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Dark matter eldorado

Nearby galaxy holds record for densest concentration of mysterious mass

Darth Vader and other rulers of the dark side have reason to celebrate. Observations confirm that a faint group of stars in the Milky Way’s backyard has the highest density of dark matter — the invisible material thought to account for 83 percent of the mass of the universe — of any galaxy known.
   
The findings, reported online July 28 at arXiv.org by Joshua Simon of the Carnegie Observatories in Pasadena, Calif., along with Marla Geha of Yale University and their colleagues, provide a bonanza for astronomers trying to unveil the nature of dark matter.

When astronomers discovered the galaxy Segue 1 in 2007, they weren’t sure if it was anything more than a cluster of stars, perhaps stripped from the nearby Sagittarius dwarf galaxy. But observations with the Keck II telescope atop Hawaii’s Mauna Kea now confirm the status of Segue 1 as a galaxy by showing that its stars have a diverse chemical composition, Simon says. 

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