Interstellar traveller in our solar system likely had cosmic collision

12 Feb 2018

Illustration of the asteroid called ‘Oumuamua. Image: Giovanni Cancemi/Shutterstock

The first interstellar asteroid to travel in our solar system, ‘Oumuamua, is truly strange, and now we might have an answer for why that is.

Last November, the discovery of one particular object in the solar system caused quite a stir because it was found to be not from around here.

In fact, the object dubbed ‘Oumuamua – after the Hawaiian word for ‘scout’ – was the first interstellar object to arrive in our solar system, and it came with a peculiar trajectory.

However, new research conducted by a team of international scientists led by Queen’s University Belfast has discovered just how its chaotic path came about.

The team began by simply analysing the brightness measurements of the object, and quickly discovered that the asteroid-turned-comet-turned-asteroid was tumbling chaotically, unlike other objects in the solar system.

In fact, it could have been spinning out of control for billions of years, but trying to find out why proves to be its own challenge.

Another mystery solved

One possibility that the team proposed, however, was that ‘Oumuamua collided with another asteroid before it was thrown into the direction of our solar system.

“Our modelling of this body suggests the tumbling will last for many billions of years to hundreds of billions of years before internal stresses cause it to rotate normally again,” said Dr Wes Fraser of the research team.

“While we don’t know the cause of the tumbling, we predict that it was most likely sent tumbling by an impact with another planetesimal in its system, before it was ejected into interstellar space.”

The team was also able to solve the other mystery plaguing scientists: why does the object’s colour change between measurements?

The answer is that its surface is spotty and when the long asteroid was pointed towards Earth-based telescopes, it was largely red while the rest of the body was grey.

In these first scans, the appearance of red raised the possibility that it contained life in the form of organic, carbon-based molecules.

“We now know that beyond its unusual elongated shape, this space cucumber had origins around another star, has had a violent past and tumbles chaotically because of it,” Fraser added.

“Our results are really helping to paint a more complete picture of this strange interstellar interloper. It is quite unusual compared to most asteroids and comets we see in our own solar system.”

Colm Gorey was a senior journalist with Silicon Republic