What process powers the Sun?

• A. Nuclear fission
• B. Chemical combustion
• C. Nuclear fusion
• D. Gravitational contraction

Answer: (C)

Energy production in the Sun comes from nuclear fusion in its core, where extreme temperatures and pressures force hydrogen nuclei to fuse into helium. When these fusion reactions occur, some of the mass is converted into energy (via E=mc^2), releasing photons and particles that heat the solar interior. This energy then slowly travels outward and emerges as sunlight. Gravitational contraction was important during the Sun’s formation, but it doesn’t supply the Sun’s energy on an ongoing basis. Chemical combustion can’t power the Sun because it requires chemical bonds and external reactants at relatively low energies, which is impossible under stellar core conditions. Nuclear fission isn’t the main process because the Sun’s composition and environment favor fusion of light nuclei, not the splitting of heavy ones.