spacetoday.net: Astronomers find direct evidence for dark matter

Posted: Wed, Aug 23, 2006, 8:15 AM ET (1215 GMT)

Astronomers using the Chandra X-Ray Observatory and other telescopes have found what they call "direct evidence" to support the existence of the mysterious dark matter that makes up most of the mass of the universe. Astronomers announced Monday the discovery, based on observations of the galaxy cluster 1E0657-56, which features a bullet-shaped cloud of gas created by a collision with a smaller cluster. Astronomers compared the location of the gas seen in the x-ray images with gravitational lensing of more distant galaxies seen by other telescopes, caused by the overall mass of the cluster. They found that while the gas cloud was slowing down by a drag force in the aftermath of the collision, the dark matter causing the lensing was not slowing down, causing a detectable separation between the dark and normal matter. The finding, while providing new evidence that dark matter exists, doesn't provide any new insights on the composition of dark matter.