Globular Cluster Core Collapse (2D)

Globular clusters are among the oldest, densest stellar systems in the galaxy, and their cores evolve under a genuinely strange rule: because a self-gravitating system has negative heat capacity, a core that radiates away kinetic energy through two-body star-star encounters must shrink and heat further to stay in equilibrium — a runaway called the gravothermal catastrophe. This top-down 2D simulator renders a cluster of hundreds to thousands of stars in two mass classes, drives the core radius through a simplified similarity-solution collapse, and segregates heavier stars inward exactly as equipartition predicts. Push the relaxation rate up to watch the collapse accelerate, drag and scroll to explore the cluster, and toggle binary-star heating to see the difference between an unphysical collapse to a point and the real, observed outcome: three-body binaries injecting energy back into the core and forcing it into repeating gravothermal oscillations, tracked live on the strip chart below the cluster view.