What is the nuclear fuel in the sun? Describe the process by which energy is released in the sun. Write the equation of the nuclear reaction involved.

Hydrogen gas is the nuclear fuel in the sun as the sun derives its energy from the fusion of hydrogen nuclei.

Nuclear fusion is the process by which energy is released in the sun. In this reaction, four hydrogen atom nuclei fuse to form the bigger nucleus of the helium atom and release a tremendous amount of energy.  Here, the mass gets lost during these fusion reactions and energy is being produced in the form of heat and light.

Reaction:

$4_{1}^{1} \mathrm{H}$  $\displaystyle \xrightarrow[inside\ the\ sun]{nuclear\ fusion}$  $_{2}^{4} \mathrm{He}+2_{1}^{0} \mathrm{e}+Tremendous\ amount\ of\ energy$