Marie Coffen, age 10 of St. John's, Newfoundland, Canada, for her question:

What are superstars?

In the realm of astronomy, stars come in assorted sizes. Some are hot little white dwarfs, no bigger than planets. Others are medium sized stars more or less like our sun. And there are several classes of giant stars. The smallest of the giants is big enough to swallow a few thousand sun sized stars. A larger type is called a super giant star. If one of these whoppers were to replace our sun, it would engulf the orbits of Mercury and Venus, the earth and Mars. Some super giants would extend even beyond Jupiter and Saturn.

We might say that any of these giants are superstars because of their immense sizes. But perhaps we should reserve that term for a very rare celestial event. This occurs when an ordinary star suddenly explodes, shooting its blazing gases far out across a wide region of space. Its sudden glory outshines every star in the sky, though this phase lasts but a few years. Astronomers call this starry superstar a nova. Sometimes the explosion scatters almost the entire star    and this razzle dazzle event is called a supernova.