L_{star} = 4πR_{s}^{2}σT_{s}^{4}

L_{planet} = 4πR_{p}^{2}σT_{p}^{4}

ratio of fluxes = \frac{L_{planet}}{L_{star}} = (\frac{R_{p}^{2}}{R_{s}^{2}} )(\frac{T_{p}^{4}}{T_{s}^{4}} )