An Interactive Introduction to How Stars Make Energy
Fusion energy is produced when two light atomic nuclei combine to form a heavier nucleus. This process powers the Sun and all stars.
This relationship is described by Einstein’s famous equation: E = mc².
Atomic nuclei experience two competing forces that determine whether fusion can occur.
Like charges repel. Protons push each other apart.
At very short distances, it pulls nuclei together.
Fusion happens only when nuclei get close enough for the strong force to overcome repulsion.
When two hydrogen nuclei fuse, the resulting nucleus has slightly less mass than before.
The missing mass becomes energy — released as heat and radiation.
To achieve fusion on Earth, fuel must be heated to over 100 million degrees Celsius.
Matter becomes plasma, an ionized gas of charged particles.
Magnetic fields are used to contain plasma so it does not touch the reactor walls.