Carl Stack, age 16, of Thousand Oaks, Calif., for his question:

WHAT IS ALPHA CENTAURI?

Alpha Centauri is a multiple star that can be found in the constellation Centaurus. It is the third brightest star in the heavens, exluding the sun. Also, it is the nearest star to Earth, except for the sun.

Alpha Centauri is actually a multiple star. Although it appears to be a single star, it is actually made up of three individual stars. The closest star in the group is 4.3 light years away. Alpha Centauri can only be seen in the Southern Hemisphere.

The constellation Centaurus received its name from the centaurs of Greek mythology. Centaurs were creatures that were half man and half horse. The stars that form the hind legs in the constellation Centaurus also belong to the constellation Crux, the Southern Cross.