The type of nuclear reaction that occurs in the sun is called nuclear fusion. This process involves the merging of lightweight atomic nuclei, primarily hydrogen, to form heavier elements, such as helium, releasing tremendous amounts of energy in the form of radiation. Fusion occurs in the sun's core under extreme temperatures and pressures, where gravitational forces create conditions favorable for these reactions. The energy produced through fusion not only powers the sun but also influences the radiation received on Earth, providing warmth and energy essential for sustaining life and supporting various ecosystems.