A Manhattan-sized interstellar object currently streaking through the inner solar system has shown unusual acceleration and an unexpected blue hue — both potential indicators of artificial propulsion, according to Harvard astrophysicist Avi Loeb.

The object, known as 3I/ATLAS, was recorded by NASA spacecraft this week exhibiting non-gravitational acceleration — movement that cannot be fully explained by the pull of the Sun or planets. Typically, such motion would suggest that the object is venting gas and dust, like a comet. But Loeb says the data raise a different, more provocative possibility.

“Alternatively, the non-gravitational acceleration might be the technological signature of an internal engine,” Loeb wrote in a Medium post on Friday. “This might also explain the report on 3I/ATLAS getting ‘bluer than the Sun.’”

He added that the effect could also have natural explanations — such as solar heating or chemical outgassing — but said the color change and acceleration pattern “deserve open-minded investigation.”

NASA’s solar-orbiting observatories recorded a rapid brightening of 3I/ATLAS as it swung within 172 million miles of the Sun earlier this week. Because Earth was on the far side of the Sun at the time, ground-based telescopes were unable to observe the object directly.

However, spacecraft operated by the U.S. Naval Research Laboratory captured measurements showing the object had become “distinctly bluer than the Sun,” according to a newly released paper. The finding is “very surprising,” Loeb noted, since earlier observations showed the object shifting from red to green — but never blue.

Loeb suggested that the color change could point to a hot energy source or reflective surface, potentially consistent with “an artificial engine or illumination.”

If 3I/ATLAS were a natural comet, scientists would expect it to lose nearly half its mass through outgassing in the coming months, producing a large plume of debris visible from Earth. Its failure to do so, Loeb said, could be a sign that “something else” is powering the object.

“If we do not observe a massive cloud of gas around 3I/ATLAS in December,” Loeb wrote, “it could indicate a propulsion system.”

The object’s unique trajectory — slicing through the solar system from interstellar space before exiting again — will bring it closest to Earth on December 19, at a distance of roughly 167 million miles. That will provide researchers their best opportunity to determine whether 3I/ATLAS is an ordinary comet or something far more extraordinary.

NASA officials, however, have been quick to downplay speculation that the object could be extraterrestrial.

“NASA’s observations show that this is the third interstellar comet to pass through our solar system,” said Acting Administrator Sean Duffy — who also serves as U.S. Transportation Secretary — in a post on X responding to a question from reality television star Kim Kardashian.

“No aliens. No threat to life here on Earth,” Duffy wrote.

Still, Loeb criticized NASA for withholding images of 3I/ATLAS taken by the Mars Reconnaissance Orbiter’s HiRISE camera during its early October flyby. Sources told The Post that those images will not be released until after the federal government reopens.

3I/ATLAS is the third known interstellar object to enter our solar system, following 2017’s ‘Oumuamua — which Loeb famously argued could also have been artificial — and 2019’s 2I/Borisov, a confirmed comet.

As with its predecessors, 3I/ATLAS’s behavior has defied expectations, showing properties that some scientists say push the limits of known natural explanations.

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