solar constant amount of sun"s energy reaching earth is 1400 w/m2: every kg of the sun produces 0. 2 milliwatts of energy. this will continue through 10 billion years producing 3x10^13 j/kg: nuclear fusion. nucleus 1 + nucleus 2 nucleus 3 + energy. mass turned into energy e=mc2: like-charged nuclei get close enough to fuse eachother. only happens in high temperature over 10 million k. proton + proton deuteron + positron + neutrino. positron is like electron but positive charge. neutrino has no charge and very little mass. It is annihilated by collision with an electron resulting in a gamma ray. second step is formation of isotope of helium. final step: 2 helium -3 isotopes forms helium 4 and energy www. notesolution. com. gamma rays produced as byproducts of collisions at stage , ii, iii. electrons are freed during proton proton collision.