L = (4πR^{2})σT_{eff}^{4}

f(v, v + Δv) = (\frac{m}{2πkT} )e^{−mv^{2}/2kT} 4πv^{2}Δv

t_{age} ≡ \frac{P}{dP/dt}

H ≡ \frac{T}{dT/dr}