Joshua Wolin, age 10, of Cleveland Heights, Ohio, for his question:

How long does a star live?

A star does not blaze by the same process as a fire of coals. Nevertheless it burns and as it burns it consumes fuel. It is a nuclear powerhouse that consumes hydrogen gas, transforming it into helium gas. And, like a coal fire, it may burn fast or slow. The faster it burns the bigger and hotter the blaze and also the more fuel it consumes. It starts out with a built in quota of its own hydrogen fuel and when this supply is consumed, the star becomes a lifeless ball of dark, dead ashes.

Compared with life on earth, the life span of every star is very long. Astronomers estimate that some of the fast burning stars may burn themselves to ashes in perhaps a million earth years. This is about the shortest life expectancy 'for a star. Stars like our sun, that burn more slowly, can expect to live 20 to 30 billion years or so. Other stars burn even more slowly. Some of them may expect to live 50 to 100 billion years. At last, however, every star now shining will burn up all its fuel and go on its way as a cold dark ball of dead ashes.