Among the constellations the Milky Way passes through are Carina, Crux (the Southern Cross), Sagittarius (where it is brightest), Scorpius, Aquila, Cygnus, Perseus, Cassiopeia, Auriga, and Gemini. In the direction of Cygnus is the Great Rift, a band of dark matter that lies along the Milky Way, dividing it into two forks. Another dark region is the Coalsack, in Crux. Once believed to be vast empty regions in space, these dark areas are now known to be clouds of dark matter blotting out the light behind them. Such nonluminous clouds of dust and gas, called dark nebulae, obscure many parts of the sky from sight; in the direction of the galactic center, the view is almost entirely obscured.
The Columbia Electronic Encyclopedia, 6th ed. Copyright © 2012, Columbia University Press. All rights reserved.