Gamma-ray excess most likely from dark matter annihilation

Guardian : Since its launch in 2008, the Fermi Gamma-Ray Space Telescope has detected an unexpected surplus of gamma rays coming from the center of the Milky Way. While many believed the gamma rays were caused by the annihilation of dark matter such as weakly interacting massive particles (WIMPs), others argued for more traditional explanations. A new analysis of five years of Fermi data appears to have ruled those options out. Dan Hooper of Fermilab and his colleagues have created a high-resolution map of the gamma-ray signal, which extends outward 5000 light-years from the Milky Way’s center. The map closely matches the predicted dark matter profile for the galaxy, a pattern that would be very difficult for other phenomena to reproduce. Preliminary Fermi data suggest that the gamma-ray signal is also present in the dwarf galaxies orbiting the Milky Way. If that signal is confirmed, it would be the most significant evidence yet for the existence of dark matter.