The core of the Sun maintains a temperature near 1.5×107K and a density of roughly 1.6×105kgm−3. In this environment, protons undergo a series of reactions that ultimately yield helium nuclei and release large amounts of energy.
(1) Describe the role of electrostatic repulsion in determining the minimum conditions necessary for two protons to come within a range where the strong nuclear force becomes attractive.
(2) Explain why extremely high temperature and density together increase the probability that proton–proton fusion will occur inside the Sun, even though individual protons still possess kinetic energies much smaller than the peak of the Coulomb barrier.
(3) Discuss how quantum mechanical tunneling allows fusion to proceed at the observed solar core temperature, and describe qualitatively how tunneling probability depends on the width and height of the effective potential barrier.
(4) Identify whether the overall proton–proton chain occurring in the Sun is best described as spontaneous or induced, and justify your answer based on the environmental conditions present in the core.