Gail Garofalo, age 12, of Warmister, Pennsylvania, for her question:

What really makes a star shine?

We could say that a star is on fire, pouring forth heat and light. But that answer is too simple and besides, it is not strictly true. When we talk about fire, we mean the blazing combustion that goes on in a burning campfire. A star is not this sort of fire at all. The chemical combustion of a campfire requires oxygen fuel. The blazing activity of a star does not. It is powered by thermonuclear activity, the same type of atomic activity in the hydrogen bomb. Nuclear scientists are sure how the seething process works. And they are quite sure that some sort of nuclear activity is responsible for the light of the shining stars.

Nuclear activity changes the nuclei (or cores) of tiny atoms. Most likely a star burns by nuclear fision, a process that fuses smaller atoms to make larger ones. A nucleus is made of several atomic particles. When two nuclei fuse together, matter is converted into energy    into the seething nuclear energy that pours forth from a blazing star.