The object, nicknamed 'Oumuamua, meaning "a messenger that reaches out from the distant past" in Hawaiian, was first discovered in October 2017 by the Pan-STARRS 1 telescope in Hawaii.
In a letter published in The Astrophysical Journal Letters on 12 November, the researchers add that Oumuamua could be a spacecraft pushed along by light falling on its surface.
At first, astronomers thought the rapidly moving faint light was a regular comet or an asteroid that had originated in our solar system. They say it "may be a fully operational probe sent intentionally to Earth vicinity by an alien civilization". The team termed the possible propulsion system a "lightsail of artificial origin".
"This would account for the various anomalies of 'Oumuamua, such as the unusual geometry inferred from its light-curve, its low thermal emission, suggesting high reflectivity, and its deviation from a Keplerian orbit without any sign of a cometary tail or spin-up torques".
The paper, written by Abraham Loeb, professor and chair of astronomy, and Shmuel Bialy, a postdoctoral scholar, at the Harvard Smithsonian Center for Astrophysics, points out that comparable light-sails already exist on earth.
Whether Oumuamua is a light sail from a spacecraft of artificial origin floating aimlessly through solar systems or an operational probe sent intentionally to Earth, the researchers said its likely origin will only be determined by searching for other objects like it in the future.
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?"
"Not 'where is the lack of evidence so that I can fit in any hypothesis that I like?"
He raised questions in particular about the object's tumbling motion.
Scientists have been puzzling over "Oumuamua" ever since the mysterious object was seen tumbling past the sun in late 2017.
"Why send a spacecraft which is doing this?" he said.
Oumuamua has now left the solar system and is no longer visible even with telescopes.
Mr Loeb called his findings "purely scientific and evidence-based" and added: "I follow the maxim of Sherlock Holmes: when you have excluded the impossible, whatever remains, however improbable, must be the truth".