The gravity of the Sun, which is almost 28 times that of Earth, 'traps' hydrogen from its atmosphere and this hydrogen fuels the Sun’s fusion reaction. At temperatures of 15 million degree Celcius in the Sun's core, hydrogen gas becomes plasma, the fourth state of matter. In a plasma, the negatively charged electrons in atoms are completely separated from the positively charged atomic nuclei (or ions). The Sun's gravitational force confines the poistively-charged hydrogen nuclei and work with the high temperatures that cause the nuclei to move around furiously, collide at high speeds overcoming the natural electrostatic repulsion that exists between the positive charges and fuse to form the heavier helium.
- In the first stage two protons combine and one of them converts into a neutron to form a nucleus of the heavy isotope of hydrogen known as deuterium.
- Next, the deuterium nucleus combines with another proton to form the light helium isotope, known as helium-3.
- Finally, two helium-3 nuclei combine to form helium-4, releasing two protons.
Overall, four protons are converted into one helium nucleus. Energy is released because the helium nucleus has slightly less mass than the original four protons. The total amount of energy released for each conversion of four hydrogen nuclei into a helium nucleus is about 10 million times more than is produced by the chemical reaction when hydrogen combines with oxygen to form water