Joint-shaped space projectile 'Oumuamua is a comet

Ouamuamua in space.
Ouamuamua in space. Photo credit: ESO

A strangely shaped interstellar object spotted last year has been confirmed as a comet, scientists rejecting speculation it was a broken-down space ship.

'Oumuamua was considered by some to be the right shape for a spaceship, and many believe it looked like a cigar or even a joint.

There were suggestions it was even made of metal instead of rock, but astronomers at the European Space Agency have confirmed it is just a comet.

It all comes down to the way the 'Oumuamua has been moving around in space. The Italian scientists that followed 'Oumuamua said its movement couldn't be explained entirely by the gravitational effects of the sun, so it must have had another form of propulsion - which turned out to be gas, just like a comet.

Other explanations for the non-gravitational motion, such as pressure from solar radiation or magnetic interaction with solar wind, were ruled out.

It took so long to realise it was a comet because it didn't have a "coma of atmosphere and dust", like they usually do.

So there you have it - it's not a spaceship, an asteroid or some kind of mystery new material. It's just a comet.

Scientists still have no idea where it came from, however, except that it wasn't from our own solar system.

Their research was published in journal Springer Nature.

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