A dwarf galaxy orbiting the Milky Way is filled with gamma rays, pushing scientists to believe that it can be filled with particles of dark matter.
Dark matter is believed to account for 85% of the mass of the entire universe. Looking at the rotation of galaxies and the interaction of clusters of galaxies, we can observe how invisible matter exerts a powerful gravitational attraction in local space. But since dark matter does not interact with ordinary matter through electromagnetic forces, it cannot be seen and therefore its nature remains very mysterious.
According to one of the leading theories, the source of dark matter is weakly interacting massive particles. But these particles have not yet been detected.
Weakly interacting massive particles, when they collide, destroy each other. One of the by-products of this energy annihilation is a burst of gamma rays. But simply scanning space for sources of gamma rays is a difficult task, since there are many other phenomena that also generate gamma radiation.
This dwarf galaxy comes to us here. Known sources of gamma rays are black holes and pulsars, making the task of finding dark matter almost unreal. But ancient dwarf galaxies are known to have a large number of these sources, making them a key place to search for dark matter.
Located just 98,000 light-years from Earth, the Grid 2 galaxy is one of the closest dwarf galaxies found today and the place to look for dark matter. Based on the analysis of data collected by NASA's Fermi gamma telescope Fermi, scientists Alex Goering-Samet and Matthew Walker realized that Grid 2 generates gamma rays in much larger volumes than any other gamma-ray source.
"Something in this dwarf galaxy emits gamma rays," said Goering-Samet, the lead author of the study. "There are no conventional sources of gamma rays, so this is a potential signal of dark matter."
“Gravitational detection of dark matter tells us very little about the behavior of dark matter particles,” said Walker. "But now we can at least watch how dark matter behaves."
