Dark Matter Witnessed After Galactic Collision

By Mark Hoerrner

University of Arizona scientist and astronomer Douglas Clowe is as excited as a kid who’s just found where his parents hide the presents at Christmas. Years of planning and research have paid off, he believes, in the imaging of a collision between two galaxies that occurred over 100 million years in the past. The image shows something—or rather, a nothing—that scientists have debated for 70 years.

Science News Online is reporting that Clowe was able to capture imagery of dark matter, a substance that scientists say holds 90 percent of the universe together. The converse theory is that the universe is held together by a mutated version of the theory of gravity. The problem with the dark matter proposal is that it’s generally invisible, thus preventing scientists from proving its existence and validating their theory.

However, Clowe was able to use multiple telescopes and observatories to capture a violent merging of two galaxies that he says resulted in the appearance of dark matter that was unfettered by the explosive reaction.

"Dark matter particles don't experience the same type of drag that slows down gas clouds," Clowe told Science News.

Gravity works like duct tape for the universe, he says, keeping regular matter and dark matter merged into an existence so close that like Paris Hilton and her miniature dog, science can’t tell where one begins and the other ends. In a galactic collision like the one Clowe witnessed, gases expand and encounter resistance, effectively slowing the movement of both galaxies. Dark matter, however, is unimpeded by the release of force and passes right through. By his estimation, if dark matter didn’t exist, most of the mass from the collision would have accumulated in one spot, but the intrepid scientists witnessed "clumps" of matter scattered throughout the area.

"This proves in a simple and direct way that dark matter exists," says coauthor Maxim Markevitch of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass. "It puts to rest the remaining doubt that cosmologists have had until now."

There are alternative theories, however, that seek to explain what Clowe saw. The models for evaluating the cosmic events are relatively obscure. Michael Turner of the University of Chicago says that Clowe’s discovery is "mind boggling,’ and that it could lead to a host of discoveries about intergalactic collisions such as this.

"It’s kind of like a cosmic centrifuge," he told the Science News.