Scientists Offer Proof of 'Dark Matter'

This composite image depicts the "bullet cluster" formed by galactic collision, with hot gas in a bullet shape shown in red and areas of dense matter in blue. Most of the matter in blue area is "dark," according to the astronomers' analysis

For decades, many scientists have theorized that the universe is made up of nearly undetectable mysterious substances called dark matter and dark energy. But until yesterday (22-aug-2006) there was no proof that the subatomic matter actually exists.

After studying data from a long-ago collision of two giant clusters of galaxies, researchers now say they are certain dark matter does exist and plays a central role in creating and defining gravity throughout the universe.

While the scientists are still not sure exactly what dark matter is, since they have yet to identify it in a laboratory, they said that the workings of the universe cannot be explained without it.

The breakthrough came using data from NASA's orbiting Chandra X-Ray Observatory and involved information from what researchers called the most massive release of detected energy in the universe since the big bang.

Scientists said that the "bullet cluster," formed by a collision between an enormous cluster of galaxies more than 3 billion light-years away and a smaller galaxy cluster, demonstrated the existence of dark matter. In effect, the collision stripped the dark matter away from visible matter. Once stripped, dark matter was clearly identified by the strong gravitational pull that it exerted.

The super-hot gases have qualities that typically would have become the seat of any new gravitational fields, cosmologists say, but instead they went with the stars. That could happen, Maxim Markevitch (Team member, Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass., ) said, only if dark matter separated from the gases and collected with the stars.