Harvard astrophysicist Avi Loeb suggests that the interstellar object 3I/ATLAS could be composed of antimatter, a form of material that releases nearly total energy on contact with ordinary matter.
Antimatter is "the most efficient fuel" in the universe
Loeb's idea, presented in a Medium essay, proposes that the interaction between antimatter and solar particles could explain the object's unusual brightness and apparent acceleration.
Loeb wrote,
If 3I/ATLAS truly contained it, its passage through the solar wind might generate detectable gamma-ray or X-ray emissions
Author's summary: Avi Loeb proposes 3I/ATLAS contains antimatter.