Milky Way May Produce Far More Antimatter, Study Finds Extrgalactic Positron Signals

Researchers Thomas Siegert of the University of Würzburg (Germany) and Hiroki Yoneda of Kyoto University (Japan) analyzed the complete dataset from ESA’s INTEGRAL gamma‑ray telescope, collected between 2002 and 2025. They report the first possible detection of positron‑electron annihilation signatures outside the Milky Way, observed in two extragalactic structures – the high‑velocity gas cloud Complex C and the Magellanic Stream.

If the signals are confirmed, they would imply that a significant fraction of the positrons generated inside the Milky Way can escape the galactic disk before slowing down and annihilating. This would raise estimates of the galaxy’s overall antimatter production well above current models, deepening the long‑standing mystery of the excess 511 keV gamma‑ray emission observed toward the Galactic centre.