Animation of the Sun, showing it opening to reveal its internal structure, which is labelled. The nuclear reactions that power the Sun take place in the hot, dense central core, which extends to about a quarter of the Sun's radius. Here hydrogen fuses into helium, releasing energy. Above this is the radiative zone, where the energy is transferred between particles by energetic photons. This situation persists to about 70% of the Sun's radius, above which the overlying layers are cool and rarefied enough to permit convection, which occurs in the outer convective layer (orange). Here, hotter, less dense pockets of plasma rise to the surface, cool and sink (shown by arrows), producing the granulation cells visible on the Sun's surface. For this clip with English text labels, see K009/4745. For a version without labels, see K009/4744.