Please, correct my essay.

The sun has been burning for over four and half billion years. It is approximately 8 light-minutes away from our planet and is the nearest star. The lecturer explains three layers of the sun. The first one is the core. Here gravity pulls all elements together causing great pressure that result in nuclear fission. The next layer is the radiative zone. In this zone photons travel outwards and are absorbed by gas molecules. The last layer is the convective zone. Within this space there is a constant exchange of hot gases and cool gases. The transfer of photons is faster than in the other two zone.