Annie Winkler, age 12, of Omaha, Nebraska, for her question:

What exactly is the diameter of Jupiter?

Measuring distant planets is tricky and astronomers keep using new techniques to refine their past figures. Based on the latest estimates, Jupiter appears to be larger than we used to think. Its mean diameter has been stretched almost 3,000 miles. The giant globe is flattened and its polar diameter is about 5,700 miles shorter than its bulging equatorial diameter. Its mean, or average, diameter now is estimated to be between 88,700 and 88,750 miles. This is slightly more than 11 times longer than the average diameter of the earth.

If giant Jupiter were hollow, it could swallow more than 1,300 earth sized planets. Of course it is not hollow, but it is made of surprisingly light materials. In spite of its enormous size, it weighs only about 318 times more than our little earth. Its total density is estimated to be 1.33 times the weight of an equal volume of water, while the earth's total density is 5.4. Jupiter is the largest of the planets by far, but for its size our small world is the heaviest of the planets.