Question: Do you know why stars shine?

Adam Tuff answered on 14 Mar 2011:

We know now that stars shine because of the nuclear reactions that take place inside them. Stars are huge balls of gas, and deep inside the stars the presure of all the material above it on the surface is so heavy, it creates a place where it is hot enough for “fusion” reactions to occur. These are different to the reactions we use in our power stations (which break atoms to get energy) – instead these reactions cause atoms to join together to release energy. Only a tiny amount of the hydrogen needs to be fused to make a lot of energy – 1kg of fused hydrogen produces the same amount of energy as 20,000 tons of burnt coal – isn’t that incredible?

The sun produces a lot of light, but it only uses a tiny tiny proportion of it’s mass to make heat, which is why stars last for billions of years.