ABSTRACT
Nuclear physics gives a self-consistent picture of the energy source for the Sun and its subsequent lifetime, as the age of the solar system derived from meteoritic abundances of lead and uranium isotopes is about 4.5 billion years. As stars produce their energy by nuclear fusion reactions, the positive charges of two reacting nuclei will try to oppose the nuclei getting too close together by forming a Coulomb Barrier between them. According to the theory of stellar structure and evolution stars are selfgravitating balls of hydrogen gas that act as thermonuclear furnaces to convert the primary product of the big bang into the heavier elements of the periodic table. For a massive star having the temperature and density high enough, after the exhaust of most of the hydrogen in the star due to transmutation into helium, the stellar core can be hot enough for helium burning to take place.
