Avi Loeb, a Harvard astrophysicist, has suggested that the interstellar object 3I/ATLAS could be composed of antimatter, a form of material that annihilates ordinary matter and releases nearly total energy on contact.
Antimatter is "the most efficient fuel" in the universe
Loeb proposed this idea in a Medium essay, arguing that the interaction between antimatter and solar particles could explain the object's unusual brightness and apparent acceleration.
According to Loeb, if 3I/ATLAS contains antimatter, its passage through the solar wind might generate detectable gamma-ray or X-ray emissions, which could be observed by NASA's Fermi Gamma-Ray Space Telescope.
Author's summary: Avi Loeb suggests 3I/ATLAS may contain antimatter.