A Harvard professor believes that we were visited by an alien object in 2017. In his upcoming book, "Extraterrestrial: The First Sign of Intelligent Life Beyond Earth," theoretical physicist Avi Loeb lays out his theory about a peculiar-shaped object that entered our solar system several years ago. The interstellar object-named "Oumuamua"-was first observed through the Pan-STARRS telescope at Hawaii's Haleakala Observatory in 2017. Researchers determined that it came from a star in the Lyra constellation that is about 25 light-years away from our planet. While many believe it was just a comet, Loeb, the chairman of Harvard University's astronomy department, says there are two major factors that suggest Oumuamua was a piece of alien technology. The first is its cigar-like shape which isn't typical for a natural space object. But the big one was the fact that the object pushed away from the sun. Loeb says the sun's gravitational force would cause a natural object to move faster as it approaches. Loeb points out that this didn't occur with Oumuamua, which accelerated "slightly, but to a highly statistically significant extent" as it moved further and further away. His book hits shelves on January 26.