This mysterious object, spotted tumbling through our solar system previous year, may have been an alien spacecraft sent to investigate earth.
The object's flat, elongated shape and reddish colour is from outside our solar system, according to the researchers.
"I've been saying for years that the only thing that could happen that would make this more insane and I don't think anybody would blink, is if all of a sudden an alien spacecraft appeared above Earth", he added.
"I welcome other proposals", Loeb added, "but I can not think of another explanation for the peculiar acceleration of Oumuamua".
The Harvard team suggests that Oumuamua could have had a "light sail" feature that created power and energy from light "falling on its surface".
"Oumuamua deviates from a trajectory that is exclusively dictated by the Sun's gravity".
"It is impossible to guess the goal behind Oumuamua without more data", Loeb was quoted as saying. "This could have been the result of cometary outgassing, but there is no evidence for a cometary tail around it".More news: India gets U.S. waiver for development of strategic Chabahar Port in Iran
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The cigar-shaped rock is now speeding through the galaxy and is the first known interstellar object to enter our solar system.
"Recent observational and theoretical studies imply that 'Oumuamua is not an active comet", the researchers said in a draft version of their study.
"Once these data are obtained and analysed, astronomers may know more about the origin and possibly composition of the object".
"Not 'where is the lack of evidence so that I can fit in any hypothesis that I like?" Others derided the paper as attention-seeking and damaging for the entire field.
"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", she wrote on Twitter.
'But until every other possibility has been exhausted dozen times over, even the authors probably don't believe it'.
"Two very capable, very bright astronomers, from a very credible organization, Harvard, have come out with the notion that Oumuamua could be alien in origin", Diamond said.
"Any functional spacecraft would nearly certainly retract its solar sail once in interstellar space to prevent damage", Mr Jackson said. "What they have said is there is interesting and unusual and anomalous behaviour which could potentially be explained by it being an alien spacecraft".