Alien Spacecraft Coming To Earth? Harvard's Avi Loeb Says It's Possible ⁘ NBC Ne...

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NASA is tracking a mysterious, fast-moving object entering our solar system, raising questions about whether it's just a comet — or possibly something more advanced.

Scientists estimate its size could range from the length of Boston's Ted Williams Tunnel, or 1.6 miles, to as long as Manhattan's diameter, about 14 miles across.

"From images, we also saw that this object is active, which means that around the nucleus, there is some coma, which is an indication that this object is, in fact, a comet," explained NASA navigation engineer Davide Farnocchia.

A Hubble Space Telescope image captured in July shows a glow coming from the object in an unusual direction, said Dr. Abraham "Avi" Loeb , director of Harvard's Institute for Theory and Computation.

"It shows a glow ahead of the object, not behind it," he said.

"If it were a standard comet, we would expect some dust to be shed off the surface of the object, and the dust will be pushed behind the object as a result of the solar radiation pressure."

Loeb has written about the object on his blog — even developing a probability scale to weigh the chances that it may not be a natural object.

"This object is unprecedented because of its inferred size, and its inferred trajectory, which is quite fine-tuned to be in the plane of the planets around the sun," he said.

For now, scientists are treating 3I-ATLAS as a comet. Its trajectory is expected stay away from Earth, passing by Jupiter, Mars and the sun before missing our planet by 170 million miles.