Researchers from Johns Hopkins published a study providing evidence for the theory that mysterious gamma rays emanating from the center of the Milky Way originate from dark matter particles colliding.
This view of the gamma-ray sky constructed from one year of Fermi LAT observations is the best view of the extreme universe to date. The map shows the rate at which the LAT detects gamma rays with energies above 300 million electron volts from different sky directions. Brighter colors equal higher rates. Credit: NASA/DOE/Fermi LAT Collaboration
Steps towards solving decades-long mystery
These gamma rays were first detected in 2009, and their origins have stumped scientists ever since. Some have theorized that the rays came from quickly spinning neutron stars, others that they come from dark matter particles. The study, published Thursday in Physical Review Letters, may provide proof of the latter.
The researchers used supercomputers to create maps that predicted where dark matter should be based on the history of how the Milky Way galaxy formed. When the Milky Way was first formed, smaller systems made of dark matter and other materials entered, becoming the building blocks of the galaxy. The dark matter particles clustered together in the center of the young galaxy, increasing the rate of dark matter collisions.
The scientists’ maps matched actual gamma ray maps made with the Fermi Gamma-ray Space Telescope. The researchers said the gamma rays being observed have the same properties as those that would be produced by dark matter particles colliding.
However, this is not definitive proof. The rays could also be emitted from old neutron stars spinning with a rotational period of less than 10 milliseconds, called millisecond pulsars. The researchers from Johns Hopkins found a flaw in this theory. For this to be true, there would have to be more millisecond pulsars than the number that have been observed.
Energy could be the key
The team is now planning a second experiment that will provide more definitive proof, testing whether the rays have high energy – indicating that they come from millisecond pulsars – or lower energy – indicating that they come from dark matter.
“It’s possible we will see the new data and confirm one theory over the other,” said co-author Joseph Silk, a professor of physics and astronomy at Johns Hopkins, in a press release, “Or maybe we’ll find nothing, in which case it’ll be an even greater mystery to resolve.”
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