Nowadays it is taken for granted that the Universe contains no substantial amounts of antimatter. Most cosmological models include hypothetical physical processes to explain why matter dominates although the Universe should have been created with equal amounts of both. But in 2018, the Alpha Magnetic Spectrometer 2 (AMS-02) experiment on the International Space Station possibly detected several antihelium nuclei, suggesting that some original antimatter survived to form antistars and even antigalaxies. Now, Simon Dupourqué and colleagues at the Institut de Recherche en Astrophysique et Planétologie (IRAP), France, identify possible antistars based on ten years of gamma-ray observations from the orbiting Fermi Gamma-ray Space Telescope and derive constraints on how many such objects might exist in our solar neighborhood [1].
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