3I/Atlas Latest: Astrophysicist Suggests Mysterious Interstellar Object Made From 'Most Efficient Fuel' Out There

A conceptual image of the interstellar comet 3I/ATLAS as it streaks across the night sky--a rare visitor travelling nearly along the plane of the Solar System and unexpectedly brightening as it nears the Sun.

The mystery surrounding interstellar comet 3I/ATLAS has deepened after Harvard astrophysicist Avi Loeb suggested it could be made of antimatter, a substance that annihilates normal matter and releases near-total energy.

Writing on Medium, Loeb called antimatter 'the most efficient fuel' in the universe, arguing that if 3I/ATLAS truly contained it, its passage through the solar wind might generate detectable gamma-ray or X-ray emissions—signals that NASA's Fermi Gamma-Ray Space Telescope could observe. Though he stressed the theory was 'pedagogical,' the claim has reignited debate over whether this cosmic visitor might be more than just another comet.