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takyon writes:

Interstellar asteroids found hiding in plain sight

A new study has identified the first known permanent population of asteroids originating from outside our Solar System. The objects are believed to have been captured from other stars billions of years ago, and have been orbiting our Sun in disguise ever since. The work is published in the journal Monthly Notices of the Royal Astronomical Society.

The first interstellar visitor, the asteroid known as 'Oumuamua, hit the headlines in 2017, however it was just passing through. The newly-identified asteroids on the other hand are thought to have been present almost since the birth of our Solar System, 4.5 billion years ago in a star cluster where each sun had its own planets and asteroids.

"The close proximity of the stars meant that they felt each others' gravity much more strongly in those early days than they do today," explained Dr Fathi Namouni, lead author of the study. "This enabled asteroids to be pulled from one star system to another."

Also at ScienceAlert.

An interstellar origin for high-inclination Centaurs (open, DOI: 10.1093/mnras/staa712) (DX)

Original Submission