Have astrophysicists finally managed to find elusive dark matter?

Contributed by
Dec 17, 2012

Though it's been theorized for nearly a century, dark matter is better known to many as the stuff of science fiction, not actual science. But researchers continue to work to change that, and now a group of astrophysicists think they've found the strongest evidence yet that dark matter is real.

Using four years of data from the Fermi Gamma-Ray Space Telescope orbiting Earth, scientists at the University of California at Irvine have just released a study theorizing that gamma radiation detected at the center of our Milky Way Galaxy is evidence of the presence of dark matter there. But how do gamma rays equal dark matter?

The theory goes that dark matter is made of WIMPs ("weakly interacting massive particles"), which act as their own antiparticles. When a large number of WIMPs are gathered close together, they begin to destroy each other, producing energy that then generates other particles, which then generate gamma rays. So, if the theory's correct, a large amount of gamma radiation in a concentrated with no other obvious source is a sign of dark matter, and the UC Irvine team believe that's just what they've found.

"It's definitely something new and shining in the gamma-ray there, and it's not attributable to the existing sources in the catalog," said Kevork Abazajian, a UC Irvine astrophysicist who co-authored a paper on the discovery.

But now that Abazajian and his colleague Manoj Kaplinghat have put their findings out there, they and other scientists around the world have to keep trying to prove the discovery isn't just some aberration in the center of the galaxy.

"Definitely, definitely, there is a source," Abazajian said. "This is definitely not just a fluctuation."

But could the source be something other than dark matter? One theory is that the gamma rays actually come from dense stars called pulsars, and even Abazajian acknowledges that's a possibility.The work now will be ruling something like that out.

"I think it could be a very big finding," Abazajian said. "When I came across this, I was like, 'Holy cow, this is so consistent with the dark matter interpretation in many ways.' But until you can rule out the astrophysical potential sources for something similar, it's not going to be a smoking gun."

So what do other astrophysicists outside the study think? Opinion is mixed, and though skeptics appreciate the work that's been done so far, they're hoping for more proof.

"I can only emphasize that it is very difficult to disentangle all the different contributions to the observed data in this region of the sky, and I think more work needs to be done to make a definitive statement," said Simona Murgia, a fellow UC Irvine astrophysicist.

To prove that they're right about dark matter in the center of the Milky Way, Abazajian and Kaplinghat will have to look elsewhere for similar gamma ray evidence, namely in the center of the dwarf galaxies orbiting the Milky Way. Though previous studies have turned up nothing in that area, Abazajian thinks it's worth a look.

"The real smoking gun to show if this is dark matter annihilation or not is to look deeply at these low background sources and see if you see this signal or not," he said. "If you were able to see the same rate, spectrum or morphology in several sources, that would be a real abundance of evidence."

(Via Huffington Post)

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