Perhaps this should be on the homework forum but I'm not sure, so I put it here. How do you calculate the cooling time scale of the surface of a white dwarf and the surface of the core of a white dwarf? I have an equation for the cooling scale of a white dwarf in general but I'm not sure how exactly to correlate this to the cooling scale of the surface and the cooling scale of the surface of the core. Even just a suggestion on how to relate those two would be great, but something more in detail is always appreciated. Thanks for your time.