Credit: Aldo Zanetti
Astronomical and Imaging Data
| RA: | 20h 53m 27.70s |
| DEC: | -12° 32′ 14.3″ |
| MAG: | 9.27 |
| Diameter: | 6.6′ |
| Const: | Aqr |
| OTA | Celestron 9.25 Edge HD |
| Focal Length | 2350 |
| Camera | ASI1600MM |
| Site | Po Plain, Italy |
| Sky Quality | Bortle 7 |
Useful Informations
NGC 6981, also known as Messier 72 (M72), is a globular cluster located in the constellation Aquarius. It’s one of the more distant globular clusters associated with the Milky Way and is a subject of interest for its stellar properties and its location in the galactic halo.
Key Physical Properties
M72 is located approximately 54,600 light-years from Earth and about 60,800 light-years from the Galactic Center. It is classified as a Class IX globular cluster on the Shapley-Sawyer Concentration Class scale, meaning it has a relatively low concentration of stars compared to more dense clusters. Its estimated mass is around 168,000 solar masses, and its age is about 9.5 billion years, making it younger than many other globular clusters.
Stellar and Chemical Composition
Like other globular clusters, M72 is metal-poor, with a metallicity of about 1.3% of the Sun’s. This low abundance of heavier elements is a hallmark of ancient stellar populations. However, studies of its stellar populations reveal a complex picture. The cluster has a notable population of variable stars, including around 43 confirmed variables, most of which are of the RR Lyrae type. These pulsating stars are crucial for determining the cluster’s distance and for understanding stellar evolution.
Recent research has also shown that the cluster’s stars are not all uniform in chemical composition, suggesting that M72 may have experienced a more complex formation history than a simple single star-forming event.