<P> The rate of nuclear fusion depends strongly on density . Therefore, the fusion rate in the core is in a self - correcting equilibrium: a slightly higher rate of fusion would cause the core to heat up more and expand slightly against the weight of the outer layers . This would reduce the fusion rate and correct the perturbation; and a slightly lower rate would cause the core to cool and shrink slightly, increasing the fusion rate and again reverting it to its present level . </P> <P> However the Sun gradually becomes hotter during its time on the main sequence, because the helium atoms in the core are denser than the hydrogen atoms they were fused from . This increases the gravitational pressure on the core which is resisted by a gradual increase in the rate at which fusion occurs . This process speeds up over time as the core gradually becomes denser . It is estimated that the sun has become 30% brighter in the last four and a half billion years and will continue to increase in brightness by 1% every 100 million years . </P> <P> The high - energy photons (gamma rays) released in fusion reactions take indirect paths to the Sun's surface . According to current models, random scattering from free electrons in the solar radiative zone (the zone within 75% of the solar radius, where heat transfer is by radiation) sets the photon diffusion time scale (or "photon travel time") from the core to the outer edge of the radiative zone at about 170,000 years . From there they cross into the convective zone (the remaining 25% of distance from the Sun's center), where the dominant transfer process changes to convection, and the speed at which heat moves outward becomes considerably faster . </P> <P> In the process of heat transfer from core to photosphere, each gamma ray in the Sun's core is converted during scattering into several million visible light photons before escaping into space . Neutrinos are also released by the fusion reactions in the core, but unlike photons they very rarely interact with matter, so almost all are able to escape the Sun immediately . For many years measurements of the number of neutrinos produced in the Sun were much lower than theories predicted, a problem which was recently resolved through a better understanding of neutrino oscillation . </P>

Where would the most high energy photons be found in the sun
find me the text answering this question