Kelvin-Helmholtz cooling time (${\tau }_{\mathrm{KH}}\sim G{M}^2/(R{L}_{\mathrm{int}})$)

The Kelvin-Helmholtz cooling time estimates how long a self-gravitating body can radiate a reservoir of energy of order its gravitational binding energy. It uses intrinsic luminosity $L_{\mathrm{int}}$, excluding reradiated stellar light. At fixed radius and structure, this reservoir scales as $M^2$; the approximation changes when degeneracy or other internal physics changes the accessible energy.