Strange Signal From Galactic Center Is Looking More and More Like Dark Matter
The more that scientists stare at it, the more a strange signal from the center of the Milky Way galaxy appears to be the result of dark matter annihilation. If confirmed, it would be the first direct evidence for dark matter ever seen.
Dark matter is a mysterious, invisible substance making up roughly 85 percent of all matter in the universe. It floats throughout our galaxy, but is more concentrated at its center. There, a dark matter particle can meet another dark matter particle flying through space. If they crash into one another, they will annihilate each other (dark matter is its own antiparticle) and give off gamma rays.
To search for a dark matter signal, astronomers use NASA’s Fermi Gamma-Ray Telescope to map the gamma radiation throughout the galaxy. Then, they try to account for all known sources of light within this map. They plot the location of gas and dust that could be emitting radiation and subtract that signal from their gamma-ray map. Then they determine where all the stars are and subtract out that light, and so on for every object that might be emitting radiation. Once all those sources are gone, there remains a tiny excess of gamma radiation in the data that no known process can account for.
“The more we scrutinize it, the more it looks like dark matter,” said astrophysicist Dan Hooper of Fermi National Accelerator Laboratory, co-author of a paper that appeared Feb. 26 on arXiv, a website that hosts scientific papers that have yet to go through peer-review.