Gamma-ray excess near the Galactic center
Credit: NASA/DOE/Fermi LAT Collaboration and T. Linden (Univ. of Chicago)

The Death of Dark Matter?

We are living in a material world, and we are material people made of normal atoms. But the material Universe as a whole is constructed from mysterious stuff called dark matter, which is nearly five times more abundant than the more familiar stuff we're made out of. Disturbingly, we do not know exactly what dark matter is - the only characteristics we've identified is that dark matter gravitates, but evidently generates no electromagnetic radiation. Our best guess is that dark matter is some form of subatomic particle which has not yet been identified. If dark matter really is some type of subatomic particle, though, it should also have an anti-particle partner. And when a particle meets its anti-particle, the combined matter of the particles is converted into energy according to Einstein's famous equation, E = mc2. Because even a tiny bit of matter contains an enormous amount of energy, this particle/anti-particle annihilation produces very high energy Gamma-ray radiation, which in principle could be detected by Gamma-ray space observatories like the Fermi Gamma-ray Space Telescope. But where to look? Simulations suggest that one of the best places to look for a dark matter annihilation Gamma-ray signal might be the center of our own Galaxy. The image above shows a Gamma-ray image of our Galaxy (from the Large Area Telescope on Fermi), where the bright Gamma-ray emission from the plane of the galaxy stretches from left to right in the image, and the center of the Galaxy lies at the center of the image. The Gamma-ray emission from the Galactic center is a complicated jumble of emission from many sources. The inset shows an attempt to remove the emission from all of these sources, and, once this is done, what's left is an apparent excess of Gamma rays (shown in red and green) arising from the center of the Galaxy. It's possible that this emission comes from some unidentified but more common source (like unresolved emission from faint stars), but it may be that we're seeing the death of dark matter near the center of the Milky Way.
Published: December 17, 2018

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Page Author: Dr. Michael F. Corcoran
Last modified Monday, 17-Dec-2018 08:20:37 EST