Oumuamua, the interstellar asteroid that fascinated space enthusiasts all over the world when it came flying into the path of our telescopes last October, had a ‘violent past’, according to new research.
The interstellar rock was immediately recognised as unusual when it was spotted by astronomers in Hawaii.
Its discovery marked the first observation of a planetesimal – that is, a small body like an asteroid or comet – born in an entirely different planetary system entering our own.
On top of this, Oumuamua’s long, thin shape was unlike anything scientists had seen in our solar system, and the object appeared to be wrapped in an organic coat that shielded the frozen water inside from the Sun.
So unusual was Oumuamua, in fact, that one group of scientists decided to scan its surface in a hunt for alien technology.
That search proved fruitless, but Dr Wesley Fraser at Queen’s University Belfast and his collaborators have published a series of studies since the discovery of the alien object in which they have attempted to comprehensively unravel its mysteries.
In their latest research, published in the journal Nature Astronomy, they have attempted to build a more accurate profile of Oumuamua, suggesting where it came from, and where it is going.
“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,” said Dr Fraser.
“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.”
By analysing the brightness measurements of the object – and how these changed over time – the scientists realised Oumuamua was not spinning periodically like most solar system bodies, but instead spinning chaotically.
According to the scientists, the object could have been in this state for billions of years already, and likely will continue like this for the foreseeable future.
“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 Fraser.
“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.”
Another mysterious aspect of Oumuamua is it colour. Early reports suggested the object had a dark red colour, but Dr Fraser’s research suggested its surface is actually spotty.
When the long face of the object was facing Earth it was largely red, but the new analysis suggested that the rest of the body was likely neutral coloured – “like dirty snow”.
The scientists think Oumuamua is in all likelihood an asteroid, and not an alien spacecraft. However, there is still much about this interstellar visitor, and objects like it, that remains to be understood.
Researchers have suggested there could be more than 46 million similar interstellar objects crossing the solar system every year.
While most of these objects will be too far away to see with current technology, future telescopes should enable scientists to understand more about interstellar messengers like Oumuamua.