When the first space object from beyond our solar system was discovered from Hawaii last year, there was a lot of playful speculation about whether it was an alien spacecraft.

Extraterrestrials? Storm troopers? Little green men?

Then a volley of scientific studies, including one led by scientists at the University of Hawaii Institute for Astronomy, strongly suggested that ‘Oumuamua, as it would be called, was a natural object — perhaps space debris spit out during the birth of a planet or the death of a star.

Now along comes a new study, published last week by a couple of Harvard University scientists, that speculates that it may have been of alien origin and possibly even “a fully operational probe sent intentionally to Earth vicinity by an alien civilization.”

The Hawaii scientists were not impressed.

“Based on the data that myself and the team here at UH acquired and analyzed, there is no reason to suspect that ‘Oumuamua is anything but a natural object from another solar system,” said researcher Rob Weryk, who first spotted the unusual cigar-shaped object from observations taken from Maui’s Pan-STARRS telescope.

UH professor Karen Meech, who led an international team of scientists that were among the first to examine the interstellar visitor, agreed. She called the Harvard study flawed and said it lacked evidence to support some of its claims.

“I’m frustrated by this paper,” she said in an email.

Writing in The Astrophysical Journal Letters, Harvard Institute for Theory and Computation researchers Shmuel Bialy and Abraham Loeb suggest the object was powered by solar radiation pressure.

The paper rejects assertions that the object is a comet and speculates it is a lightsail that harnessed solar radiation pressure to traverse vast stretches of interstellar space.

“Lightsails with similar dimensions have been designed and constructed by our own civilization, including the IKAROS project and the Starshot Initiative,” the study said.

The paper went on to suggest that the object may have carried cargo between planets or stars but may have been reduced to interstellar space junk.

“Alternatively, a more exotic scenario is that ‘Oumuamua may be a fully opera- tional probe sent intentionally to Earth vicinity by an alien civilization,” the paper said, adding that its unusual speed and shift in trajectory suggest “a targeted probe.”

Meech and Weryk were co-authors of a Nature study with European and UH colleagues in June that declared the object was a comet rather than an asteroid, as it was originally classified.

The study found that ‘Oumuamua experienced an unexpected boost in speed and shift in trajectory as it passed through the inner solar system, which is consistent with the behavior of a typical comet that has jets of gaseous material expelled from its surface.

However, there were no outward signs of such “outgassing” from ‘Oumuamua. There was no evidence of an atmosphere or tail like a comet, according to the paper.

The researchers estimated that ‘Oumuamua’s outgassing may have generated only a small amount of dust — enough to give a speed boost but not enough to be detected — and speculated the dust particles found on the surface of most previous comets had eroded away during ‘Oumuamua’s long journey through interstellar space.

Meech said her team’s paper in Nature analyzed many possible physical mechanisms to explain the accelerated speed.

“We found that cometlike outgassing was a physically viable explanation, despite the lack of visible coma in the images,” she said.

The paper did acknowledge, however, that existing observations could not conclusively determine the exact physical nature of ‘Oumuamua.

The Bialy and Loeb paper does not present good arguments for why solar radiation pressure would be a more plausible explanation for the boost in speed unhindered by gravity, Meech said.

“The assumptions needed for solar radiation pressure to explain the observed nongravitational acceleration are far more exotic than those needed for outgassing with no visible coma. One needs to back extraordinary claims with extraordinary evidence — and they do not do this,” she said.

What’s more, Meech said she doesn’t believe that the sail shape is compatible with the rotational light curves, or pattern of reflected light, observed by different teams of scientists.

“Bialy and Loeb do not investigate whether their hypothesis of a solar sail is consistent with observations. Not only is this a flaw in their paper; I’m very disappointed in the refereeing process that this was not caught,” she said.

Weryk said a lot of unknowns remain about ‘Oumuamua, which is long gone and never to return. To learn more, “we’re hoping to find more objects like it,” he said.

“Now that we know they exist for sure, we’re looking closer at each new near-Earth object discovery that we make with the Pan-STARRS telescope,” he said. “I’m confident that we’ll eventually find another.”