BOSTON – A Harvard astrophysicist has revealed the exact date a mysterious “interstellar object” is set to reach our planet. Professor Avi Loeb has been monitoring what he has dubbed an “alien probe” since its discovery on July 1.

Loeb has proposed that this interstellar traveller, designated 3I/ATLAS, could be carrying surveillance equipment or even weaponry.

“It may come to save us or destroy us. We’d better be ready for both options,” the professor said.

MATTHEW HOPKINS/UNIVERSITY OF OXFORD | PICTURED: Red lines showing the estimated orbits of 3I/ATLAS, and yellow lines show the Sun’s in the Milky Way

And according to his calculations, any potential encounter would occur within a narrow window spanning November 21 to December 5 this year, GBNews reports.

The professor bases this timeline on the object’s trajectory, noting it will pass behind the sun from Earth’s vantage point this October.

3I/ATLAS is on a “retrograde path,” traveling in the other direction to our solar system’s natural flow while staying on Earth’s orbital plane.

The Harvard scientist has claims that there is only a 0.2 per cent probability of such a trajectory occurring naturally.

The object measures some 12 miles across, making it exceptionally large for an interstellar visitor.

And Loeb has compared a potential encounter to “Iran’s air defences when US B-2 bombers appeared: Silent, unstoppable, and overwhelmingly powerful.”