(MENAFN) A large interstellar comet, designated 3I/ATLAS and first observed this summer, has displayed unusual acceleration not caused by gravity and appeared to turn blue as it passed near the Sun, scientists report.

Astrophysicist Avi Loeb of Harvard University said data from NASA indicates that the comet’s acceleration is likely driven by gas escaping from its surface. He noted that 3I/ATLAS could lose roughly half its mass in the coming months, potentially leaving a significant trail of debris.

Currently, the comet is positioned behind the Sun, preventing ground-based telescopes from observing it. It is expected to become visible again in early December, when direct observations from Earth can resume. In the meantime, NASA and international partners, including the European Space Agency (ESA), continue to monitor the comet using spacecraft instruments.

Loeb suggested that if the comet shows no mass loss upon its return, "the non-gravitational acceleration might be the technological signature of an internal engine."

However, NASA’s Acting Administrator Sean Duffy dismissed this notion, stating on social media that "@NASA's observations show that this is the third interstellar comet to pass through our solar system. No aliens. No threat to life here on Earth."

Loeb also pointed to research indicating that intense evaporation may explain the comet’s unusual blue hue. He wrote: "For a natural comet, this blue color is very surprising," and added that it "could potentially be explained by a hot engine or a source of artificial light," while also noting it may simply be the result of ionized carbon monoxide from a natural object.

3I/ATLAS made its closest approach to the Sun on October 30. ESA confirmed that its Juice spacecraft would observe the comet again on November 2 and 25. The comet is expected to pass nearest to Earth on December 19, offering scientists an opportunity to determine whether it is a natural body or an artificial object.

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