Asteroids from another solar system found 'hiding in plain sight', scientists say

Most UK adults don't know the name of our galaxy, a survey suggests (Ye Aung Thu/AFP/Getty Images)

A set of asteroids that came from outside our solar system have been hiding in plain sight, according to scientists.

Interstellar visitors such as the comets Oumuamua and 2l/Borisov have caused excitement, in part because they represent the first known times that humanity has been so near to an object from another distant solar system. But a new study suggests that such visitors might have been alongside us all along.

The researchers suggest that the objects came from other stars, billions of years ago, and have been orbiting around our Sun undiscovered ever since.

The objects were first pulled out of another solar system in the relatively early days of the universe, when the stars were closer together and so upset each other's gravity more easily. This enabled asteroids to be pulled from one star system to another," said Fathi Namouni, lead author of the study, in a statement.

Just as with those other visitors, researchers hope they can use the objects to understand the differences between objects that have spent all of their time in our solar system and those alien visitors.

“The discovery of a whole population of asteroids of interstellar origin is an important step in understanding the physical and chemical similarities and differences between solar system-born and interstellar asteroids,” commented Dr. Morais.

The researchers came upon the discovery after running computer simulations that allowed them to look at how the solar system may have looked in its earliest days. When they looked the asteroids in question, they found they were orbiting the Sun in a distant region beyond the disc of gas and dust that would form the rest of the asteroids, and along a different orbit to the other planets and asteroids.

That strange placement led the researchers to speculate that the asteroids were not native at all but had actually been plucked out of interstellar space as the planets were forming.

They have identified 19 asteroids that appear to have come from outside of the solar system. They are now orbiting as part of a larger group called Centaurs, which move around in the space between the giant planets of our solar system and show unusual orbits that often perplex computer simulations designed to model and predict them.