During hydrogen fusion in the Sun's core, what happens to matter?

• A. Matter is not involved.
• B. Some matter is converted into energy.
• C. All matter is converted into energy.
• D. Matter remains unchanged.

Answer: (B)

When hydrogen fuses in the Sun’s core, mass is not just rearranged—some of it is actually turned into energy. In the proton-proton fusion process that builds helium, the total mass of the resulting helium nucleus and other particles is slightly less than the mass of the four protons that went into it. That missing mass becomes energy according to E = mc^2, releasing gamma rays, neutrinos, and other radiation. This energy ultimately powers the Sun’s heat and light. Most of the mass remains in the new particles, but a small fraction is converted to energy, which is why the Sun shines.