The Sun's energy is produced by the fusion of hydrogen into helium. Which process is this?

• A. Nuclear Fusion
• B. Solar Wind
• C. Hydrogen Gas
• D. Comets

Answer: (A)

Nuclear fusion is the process by which light atomic nuclei join to form a heavier nucleus, releasing energy in the process. In the Sun’s core, extremely high temperatures and pressures allow hydrogen nuclei to collide and fuse into helium, powering the Sun’s light and heat through reactions like the proton-proton chain. The energy released during these fusion reactions travels outward to radiate as sunlight and warmth for the solar system. This stands in contrast to the other terms: solar wind is a stream of charged particles escaping the Sun, not the energy source; hydrogen gas is just a state of matter; comets are icy bodies that orbit the Sun. So the energy production described is nuclear fusion.