3I/ATLAS alien ship engine in overdrive? Harvard scientist claims interstellar comet is driven by ‘non-gravitational’ acceleration; here’s what he said after the comet reached closest to the sun

Ever since 3IATLAS, an interstellar comet, was discovered, Harvard astrophysicist Avi Loeb has been keenly observing it, and he has also made multiple observations about it. Loeb, who has claimed that there is a 40% chance the comet is alien technology, has now said that the the non-gravitational acceleration of the comet might be due to an internal engine which is driving it.

“Alternatively, the non-gravitational acceleration might be the technological signature of an internal engine,” Loeb said in his latest blog. This comes after Loeb accused NASA of withholding critical information about the interstellar object. Earlier, he had also claimed that the Manhattan-sized interstellar comet could have extraterrestrial origins.

The interstellar comet 3I/Atlas was discovered by NASA’s ATLAS telescope on July 1, 2025. It is the third observed interstellar object to ever enter our solar system.

3I/ATLAS getting bluer than the sun?

Citing research on 3I/ATLAS named “Rapid Brightening of 3I/ATLAS Ahead of Perihelion” by Qicheng Zhang and Karl Battams, the Harvard scientist, in his blog, said that the interstellar object is getting bluer than the sun. He further said, “For a natural comet, this blue color is very surprising. Dust is expected to redden the scattered sunlight, and the surface of 3I/ATLAS is expected to be ~20 times colder than the 5,800 degrees Kelvin at the photosphere of the Sun, resulting in it having a redder color than the Sun.”

“The blue appearance at perihelion is a ninth anomaly in the list of unexpected properties of 3I/ATLAS (compiled most recently here). It could potentially be explained by a hot engine or a source of artificial light,” he added. Loeb said that 3I/ATLAS displayed the first evidence of a non-gravitational acceleration by the date of its perihelion.

Perihelion for 3I/ATLAS reportedly took place on October 30, 2025 when the interstellar interloper was around 1.35 astronomical units (125 million miles, or 202 million kilometers) from the sun (One astronomical unit is the average Earth-sun distance about 93 million miles, or 150 million km.). Perihelion is the point in an object's orbit where it is closest to the sun.