Stars give out heat and light due to continuous fusion and fission reaction of hydrogen and helium in it. These reactions release a tremendous amount of energy in the form of heat and light. helium atoms. During this process, huge amount of energy is released in the form of heat and light.
The intense pressure and temperature at the core of a starallow nuclear fusion reactions to take place. This is where atoms of hydrogen are fused into atoms of helium (through several stages). This reaction releases an enormous amount of energy in the form of gamma rays
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