Credit: Aldo Zanetti
Astronomical and Imaging Data
| RA: | 17h 01m 12.80s |
| DEC: | -30° 06′ 49.4″ |
| MAG: | 6.5 |
| Diameter: | 15′ |
| Const: | Oph |
| OTA | Celestron 9.25 Edge HD |
| Focal Length | 2350 |
| Camera | ASI2600MC |
| Site | Central Italy |
| Sky Quality | Bortle 3 |
Useful Informations
NGC 6266, also known as Messier 62 (M62), is a large and densely populated globular cluster in the constellation Ophiuchus. It is a particularly interesting object for astronomers due to its proximity to the Milky Way’s galactic center, which has significantly influenced its structure and dynamics.
Physical Characteristics and Structure
M62 is one of the most massive and luminous globular clusters in our galaxy. Its estimated mass is over a million times that of the Sun. It’s located approximately 22,200 light-years from Earth, but it’s much closer to the center of the Milky Way, at a distance of only about 5,500 light-years. This close proximity to the galactic core subjects M62 to intense tidal forces, which have likely distorted its shape, giving it an irregular, asymmetric appearance. Its central concentration is noticeably displaced from its geometric center.
Despite its high density, M62 is not considered a core-collapsed cluster. Its stellar density profile can be well-described by a standard King model, suggesting it has not yet undergone a complete core collapse.
Stellar Population and Exotic Objects
M62 is rich in exotic stellar objects, a common feature of dense globular clusters where stellar encounters are frequent. It hosts a large number of variable stars, including over 200 known RR Lyrae variables, making it one of the richest in this type of star in the Milky Way.
The cluster shows at least two distinct populations of stars, which most likely represent two separate episodes of star formation. Of the main sequence stars in the cluster, 79%±1% are from the first generation and 21%±1% from the second. The second is enriched by elements released by the first. In particular, abundances of helium, carbon, magnesium, aluminium, and sodium differ between these two. Indications are this is an Oosterhoff type I, or “metal-rich” system.
The cluster is also a prolific source of X-rays, which are emitted by stellar-mass black holes, millisecond pulsars, and binary star systems. The high stellar density in M62’s core provides a favorable environment for the formation of these systems through stellar collisions and close encounters. Evidence suggests the presence of binary millisecond pulsars, where a rapidly spinning neutron star is in a close orbit with another star. One such pulsar even has an orbiting exoplanet.
Furthermore, M62 has been a subject of research for a potential intermediate-mass black hole (IMBH) in its core, although a definitive confirmation remains elusive. Such an object would have a profound impact on the cluster’s dynamics.