What did we learn from the interstellar object 'Oumuamua?

The answer

1I/'Oumuamua, detected on October 19, 2017, by the Pan-STARRS telescope in Hawaii, was the first confirmed interstellar object passing through our solar system. Its highly hyperbolic trajectory proved it originated beyond our solar system. The 100-400 meter object exhibited puzzling characteristics: an extreme elongated shape (at least 6:1 ratio), no visible coma or outgassing despite passing close to the Sun, and a non-gravitational acceleration as it departed that couldn't be explained by solar radiation pressure alone. Harvard astronomer Avi Loeb controversially proposed it could be an alien light sail, while others suggested it was a nitrogen ice fragment from a Pluto-like exoplanet or a hydrogen iceberg. A 2023 Nature paper by Jennifer Bergner and Darryl Seligman proposed that molecular hydrogen, produced by cosmic ray irradiation of water ice, outgassed and produced the observed acceleration without visible emissions. 'Oumuamua left our solar system too quickly for detailed study, motivating the ESA's proposed Comet Interceptor mission for future interstellar visitors.