'Oumuamua, the First Confirmed Interstellar Object

On 19 October 2017 the Pan-STARRS1 telescope in Hawaii detected 1I/2017 U1, named 'Oumuamua, the first object confirmed to have entered the solar system from interstellar space. Its extreme elongation and a non-gravitational acceleration with no detectable cometary outgassing produced four competing published explanations and became one of the named catalysts for the founding of the Galileo Project at Harvard.