Asteroid immigration from other star systems occurs as the Sun initially formed in a tightly-packed star cluster, where every star had its own system of planets and asteroids.
The close proximity of the stars, aided by the gravitational forces of the planets help these systems to attract, remove and capture asteroids from one another.
Most of the objects in our Solar System, including all of the planets orbit the Sun in the same direction - anticlockwise, but 2015 BZ509 is different, it moves in the opposite direction what known as a 'retrograde' orbit.
"How the asteroid came to move in this way while sharing Jupiter's orbit has until now been a mystery," explains Dr Fathi Namouni, lead author of the study.
"If 2015 BZ509 were a native of our system, it should have had the same original direction as all of the other planets and asteroids, inherited from the cloud of gas and dust that formed them", she added.
To trace the location of the asteroid, the team ran simulations back to the birth of our Solar System - 4.5 billion years ago when the era of planet formation ended.
The result shows that 2015 BZ509 has always moved in this way, and so could not have been there originally and must have been captured from another system.
The discovery of an interstellar asteroid in our own star system has provided a great opportunity to the researchers to understand the evolution of early solar system.
Studying exactly how and when 2015 BZ509 settled in Solar System could offer us clues about the Sun's original stellar nursery and about the potential enrichment of our early environment with components necessary for the appearance of life on Earth.
Image Credit: NASA/JPL-Caltech
Original Source: Royal Astronomical Society
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