A year-long study with a GRO detector has for the first time mapped in detail the distribution of this emission along the plane of the galaxy To the astonishment of astronomers, it also recorded a broad distribution of the same annihilation radiation in a region some 3,000 light-years out from the disk of the Milky Way.
Although the source of the annihilation radiation is debatable, there is no dearth of candidates in the crowded environs of the galactic center.