Gamma-ray evidence for dark matter weakens

A potential sign of dark matter is looking less convincing in the wake of a new analysis.

High-energy blips of radiation known as gamma rays seem to be streaming from the center of the Milky Way in excess. Some scientists have proposed that dark matter could be the cause of that overabundance. Particles of dark matter — an invisible and unidentified substance that makes up the bulk of the matter in the cosmos — could be annihilating in the center of the galaxy, producing gamma rays (SN Online: 11/4/14).

In the new study, scientists scrutinized the latest data from the Fermi Gamma-ray Space Telescope. At the galaxy’s center, the researchers found more gamma rays than they could explain, they report in a paper posted online April 12 at arXiv.org. But, when the researchers compared the region at the center of the galaxy with control regions away from the galaxy’s center — where dark matter signals wouldn’t be expected — they also found spots with more gamma rays than expected.

“What I see in the control regions looks just like what I see in the galactic center,” says astrophysicist Andrea Albert of Los Alamos National Laboratory in New Mexico, one of the researchers who worked on the analysis. So they can’t claim that dark matter is the cause. “That’s a bummer,” she says.