Power-law planetary cooling
= Power-law planetary cooling
{title2=$L_{\rm int}\propto t^{-\alpha}$}
If otherwise comparable isolated <planets> of one <mass> follow $L_{\rm int}=Ct^{-\alpha}$, their intrinsic <luminosity> ratio is $L_{\rm int}(t_1)/L_{\rm int}(t_2)=(t_2/t_1)^\alpha$. The normalization depends on composition and initial <entropy>. Strong stellar irradiation, deep heating, or accretion can invalidate extrapolating the same cooling law.