<P> In a radiative zone, the temperature gradient--the change in temperature (T) as a function of radius (r)--is given by: </P> <Dl> <Dd> d T (r) d r = − 3 κ (r) ρ (r) L (r) (4 π r 2) (16 σ) T 3 (r) (\ displaystyle (\ frac ((\ text (d)) T (r)) ((\ text (d)) r)) \ =\ - (\ frac (3 \ kappa (r) \ rho (r) L (r)) ((4 \ pi r ^ (2)) (16 \ sigma) T ^ (3) (r)))) </Dd> </Dl> <Dd> d T (r) d r = − 3 κ (r) ρ (r) L (r) (4 π r 2) (16 σ) T 3 (r) (\ displaystyle (\ frac ((\ text (d)) T (r)) ((\ text (d)) r)) \ =\ - (\ frac (3 \ kappa (r) \ rho (r) L (r)) ((4 \ pi r ^ (2)) (16 \ sigma) T ^ (3) (r)))) </Dd> <P> where κ (r) is the opacity, ρ (r) is the matter density, L (r) is the luminosity, and σ is the Stefan--Boltzmann constant . Hence the opacity (κ) and radiation flux (L) within a given layer of a star are important factors in determining how effective radiative diffusion is at transporting energy . A high opacity or high luminosity can cause a high temperature gradient, which results from a slow flow of energy . Those layers where convection is more effective than radiative diffusion at transporting energy, thereby creating a lower temperature gradient, will become convection zones . </P>

3 facts about the sun's radiation zone