The object was discovered previous year with the Pan-STARRS 1 telescope atop Haleakalā on Maui and was given the Hawaiian name ʻOumuamua, meaning 'a messenger from afar arriving first'.
It was moving at 59,030mph when it was first tracked by scientists.
Harvard scientists have raised the possibility that "Oumuamua", a mysterious cigar-shaped interstellar object, the first of its kind found in our solar system, could have come from an alien civilisation.
The researchers noted in a pre-print of the article that it was an "exotic scenario", but that "Oumuamua may be a fully operational probe sent intentionally to Earth vicinity by an alien civilization".
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 goal.
Oumuamua was dubbed an "interstellar object" when scientists decided it was neither an asteroid or a comet; while comets can speed up in a process known as "outgassing", the shape lacked the cloud of dust that surrounds a melting comet. The team termed the possible propulsion system a "lightsail of artificial origin". One such project, Breakthrough Starshot, is aiming to send hundreds of tiny, lightsail-operated probes to a nearby solar system next year.
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Not all shells are the same, and similarly only a fraction of the interstellar objects might be technological debris of alien civilizations.
It "may be a fully operational probe sent intentionally to Earth vicinity by an alien civilization", states a paper by two Harvard scientists to be published November 12 in The Astrophysical Journal Letters.
In their paper, the Harvard scientists say the only way to know for sure is to keep watch and see what else shows up in our solar system.
Coryn Bailer-Jones, an astronomer at the Max Planck Institute for Astronomy in Heidelberg, Germany, said: "In science, we must ask ourselves 'Where is the evidence?"
But SETI senior astronomer Seth Shostak said in an email to NBC that "one should not blindly accept this clever hypothesis when there is also a mundane explanation for 'Oumuamua - namely that it's a comet or asteroid from afar". "The approach I take to the subject is purely scientific and evidence-based".
But Harvard's research team says they're not giving up hope that it's a sign of alien life: they "follow the maxim of Sherlock Holmes: When you have excluded the impossible, whatever remains, however improbable, must be the truth".