Galaxy’s gamma-ray glow may expose dark matter

Center of Milky Way produces high-energy radiation that hints at mysterious particles

GAMMA GENERATOR  Gamma-ray emissions from the center of the Milky Way appear as colors other than purple in these images. The panel at right shows that when emissions from known gamma-ray sources are removed, a strong signal about 10,000 light-years across remains. A team of physicists argues that dark matter particles are responsible for those gamma rays.

T. Linden, Univ. of Chicago

SAVANNAH, Ga. — An unexpectedly bright glow of gamma rays at the center of the Milky Way may be the signature of suicidal dark matter, according to a new analysis of observations by NASA’s Fermi Gamma-ray Space Telescope that were reported April 6 at a meeting of the American Physical Society.

Dark matter dominates the mass of galaxies, including our own, but its composition remains a mystery. Many theorists think that dark matter comes in the form of particles that annihilate each other and release energy when they collide. If that’s the case, then galaxies should emit large amounts of high-energy gamma radiation, particularly at their centers where the density of dark matter is greatest.

That’s exactly what a team of astrophysicists led by Dan Hooper from Fermilab in Batavia, Ill., found in Fermi data. After subtracting known sources of gamma rays, such as rapidly spinning dead stars called pulsars, the researchers were left with radiation that is brightest at the Milky Way’s center and extends outward at least 5,000 light-years.

Hooper’s team is not claiming a discovery of dark matter: Unidentified pulsars and other mundane objects could have produced the gamma rays. But the study offers a rare clue in the frustrating quest to understand dark matter.

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