what fuels the sun to keep shining ( Archived) (13)

Nuclear fusion is what happens in the Sun – it’s the combining of light elements into heavier elements to produce energy.

The Sun produces a large amount of energy by combining very light elements such as hydrogen to heavier elements such as helium and then lithium, oxygen, carbon, right up to iron. They combine because, once you get the nuclei sufficiently close together, there is a very strong attractive force called the nuclear force which holds them together.

The combination of the two masses is slightly less than the masses individually. So E=mc2, a very small change in mass will give you a very large change in energy because c is of course the velocity of light, which is 3 x 108 metres per second.

So normal nuclear power reactors are what’s called fission reactors – they split very heavy elements such as uranium into small bits and get energy. The Sun, however, works by combining very light nuclei such as hydrogen to make helium, and you also gain energy, but to get them that close is very, very difficult, and it needs extremely high temperatures, and that’s what you’ve got in the Sun.