Data from a space telescope peering at gamma-ray radiation from the central region of the Milky Way galaxy is the strongest evidence yet of some of it coming from dark matter, NASA says.
Dark matter, the invisible and mysterious substance thought to constitute most of the observable universe, has been the subject of intense studies by astrophysicists since it was first theorized as long ago as 1932 by the Dutch astronomer Jan Oort.
Now, analyzing data from the space agency's Fermi Gamma-ray Space Telescope, U.S. researchers say they've created new maps of the center of our galaxy indicating greater levels of gamma radiation than could be the result of known, observable sources.
The excess emission would consistent with dark matter in some form, they say.
"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," lead study author and astrophysicist Dan Hooper at Fermilab in Batavia, Ill., says. "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."
Gamma-ray sources are common in the center of the Milky way, generated by interacting binary star systems, isolated pulsars, remnants of supernovae and collisions between particles and interstellar gas.
Scientists say it's where they also expect to see the galaxy's greatest concentration of dark matter, detectable only through its interaction with radiation and normal matter through gravity.
While dark matter's true composition remains unknown, a leading candidate is Weakly Interacting Massive Particles or WIMPS, which when they decay would produce gamma ray, the highest-energy kind of light.
When astronomers removed all the known sources of gamma-rays from Fermi galactic center observations, a region of remaining emissions persists at energies billions of times the level of visible-wavelength light, spreading outward from the galactic center for 5,000 or more light-years, NASA reported.
Based on the gamma-ray spectrum, annihilations of particles of dark matter of a certain mass would match the excess, the scientists say.
"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," researcherTracy Slatyer, an MIT theoretical physicist, says. "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."
However, the researchers added, it will require additional sightings and data from other cosmic objects or in LHD studies to validate this interpretation of dark matter.
"Our case is very much a process-of-elimination argument," study co-author Douglas Finkbeiner of the Harvard-Smithsonian Center for Astrophysics says. "We made a list, scratched off things that didn't work, and ended up with dark matter."
