Dark matter

Dark matter, most of the invisible material existing in galaxies and clusters of galaxies. Dark matter does not produce, cast, or absorb light, and is 10 times more prevalent than visible matter. Astronomers have determined the amount of dark matter in a galaxy by finding the orbital speed of gas clouds and stars. They conclude that amounts of dark matter were always greater than amounts of visible matter in both galaxies and clusters of galaxies.

See also: Galaxy.