Animation of the internal structure of the Sun. The outermost layer is the photosphere, which is the layer from which the light is emitted, and where sunspots are found. The photosphere gets more and more opaque until it reaches the convective zone orange. This layer consists of hot plasma charged particles of gas that rise from within the Sun by convection, cool at the photosphere and fall back into the Sun. This continuous rising and falling causes the granulation seen on the photosphere. Within the convective zone is the radiative zone yellow, which consists of plasma that is hot and dense enough for convection to be impossible, and heat is transferred by radiation, that is, the emission of photons. Within the radiative zone is the core white. This is the site of the nuclear fusion reactions that power the Sun. At temperatures of more than 15 million Kelvin, hydrogen atoms fuse together to form helium atoms, releasing energy in the process. It is this energy that travels outwards through the overlying layers.