Globular Cluster Core Collapse

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 simulator renders a 3D cluster of 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, 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.