National Geographic News, Reporting Your World Daily

Wednesday, July 23, 2008

Photo: Dark Matter Proof Found, Scientists Say


Email to a Friend	<< Back to Full Story

A team of researchers has found the first direct proof for the existence of dark matter, the mysterious and almost invisible substance thought to make up almost a quarter of the universe.

In this composite image, two clusters of galaxies are seen after a collision. Hot gas, seen in red, was dragged away from the galaxies during the collision. That gas makes up more than 90 percent of the mass of normal, or visible, matter. But most of the mass—and thus matter—is located in the galaxy portions of the clusters, shown in blue, scientists say.

In other words, the bulk of visible matter in the clusters has been separated from the majority of mass—which therefore must be dark matter.

X-ray: NASA/CXC/CfA/M.Markevitch et al.; Optical: NASA/STScI; Magellan/U.Arizona/D.Clowe et al.; Lensing Map: NASA/STScI; ESO WFI; Magellan/U.Arizona/D.Clowe et al.