‘Oumuamua had a violent past and has been tumbling around for billions of years

`Oumuamua had a violent past and has been tumbling around for billions of years
Credit: ESO/M. Kornmesser

The first discovered interstellar visitor to our solar system
has had a violent past, which is causing it to tumble around
chaotically, a Queen’s University Belfast scientist has

‘Oumuamua flew through our solar system in October and was
originally thought to be a comet, then it was later revealed as
a cucumber-shaped asteroid.

Since October, Dr. Wes Fraser, alongside Dr. Pedro Lacerda, Dr.
Michele Bannister, and Professor Alan Fitzsimmons, all from
Queen’s University Belfast’s School of Mathematics and Physics,
have been analysing the brightness measurements of the object.
They have been working with an international team, including
Dr. Petr Pravec from the Academy of Sciences of the Czech
Republic, Dr. Colin Snodgrass from The Open University and Igor
Smolic ́from the University of Belgrade.

Straight away, they discovered that ‘Oumuamua wasn’t spinning
periodically like most of the small asteroids and bodies that
we see in our solar system. Instead, it is tumbling, or
spinning chaotically, and could have been for many billions of

While it is difficult to pinpoint the exact reason for this, it
is thought that ‘Oumuamua impacted with another asteroid before
it was fiercely thrown out of its system and into interstellar

Dr. Fraser explains: “Our modeling 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.

“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 .”

Until now, scientists had been puzzled that ‘Oumuamua’s colour
varied between measurements. However, Dr. Fraser’s research has
now revealed that its surface is spotty and that when the long
face of the cucumber-shaped object was facing telescopes on
Earth it was largely red but the rest of the body was neutral
coloured, like dirty snow.

Dr. Fraser explains: “Most of the surface reflects neutrally
but one of its long faces has a large red region. This argues
for broad compositional variations, which is unusual for such a
small body.”

The research findings, which have been published in Nature
, have helped to build a more accurate profile of

“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. 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,” comments Dr. Fraser.

Since ‘Oumuamua was spotted in October, a team of researchers
at Queen’s University Belfast have been analysing the object in
detail. This is the third paper to be published by their team,
which includes Ph.D. students Meabh Hyland and Thomas Seccull.
Dr. Wes Fraser, Dr. Michele Bannister, Dr. Pedro Lacerda and
Professor Alan Fitzsimmons have been supported by funding from
the Science and Technology Facilities Council for their

Explore further:

Alien object ‘Oumuama was a natural body visiting from another
solar system

More information: Wesley C. Fraser et al. The tumbling
rotational state of 1I/’Oumuamua, Nature Astronomy
(2018). DOI: 10.1038/s41550-018-0398-z