First Credible Contact with an Alien Space Civilization

The space object we call ‘Oumuamua entered our solar system a year ago, turned and quickly left again. It was represented as a solid cigarlike object but it was not. Now we know it was a thin sheet of 0.3 mm thickness and 16000 sq meter surface. A Harvard paper proposed that it was a light sail from an alien ship. It is the first plausible encounter.