Blast Off to Success with the 2026 Abeka Science Earth and Space Practice Test – Your Time to Shine!

Stars get their energy from nuclear fusion in the core, where light hydrogen nuclei combine to form heavier helium. This fusion releases energy because some of the mass of the resulting helium is converted into energy, per E=mc^2. The core temperatures reach millions of kelvin and the enormous pressures push protons close enough for the strong nuclear force to bind them, allowing hydrogen to fuse through processes like the proton-proton chain (and the CNO cycle in heavier stars).

Nuclear fission, which splits heavy nuclei, isn’t how stars produce energy. Nuclear decay involves the spontaneous breakdown of unstable nuclei and is too slow to power a star. Chemical reactions release energy from electronic bonds and are far less energetic than nuclear processes, so they can’t sustain stellar luminosity. Therefore, hydrogen fusing into helium via nuclear fusion is the correct mechanism powering stars.