Credit: Aldo Zanetti
Astronomical and Imaging Data
| RA: | 23h 08m 26.63s |
| DEC: | -15° 36′ 41.4″ |
| MAG: | 11.29 |
| Diameter: | 4.2′ |
| Const: | Aqr |
| OTA | Celestron 9.25 Edge HD |
| Focal Length | 2350 |
| Camera | ASI1600MM |
| Site | Po Plain, Italy |
| Sky Quality | Bortle 7 |
Useful Informations
NGC 7492 is a very distant and diffuse globular cluster located in the constellation Aquarius. It is a key object for studying the outer regions of the Milky Way’s galactic halo and the history of galaxy mergers.
Key Properties and Location
NGC 7492 is situated at an immense distance from Earth, approximately 80,000 light-years away. Its location in the outer galactic halo, far from the Milky Way’s main disk, makes it a valuable tracer of the galaxy’s gravitational potential at its fringes. It is classified as a Class XII globular cluster, which means it is extremely sparse and has a very low central concentration of stars. This low density and its significant distance make it a challenging object for observation.
Recent research has revealed that NGC 7492 is not a native member of the Milky Way’s globular cluster system but is instead part of the Sagittarius Stream, a long tidal tail of stars torn from the Sagittarius Dwarf Spheroidal Galaxy. The discovery of a tidal tail around NGC 7492, stretching over 3.5 degrees on the sky, further supports the idea that this cluster was dynamically stripped from a captured dwarf galaxy.
Stellar and Chemical Composition
NGC 7492 is an ancient stellar system, with an estimated age of about 12 billion years. Its stars are metal-poor, with a very low abundance of elements heavier than hydrogen and helium. This low metallicity is consistent with its old age and its origins in a dwarf galaxy that formed in the early universe.
The cluster’s color-magnitude diagram shows a well-defined but sparsely populated red giant branch and a horizontal branch. While it has a population of variable stars and blue stragglers, the overall low density and faintness of the cluster make detailed studies of its individual stars more difficult than for denser, brighter clusters.
Its flattened shape, rather than the typical spherical shape of a globular cluster, is also likely the result of strong tidal interactions with the Milky Way.