JoAnn Magiera, age 11, of Warwick, Rhode Island, for her question:

Why do stars appear different colors?

Things Up There are not always what they appear to be, But in this case they are. The stars really do come in different colors. In fact, astronomers classify them, on this basis. A powerful telescope reveals their colors very vividly, but we can see some of them with our own eyes. Stars, of course, are burning gases and each incandescent gas shows its own color. Those that retain most of their original hydrogen fuel shed white or blue white light. They are very very hot stars of classes     A, B and 0.

The brightest star in our summer sky is Antares, the glowing red giant at the heart of sprawling Scorpius, the Scorpion. Its blazing gases contain titanium oxide. Dazzling white Sirius has most of its hydrogen. The giant orange .red Arcturus has blazing metals. From far out in space, our sun shines as a golden class G star. It is hotter and has more incandescent metals than the red or orange red giants. It is cooler and has less hydrogen than the whites and blue whites.