All of the electromagnetic energy radiated from the sun (and from other stars) is the product of nuclear fusion in its core.
Heat waves are the** radiation** released from the Sun, the energy and the light is what is visible of this emission of energy.
Heat and light waves from the sun are produced by nuclear fusion occurring in its core, where hydrogen fuses into helium and releases energy. This energy travels through the sun's layers and is emitted as electromagnetic waves, including visible light and heat. Ultimately, this energy reaches Earth as sunlight.
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