Credit: Aldo Zanetti
Astronomical and Imaging Data
| RA: | 12h 39m 27.98s |
| DEC: | -26° 44′ 38.6″ |
| MAG: | 7.84 |
| Diameter: | 11′ |
| Const: | Hya |
| OTA | Celestron 9.25 Edge HD |
| Focal Length | 2350 |
| Camera | ASI2600MC |
| Site | Central Italy |
| Sky Quality | Bortle 3 |
Useful Informations
NGC 4590, also known as Messier 68 (M68), is a globular cluster located in the constellation Hydra. It is a very old and metal-poor stellar system, notable for its distinct stellar population and its unusual location in the galactic halo.
Physical Properties and Location
M68 is situated about 33,000 light-years from Earth and is estimated to contain at least 100,000 stars. It’s a particularly intriguing cluster due to its position in the sky, as it is located on the side of the sky opposite to the center of the Milky Way. This, along with its high velocity and metal-poor nature, has led some astronomers to suggest that M68 may be a “leftover” from a dwarf galaxy that was captured and absorbed by the Milky Way in the distant past.
The cluster has a relatively low concentration of stars, and is classified as a Class X globular cluster on the Shapley-Sawyer scale. This means its stars are not as densely packed in the core as in other, more concentrated clusters.
It is orbiting our galaxy’s galactic bulge with a great eccentricity of 0.5. This takes it to 100,000 light years from the center.
Stellar and Chemical Composition
Like other ancient globular clusters, M68 is extremely metal-poor, with a metallicity of only about 1% of the Sun’s. This low abundance of elements heavier than helium and hydrogen is a strong indicator of its great age, which is estimated to be over 11 billion years.
Despite this overall low metallicity, M68 exhibits a phenomenon known as multiple stellar populations, where stars within the cluster show variations in the abundances of light elements like sodium and oxygen. This suggests that the cluster has had more than one star formation event or that its stars formed from chemically different gas environments.
The cluster also contains a significant number of variable stars and most of them are of type RR Lyrae, or periodic variables. Six of the variables are of the SX Phoenicis variety, which display short pulsating behavior.