A Harvard University scientist who said a mysterious object that briefly travelled through our solar system in 2017 and 2018 might be an alien spacecraft is standing by his claim.

The approximately 400-metre-long, 40-metre-wide object has been named Oumuamua, from a Hawaiian word meaning messenger from afar arriving first.

It was first spotted in October 2017, moving at an unusually fast speed of more than 87 kilometres per second, and left our solar system three months later.

In addition to its speed, the object attracted attention from stargazers for its peculiar shape and its movement pattern, which was not based on the gravitational pull of the sun or planets.

Abraham Loeb, the chair of Harvard’s astronomy department, co-authored a paper last fall positing that Oumuamua “may be a fully operational probe sent intentionally to Earth vicinity by an alien civilization.”

Loeb and co-author Shmuel Bialy suggested that the object might be a light sail, which could theoretically move through space under the power of light or solar energy.

Their claims were widely questioned by other astronomers. Paul Delaney of York University in Toronto claimed Loeb and Bielay were “reaching a little bit” by suggesting that Oumuamua was created artificially.

“Is it a possibility? Yes. Is it a likely probability? No,” Delaney told CTV’s Your Morning last November.

The scientist who first discovered Oumuamua also distanced himself from Loeb’s theory, calling his comments “wild speculation.”

Loeb does not appear to be backing down In the face of these accusations that he is overpublicizing an idea that is theoretically possible, but realistically improbable.

In an interview with Israeli newspaper Haaretz, Loeb said he wrote the paper because he believed in his conclusions, not in an attempt to get publicity.

“Scientists of senior status said themselves that this object was peculiar but were apprehensive about making their thoughts public,” he said.

Loeb said he could be “committing image suicide” if a more natural explanation for Oumuamua ever surfaces. Still, he held steady in his belief that Oumuamua could be the result of a “fishing expedition” from another solar system – similar to the manmade Voyager probes launched from Earth in 1977.

For its part, NASA says Oumuamua certainly originated in another solar system and may have spent hundreds of millions of years meandering through the Milky Way before arriving in our solar system. It reserves comment on what the object may actually be.

Loeb has also co-authored a new paper, “Turning Up the Heat On Oumuamua,” in which he and another Harvard astronomer attempt to determine how common interstellar objects such as Oumuamua are in our solar system.

According to their model, approximately two objects from outside the solar system pass through Mercury’s orbit annually, and some of those objects crash into the sun at a rate of about one every 30 years.

These objects are typically asteroids and comets, which are understood much better by the scientific community than Oumuamua has been to date.