Look up on a clear night, far away from city lights, and you will see thousands of stars. If you look closer, you might notice that the stars shine with an amazing variety of colors. Some glow dull red, some blue, some yellow like the sun, and some bright white. The picture to the right shows three stars as seen by the SDSS.

But what exactly is color? Why do stars have different colors? And what can you learn by studying the colors of stars, galaxies, and other objects?

Click Next to find out.