Belfast Telegraph

Queens University boffin reveals story behind first alien visitor

By Staff Reporter

A Queen's University academic has uncovered the violent past of the first ever interstellar visitor to our solar system.

The object, which has been named 'Oumuamua, sped across our solar system in October and was originally thought to be a comet.

But it was later revealed to be a cucumber-shaped asteroid.

Since October Dr Wes Fraser, Dr Pedro Lacerda, Dr Michele Bannister and Professor Alan Fitzsimmons, all from Queen's University's School of Mathematics and Physics, have been analysing the brightness measurements of the rock.

They have been working with an international team, including Dr Petr Pravec of the Academy of Sciences of the Czech Republic, Dr Colin Snodgrass from The Open University and Igor Smolic from the University of Belgrade.

The team discovered that 'Oumuamua wasn't spinning periodically like most of the small asteroids we see in our solar system, but instead it was tumbling, or spinning chaotically, and could have been for many billions of years.

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.

Dr Fraser explained: "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.

"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."

Scientists had been puzzled that 'Oumuamua's colour appeared to vary 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.

"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," he said.

The research findings are published in Nature Astronomy.

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