Fascinating

Some professors at Harvard are suggesting that the 'Oumuamua interstellar object might be some form of space craft:

On October 19th, 2017, the Panoramic Survey Telescope and Rapid Response System-1 (Pan-STARRS-1) in Hawaii announced the first-ever detection of an interstellar asteroid, named 1I/2017 U1 (AKA 'Oumuamua).

In the months that followed, multiple follow-up observations were conducted that allowed astronomers to get a better idea of its size and shape, while also revealing that it had the characteristics of both a comet and an asteroid.

Interestingly enough, there has also been some speculation that based on its shape, 'Oumuamua might actually be an interstellar spacecraft (Breakthrough Listen even monitored it for signs of radio signals!).

A new study by a pair of astronomers from the Harvard Smithsonian Center for Astrophysics (CfA) has taken it a step further, suggesting that 'Oumuamua may actually be a light sail of extra-terrestrial origin.

The study – "Could Solar Radiation Pressure Explain 'Oumuamua's Peculiar Acceleration?", which recently appeared online – was conducted by Shmuel Bialy and Prof. Abraham Loeb. Whereas Bialy is a postdoctoral researcher at the CfA's Institute for Theory and Computation (ITC), Prof. Loeb is the director of the ITC, the Frank B. Baird Jr. Professor of Science at Harvard University, and the head chair of the Breakthrough Starshot Advisory Committee.

The object has been accelerating away from the sun, which might be caused by out-gassing, but there was no out-gassing on the way in, and the object's rotation has not changed, which would normally happen with out-gassing.

Unfortunately, we will never know for sure.