Holly Wilson, Age 13, Of Portola Valley, Calif.., for her question:

How do you tell a star from a planet?

If you make a habit of star gazing, you will. Learn where to look for the planets. They travel in the certain belt called the zodiac; in this belt, the moon also crosses the sky. The stars are scattered all over the sky  the visible planets stay within the zodiac.

A bright object within the zodiac may or may not be a planet. The test is whether or not it twinkles. The stars all sparkle with sharp needles of light. The planets do not twinkle. You will have to watch it for a minute or two. Then, if your bright ob3ect has not sent out a darting arrow of light, you can be fairly sure that it is a planet.