In 2008, satellites detected an unexpectedly large presence of high-energy positrons in our neighborhood of the galaxy. These positrons—antimatter particles with the same mass as an electron, but with a positive charge—have since puzzled scientists with the cosmic mystery of their origins.
Researchers have proposed several possible sources of the positrons. They might be coming from pulsars—massive stars that have collapsed and exploded, spinning and throwing off electrons, positrons, and other matter. Or, they might be coming from something more complex and exotic: dark matter.