WASHINGTON, Aug. 21 (UPI) -- U.S. astronomers say they have found the first direct proof of the existence of so-called dark matter.
NASA's Chandra X-ray Observatory and other telescopes show dark and normal matter have been wrenched apart by the collision of two large clusters of galaxies.
"This is the most energetic cosmic event, besides the Big Bang, which we know about," said team member Maxim Markevitch of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass.
Astronomers say the observations provide the strongest evidence yet that most of the matter in the universe is dark. Despite considerable evidence for dark matter, some scientists have proposed alternative theories for gravity where it is stronger on intergalactic scales than predicted by Newton and Einstein, removing the need for dark matter. However, such theories cannot explain the observed effects of that collision.
"A universe that's dominated by dark stuff seems preposterous, so we wanted to test whether there were any basic flaws in our thinking," said Doug Clowe of the University of Arizona-Tucson, and leader of the study. "These results are direct proof that dark matter exists."
The study will appear in an upcoming issue of The Astrophysical Journal Letters.
