Its flattened, elongated shape and the way it accelerated on its way through the Solar system, distinguished him from ordinary asteroids and comets.
Shmuel Bialy and Abraham Loeb, two astronomers from the Harvard Smithsonian Centre for Astrophysics, suggested the cigar-shaped object - given the Hawaiian name 'Oumuamua, which NASA notes "means a messenger from afar arriving first" - could have been a discarded light sail of extra-terrestrial origin, perhaps sent here on objective.
Since its discovery, scientists have found themselves puzzled due to the unusual features of the interstellar object.
An artist's depiction of Oumuamua, an interstellar object that astronomers believe is a comet, not an asteroid.
Going forward, the researchers believe we should search for other interstellar objects in our sky.
Bialy and Loeb are serious about the possibility Oumuamua might have been deliberately constructed by extraterrestrials.
Despite the Harvard researchers' work, most scientists, NBC News says, are urging caution in assuming there's any other civilization beyond Earth's atmosphere - and that it's actively seeking us out.
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On its face, the study is trying to reconcile 'Oumuamua's pattern of acceleration, which matches that of a comet, to other observations that suggest it's not an active comet.
The scientists sought to explain quirks in Oumuamua's movement by calculating whether it could be powered by the sun's radiation.
The mysterious radio signal was later determined to be coming from Earth, the repeating fast radio bursts are still being investigated, and new research suggests that Tabby's Star is flickering because of dust - rather than being an alien megastructure.
Some are not so sure the cigar-shaped 'Oumuamua is a solar sail, however.
"The thing you have to understand is: scientists are perfectly happy to publish an outlandish idea if it has even the tiniest *sliver* of a chance of not being wrong", Katherine Mack, an astrophysicist, wrote on Twitter.
Of course, the pair aren't claiming that Oumuamua's definitely of alien origin.
Oumuamua has now left the solar system and is no longer visible even with telescopes.
That means the object would be made of some thin material that could absorb radiation from the sun - either a naturally created material we've never seen before, or something made by aliens. "It is impossible to guess the goal of Oumuamua without more data".