The Role of "Black Hole Burning" in the Evolution of Dense Star Clusters

Understand

As self-gravitating systems, dense star clusters exhibit a natural diffusion of energy from their innermost to outermost regions, which leads to a slow and steady contraction of the core until it ultimately collapses under gravity.

• However, in spite of the natural tendency toward so-called "core collapse," the globular clusters (GCs) in the Milky Way exhibit a well-observed bimodal distribution in core radii separating the core-collapsed and non-core-collapsed clusters.
• This suggests an internal energy source is at work, delaying the onset of core collapse in many clusters.
• Primordial binary stars have been thought for a long time to provide this energy source, but recent analyses have cast doubt upon the corresponding "binary-burning" mechanism as a viable explanation.