Positrons are electrons’ mischievous twin—identical in every way except for one crucial difference: they have a positive charge. But while electrons are everywhere, positrons are far rarer, appearing only in high-energy processes before quickly vanishing in a flash of pure energy.
First predicted by Paul Dirac in 1928 and discovered in cosmic rays a few years later, positrons were the first known antiparticles. When a positron meets an electron, they annihilate each other, converting their mass entirely into energy—usually in the form of two high-energy gamma-ray photons. This process, called annihilation, is the reason why large amounts of antimatter don’t naturally exist in our everyday world—any positrons that appear tend to be destroyed almost immediately upon contact with normal matter.
Despite their fleeting nature, positrons show up in some pretty important places. They are produced naturally in beta-plus decay, a type of radioactive decay where a proton in an unstable nucleus transforms into a neutron and emits a positron along with a neutrino. They also important in positron emission tomography (PET scans), a medical imaging technique that detects positrons emitted by radioactive tracers inside the body, helping doctors visualize processes like metabolism and brain activity in real time.
In space, positrons are created in extreme environments, from the interactions of cosmic rays with the atmosphere to the violent regions around black holes and pulsars. Some theories even suggest that dark matter particles might occasionally annihilate into positrons, so they might be a potential clue in the search for new physics.