How is energy released in stars and how does this effect the composition of elements in the universe?
Answer Hello, Energy is released in stars by the process of nuclear fusion which can take different forms, with different reactions producing different amounts of energy depending on the reactants. In the Sun, for example, “hydrogen fusion” (into helium) leads to the basic set of three reactions for the proton-proton cycle, viz. H1 + H1 + e -> D2 + v + energy D2 + H1 -> He 3 + (gamma) + energy He3 + He 3 -> He 4 + H1 + H1 + energy In the first, H1 denotes the proton (hydrogen nucleus), e is an electron, D2 is deuterium – an isotope of hydrogen- and v is the neutrino, and energy given off. This leads to the next reaction, with deuterium fusing with a proton to yield the isotope helium 3, a gamma ray and more energy given off. Finally, this leads to the end stage reaction, with the helium 3 combining with another helium 3 nucleus to give helium 4, two more protons (to start the cycle anew) and energy given off. Eventually, as these reactions progress, hydrogen is used up in the core, and
