Excess of positrons in space may be indication of dark matter

Science : An excess of positrons has been detected by the Alpha Magnetic Spectrometer (AMS), which collects cosmic rays from its perch on the International Space Station. Although cosmic rays are composed of many different types of particles, including positrons, the increase noted by the AMS could be an indication of the presence of dark matter, according to Samuel Ting of MIT and colleagues, whose study appears in Physical Review Letters. They base their findings on the fact that the usual sources of positrons, such as supernova explosions, produce far more electrons than positrons. Dark-matter collisions would shift that balance. However, other astrophysicists disagree, saying there are many other potential sources, such as pulsars or the interactions of primary cosmic rays from supernova remnants with the interstellar medium. More data will be needed to narrow down the source.