Sometimes a strange signal comes from the dark and it takes a while to figure out what that signal means. In this case, scientists analyzing high-energy gamma rays emanating from the galaxy's center found an unexplained source of emission that they say is "consistent with some forms of dark matter."
The data came courtesy of NASA's Fermi Gamma-ray Space Telescope and was analyzed by a group of independent scientists. They found that by removing all known sources of gamma rays, they were left with gamma-ray emissions that so far, they cannot explain. More observations will be needed to characterize these emissions, they cautioned.
Scientists aren't even sure what dark matter (which can only be detected through gravitational effects) is made of. One theoretical candidate could be something called Weakly Interacting Massive Particles (WIMPs), which could produce gamma rays in ranges that Fermi could detect.
Also, the location of the radiation at the galaxy's center is an interesting spot, since scientists believe that's where dark matter would lurk since the insofar invisible substance would be the base of normal structures like galaxies.
"The new maps allow us to analyze the excess and test whether more conventional explanations, such as the presence of undiscovered pulsars or cosmic-ray collisions on gas clouds, can account for it," stated Dan Hooper, an astrophysicist at Fermilab and lead author of the study.
"The signal we find cannot be explained by currently proposed alternatives and is in close agreement with the predictions of very simple dark matter models."
An intriguing signal could be due to “dark matter annihilations” pops up on the left of this data gathered by NASA’s Fermi Gamma-ray Space Telescope. The image on left shows the galactic center in gamma rays with energies between 1 and 3.16 GeV. Red indicates the most activity, and the labels are for pulsars. The image at right has all known gamma-ray sources removed. Credit: T. Linden, Univ. of Chicago
The scientists suggest that if WIMPs were destroying each other, this would be "a remarkable fit" for a dark matter signal. They again caution, though, that there could be other explanations for the phenomenon.
"Dark matter in this mass range can be probed by direct detection and by the Large Hadron Collider (LHC), so if this is dark matter, we're already learning about its interactions from the lack of detection so far," stated co-author Tracy Slatyer, a theoretical physicist at the Massachusetts Institute of Technology.
"This is a very exciting signal, and while the case is not yet closed, in the future we might well look back and say this was where we saw dark matter annihilation for the first time."