Brad Heck, age 9, of Allentown, Penn., for his question:

How long will the sun last?

Maybe you have heard that someday our starry sun will turn into a lump of cold dead ashes. True, this may happen. But certainly we do not have to worry about it. There is no need at all to stay awake at night, dreading the time when the sun will stop shining. If it happens, the time will be far far in the future. The people who live 100 years from now need not worry. The sun will shine even on the folks who will live 1,000 or 10 million years in the future.

Our sun is a fairly ordinary star. Scientists tell us that it has a life story that has lasted many billions of years. They suspect that it was created from an enormous cloud of dusty gases. It has been blazing away for 5 billion years  and in all that time it has used up hardly half of its fuel. Scientists are sure that it will keep going in the same old way for at least another 5 billion years. Most likely it will last much longer, maybe 10 or even 12 billion years more.