Teresa Lo, age 12, of Burnaby, British Columbia, Canada, for her question:

WHAT IS A BLACK HOLE IN SPACE?

Some astronomers believe that what is called a black hole in space may actually be the area occupied by a large star which collapsed and fell inward from its own weight. They believe that perhaps the star compressed as it collapsed and its density increased tremendously. The force continues so strong that nearby objects, such as comets and planets, continue to orbit. The force is also so great that even the star's light cannot escape.

The black hole theories have not been proven.

Many astronomers, however, believe that black holes make up as much as a third of the material in the earth's galaxy, the Milky Way.