The correct answer is:
from the energy need to fuse the atoms together
Fusion is the process which powers the sun and the stars. It is energy that makes all life on earth possible. It is called 'fusion' because the energy is produced by fusing together light atoms, such as hydrogen, at the extremely high pressures and temperatures which exist at the centre of the sun (15 million ºC). At the high temperatures experienced in the sun any gas becomes plasma, the fourth state of matter (solid, liquid and gas being the other three).
The fusion reaction that is easiest to accomplish is the reaction between two hydrogen isotopes: deuterium, extracted from water and tritium, produced during the fusion reaction through contact with lithium. When deuterium and tritium nuclei fuse, they form a helium nucleus, a neutron and a lot of energy.
