spacetoday.net: Chandra data bolsters dark matter

Posted: Mon, Oct 28, 2002, 8:09 AM ET (1309 GMT)
Chandra image of NGC 720 dark matter (NASA)

Observations of a distant galaxy by the Chandra X-Ray Observatory have offered new support for the dark matter model by providing evidence against an alternative explanation. Chandra observations of NGC 720 showed that the galaxy in enveloped by a cloud of hot gas that is flattened relative to the shape of the galaxy. This flattening cannot be explained by an alternative to dark matter called Modified Newtonian Dynamics, which modifies gravity where forces are very small. The flattening can be explained, though, if the galaxy is surrounded by an egg-shaped halo of dark matter, five to ten times as massive as the galaxy itself. Astronomers believe the dark matter is of the "cold" variety, composed of slowly-moving particles that interaction with normal matter only through gravity.