Energy generation in the Sun arises because hydrogen nuclei fuse to form helium nuclei. Write down the reactions involved in the proton-proton chain. State which reaction in the chain controls the rate at which the full set of reactions proceeds and explain why this is the case. Given that the solar luminosity is L = 3.8 × 1026 W, the combined mass of four protons is 6.690 × 10−27 kg and the mass of one helium nucleus is 6.643 × 10−27 kg, estimate the number of helium nuclei that have been generated inside the Sun over its 4.6 × 109 year life time.

Energy generation in the Sun arises because hydrogen nuclei fuse to form helium nuclei. Write down the reactions involved in the proton-proton chain. State which reaction in the chain controls the rate at which the full set of reactions proceeds and explain why this is the case. Given that the solar luminosity is L = 3.8 × 1026 W, the combined mass of four protons is 6.690 × 10−27 kg and the mass of one helium nucleus is 6.643 × 10−27 kg, estimate the number of helium nuclei that have been generated inside the Sun over its 4.6 × 109 year life time.