Investigating the Antimatter Excess

Every particle has an antimatter partner - a particle with the same mass, but opposite charge. In 2008, several space-based experiments observed an excess of anti-electrons, known as positrons, orbiting above the Earth's atmosphere. Ever since, it's been a mystery where the positrons came from: where they produced in decays involving Dark Matter, the invisible substance that has perplexed scientists for decades? Or were they emitted by nearby astronomical objects known as pulsars? The High Altitude Water-Cherenkov Gamma Ray Observatory in Mexico has just shed some light on the matter...