Credit: Aldo Zanetti
Astronomical and Imaging Data
| RA: | 17h 23m 58.59s |
| DEC: | -26° 21′ 12.3″ |
| MAG: | 9.14 |
| 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 6355 is a globular cluster located in the constellation Ophiuchus. This ancient and compact cluster is a fascinating subject of study because of its extreme age, metal-poor nature, and location within the crowded inner region of the Milky Way galaxy.
Physical and Chemical Properties
- Distance and Location: NGC 6355 is located approximately 28,000 light-years from Earth. It’s situated in the Galactic bulge, the dense, central region of our galaxy. Its position makes it challenging to study, as it’s heavily obscured by interstellar dust and lies within a crowded star field.
- Age and Metallicity: The cluster is estimated to be incredibly old, with an age of about 13.2 billion years. This places it among the oldest known objects in the Milky Way. Its stars are metal-poor ([Fe/H]≈−1.39 dex), which is consistent with its formation from the pristine gas of the early universe.
- Structure: NGC 6355 is a core-collapsed cluster, meaning its core has undergone a gravitational contraction, leading to an extremely high density of stars at its center. This state is a common feature of many massive globular clusters and is a result of their long-term dynamical evolution.
Scientific Significance
NGC 6355’s unique properties make it a valuable target for research.
- Tidal Tails: Recent observations have confirmed the presence of tidal tails—streams of stars gravitationally stripped from the cluster as it orbits the galactic center. The detection of these tidal tails, which point toward the Milky Way’s center, is particularly significant because it’s rare to find such structures in clusters so deeply embedded in the galactic bulge. This provides direct evidence of the cluster’s interaction with the powerful gravitational forces of the Milky Way’s core.
- Stellar Population: Like other globular clusters, NGC 6355 contains a stellar population that is coeval (formed at the same time), but recent studies suggest chemical inhomogeneities among its stars. The presence of these chemically distinct stellar populations offers clues about the complex process of star formation and enrichment in these ancient systems.