One of the mysteries in astrophysics has been the existence of a 511 kev line of emission from the Galaxy's center for some time. The author, Volodymyr Takhistov, proposes that neutron star mergers generate a copious excess of positrons, which then slowly annihilate with electrons producing the observed excess, and signaling the relative rate of mergers in the Milky Way. The energetics fit. SEE: