Found: lone asteroid expelled from early Solar System

An asteroid ejected from our infant Solar System found refuge billions of kilometres away, beyond the orbit of Neptune, where it has now been spotted, astronomers said Wednesday.

The curious loner is the first carbon-rich asteroid ever observed in the far-flung region called the Kuiper belt, which is filled with frozen objects, a team reported in The Astrophysical Journal Letters.

Its composition suggests the asteroid must have been formed in the inner Solar System, likely in the asteroid belt between Mars and Jupiter, before migrating to its outer reaches, said the team.

This makes it “a relic of the primordial Solar System”, they added.

Theoretical models of our early Solar System describe a tempestuous time with gas giant planets on the rampage, ejecting small rocky bodies from its the system’s centre to far-flung orbits.

Such models suggest the Kuiper Belt should contain a small number of rocky bodies, perhaps also carbon-rich asteroids.

The new observation, using telescopes of the European Southern Observatory in Chile, provides “strong support for these theoretical models of our Solar System’s troubled youth,” said an ESO statement.

The asteroid was spotted partly because it reflects light differently than other objects in the Kuiper Belt, which are icy while asteroids are rocky.

“It looked enough of a weirdo for us to take a closer look,” said study lead author Tom Seccull of Queen’s University Belfast.

It is, nevertheless, very difficult to study.

The 300 kilometre-wide (186 mile) space rock is four billion kilometres from Earth, and dark.

“It’s like observing a giant mountain of coal against the pitch-black canvas of the night sky,” said co-author Thomas Puzia of the Pontifical Catholic University of Chile.

Dubbed 2004 EW95, the asteroid is moving, and feint.

“We had to use a pretty advanced data processing technique to get as much out of the data as possible,” said Seccull.