1I/2017 U1 is the official name of Oumuamua, an interstellar object which was spotted through the Pan-STARRS telescope in 2017. The object is mysterious. Researchers simply don’t know what it was. It’s the first interstellar object humans have ever seen. It’s likely that the object was quite thin and no longer than 1 kilometre. That means it’s very small in the context of the universe, but quite big in the context of human history.