The Great Annihilator is a system containing two black holes. Great Annihilator A compresses approximately 198 solar masses within 0.0008 solar radii. This is the largest known black hole in the galaxy (not including the supermassive Sagittarius A* at the core).
Great Annihilator B contains about 66 solar masses within 0.003 solar radii. The black holes have five stars orbiting them. The system is located near the galactic core at 360:-43:23000.
The Great Annihilator is one of the brightest gamma-ray sources found in the Milky Way galaxy. It produces massive amounts of pairs of photons at 511 keV, which usually indicates the annihilation of an electron-positron pair (thus, the name). The Great Annihilator also has a radio source counterpart which emits jets that are about three light years long. These jets are probably synchrotron emissions from positron-electron pairs streaming out at high velocities from the source of antimatter.