NGC 6397

Located in the direction of Ara it is one of the closest globular clusters to us (about 7,800 ly from Earth), 68 ly in diameter and has a mass of about 1.1x10⁵ solar masses. It contains about 400,000 stars and is one of at least twenty such Milky Way objects that have experienced core collapse to a very dense concentration of compact objects. The nature of these objects - white dwarfs, neutron stars, black holes - was uncertain until recently, when observations of stellar motions around gravitating masses in the core were best explained by models that assumed the masses to be solely white dwarfs, though numbering in the hundreds.  As globular clusters go, it is relatively metal-poor. 

Classified as IX (loose towards the centre) on the Shapley-Sawyer globular cluster concentration scale (1927).