Stellar core

The core of a sun is where the nuclear fusion processes occur. The heat and pressure in this area is so high that hydrogen is fused to become helium. Four hydrogen atoms become two protons, two neutrons, one neutrino and one gamma ray (the two protons and the two neutrons make the helium atom) in a process called "the Proton-Proton chain".

The gamma ray contains an extreme amount of energy, but much of this energy will be lost through collisions with other atoms as the ray travels from the center outwards to reach space.

In a typical main sequence sun, the core holds about 50% of the sun's total mass. The temperature of the core is about 15 million K and the density is about 150 g/cm^3 (approximately 10 times the density of gold or lead). The hydrogen burning core extends to about 25% (approx. 175 000 km) of the solar radius. The temperature at the edge of the core is halved and the density drops to 20g/cm^3.