NASA Establishes Direct Proof of Dark Matter
Dark matter and normal matter have been wrenched
apart by the tremendous collision of two large clusters of galaxies. The
discovery, using NASA’s Chandra X-ray Observatory and other telescopes,
gives direct evidence for the existence of dark matter.
Dark matter and normal matter have been wrenched apart by the tremendous collision of two large clusters of galaxies. The discovery, using NASA’s Chandra X-ray Observatory and other telescopes, gives direct evidence for the existence of dark matter.
These 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 this 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 at Tucson, and leader of the study. “These results are direct proof that dark matter exists.”
The hot gas in this collision was slowed by a drag force, similar to air resistance. In contrast, the dark matter was not slowed by the impact, because it does not interact directly with itself or the gas except through gravity. This produced the separation of the dark and normal matter seen in the data. If hot gas was the most massive component in the clusters, as proposed by alternative gravity theories, such a separation would not have been seen. Instead, dark matter is required.
“We’ve closed this loophole about gravity, and we’ve come closer than ever to seeing this invisible matter,” Clowe said.
As usual, the folks at Chandra and Harvard provide a number of terrific images and animations of their studies. Worth looking at — as is the whole press release.
Posted: Tue - August 22, 2006 at 07:19 AM