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Mauna Kea telescope helps find first-ever thread of dark matter

By Los Angeles Times

LAST UPDATED: 12:22 a.m. HST, Jul 5, 2012

Scientists using the  Subaru telescope on Mauna Kea in Hawaii and the XMM-Newton space telescope have found the first-ever filament of mysterious dark matter connecting two galaxies 2.7 billion light-years away.

Dark matter is thought to act as the spider silk for the cosmic web of the universe. 

But although it makes up most of the matter in the universe, scientists had been able to find only clumps of it in the web’s galaxy-filled “nodes,” not along the gossamer threads that are thought to help give the universe its structure.

The discovery, published online Wednesday by the journal Nature, catapults these tendrils from sound theory to observable fact.

“I have to say the evidence is pretty strong,” said Manoj Kaplinghat, a theoretical astrophysicist at the University of California, Irvine, who was not involved in the study. “There have been other claims that have sort of gone away, but this one looks like the best one I’ve seen. As far as I can tell, this really is the first.”

Dark matter, identified in the 1930s, cannot be detected directly because it doesn’t seem to emit or absorb light. But astronomers know it must be there because they see its gravitational effect on the light and visible matter around it. And since there’s about five times more dark matter than normal matter, its gravitational pull has a profound effect on the shape of the universe.

“Dark matter really governs structure formation,” said study leader Joerg Dietrich, an astrophysicist at the University Observatory Munich in Germany. “The galaxy clusters and the filaments are mostly made up of dark matter. The normal matter just follows the distribution of dark matter.”

Previous studies that purported to identify these filaments were later shown to be false or inconclusive.

But Dietrich’s team discovered a rare find: two clusters of galaxies positioned very close to each other on the plane of the sky, making it easier to look for a filament between them.

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