. Its population of RR Lyrae variable stars also helps astronomers classify the cluster and determine its age and distance.