Oumuamua: The First Interstellar Visitor Still Defying Explanation

In 2017, the first confirmed interstellar object, Oumuamua, passed through the Solar System on a hyperbolic path and showed a tiny non-gravitational push without a visible tail. Natural explanations (e.g., venting hydrogen or nitrogen ices) exist, and Avi Loeb's artificial-origin idea remains controversial; since then Borisov and ATLAS behaved like comets, but Oumuamua remains an unresolved puzzle, underscoring data limits and the hope that Rubin Observatory will help settle what it could not.