the energy of the stars was produced by nuclear fusion, the temperatures required in the stars being lower than those needed in the laboratory because of the enormous pressures in the stellar interiors.
Reaction that occurs in the Sun are :
1. p-p chain reaction
2. The main source of energy in hotter stars is the carbon cycle (also called the CNO cycle for carbon, nitrogen, and oxygen), in which hydrogen is transformed into helium, with carbon serving as a catalyst.