We can estimate the temperature at which two
protons in a proton gas would (averagely) have enough energy to
overcome the coulomb barrier:
(3/2)k T = K ≃  400 keV, which gives T ~ 3 × 109 K When fusion is achieved by raising the temperature of the system so
that particles have enough kinetic energy to overcome the coulomb
repulsive behaviour, it is called thermonuclear fusion Thermonuclear fusion is the source of energy output in the interior
of stars The interior of the sun has a temperature of 1