Credit: Armen Akopian
Astronomical and Imaging Data
| RA: | 18h 18m 37.60s |
| DEC: | -52° 12′ 56.8″ |
| MAG: | 8.27 |
| Diameter: | 6.8′ |
| Const: | Tel |
| OTA | ASA 1000RC |
| Focal Length | 6500mm |
| Camera | FLI PL16803 |
| Site | El Sauce, Chile |
| Sky Quality | Bortle 1 |
Useful Informations
NGC 6584 is a globular cluster located in the southern constellation of Telescopium. It is an ancient, gravitationally bound sphere of stars that resides in the outer halo of the Milky Way, far from the obscuring gas and dust of the galactic plane. This remote location makes it an important object for studying the early history of our galaxy.
Key Scientific Properties
- Age and Metallicity: NGC 6584 is an old cluster, with an estimated age of about 11.6 billion years. Its stars are metal-poor, with a metallicity ([Fe/H]) of approximately -1.53, meaning its abundance of elements heavier than hydrogen and helium is significantly lower than that of the Sun. This property is a strong indicator of its age, as it suggests the stars were formed from the primordial gas of the early universe before it was enriched by generations of supernovae.
- Distance and Location: The cluster is located approximately 45,000 light-years from Earth. Its position in the galactic halo is notable: it orbits at a distance of about 4 kiloparsecs (kpc) from the Galactic Center and 2.7 kpc from the galactic plane. This remote location places it well outside the main disc of the Milky Way.
- Variable Stars: NGC 6584 is particularly rich in variable stars, which are stars that change in brightness over time. It has been classified as an Oosterhoff type I cluster, a classification based on the period-luminosity relation of its RR Lyrae variable stars. The cluster contains a large number of these variables, with at least 69 identified, including 46 RRab variables, 15 RRc variables, and a number of eclipsing binaries and long-period variables. Studying these variable stars provides crucial information about the cluster’s distance and age.
- Stellar Populations: As is typical for globular clusters, NGC 6584 hosts multiple stellar populations. This is reflected in the subtle differences in the chemical abundances and evolutionary tracks of its stars. The presence of a double main sequence or other complex features in its color-magnitude diagram points to different generations of stars that have formed within the cluster over time.