Butch Callegari, age 11, of Houston, Texas for his question:

How old is the sun?

Astrophysicists must solve many problems before they can compute the exact age of the sun. However, they have enough indirect evidence to make an educated guess. Most agree that our personal star is most likely about five billion years old. Further evidence may add or subtract a few hundred million years. This estimate is based on what they know or suspect about a wide variety of astronomical fields.

One is the origin of the Solar System, when and how it was formed and at what stage the mighty sun ignited its nuclear furnace. Ancient crustal rocks can be dated to reveal that the earth and moon may be four billion years old. Obviously the sun is this old and most likely older. Information on how stars burn their hydrogen fuel provides other clues. The mixture of the sun's gases suggests that about half its original fuel is consumed. Comparing this with its present rate of burning, scientists have estimated that it has been burning for about five billion years.