Positrons—the antimatter counterpart of electrons—are created in high-energy cosmic processes. When normal matter meets its antimatter counterpart, they annihilate, or vanish, and produce a distinctive 511 keV gamma-ray signal. Scientists use this signal to detect where these annihilations occur.

Now, 20 years’ worth of this kind of data has revealed that positron annihilations might be happening in unexpected places and at far greater rates than previously thought. The new study, published in Astronomy & Astrophysics, describes how astronomers are interpreting a new positron annihilation map and whether the results represent true annihilations or just imaging artifacts.