spaceSpace and Physics

An Alien Spacecraft May Have Passed Through Our Solar System Last Year, Claim Scientists


Jonathan O'Callaghan

Senior Staff Writer


An artist's impression of 'Oumuamua. ESO/M/Kornmesser

Slightly more than one year ago, we spotted an object from another star traveling through our Solar System for the first time. There was some debate over whether it was a comet or an asteroid – but could it instead have been an alien spacecraft equipped with a solar sail?

Well, no. But still, two scientists have looked into the plausibility of such a scenario anyway, noting some peculiarities in the object – dubbed ‘Oumuamua – that could lend credence to such an explanation. The story was first picked up by Matt Williams at Universe Today.


The study, which is available on the pre-print server arXiv and has been submitted to the Astrophysical Journal Letters, was conducted by Shmuel Bialy and Avi Loeb from the Harvard Smithsonian Center for Astrophysics in Cambridge, Massachusetts.

‘Oumuamua was odd in that, as it swung past the Sun, it appeared to get a strange speed boost. Scientists have put this down to an outgassing event – with the object firing material from its surface like a jet as it was heated by the Sun.

Bialy and Loeb, however, argue against such an idea. They say the lack of additional rotation in the 400-meter-long object (1,300 feet) caused by the event makes it unlikely an outgassing event was the cause of the change in motion. Instead, they say the acceleration “may be explained by solar radiation pressure”.

“If radiation pressure is the accelerating force, then ‘Oumuamua represents a new class of thin interstellar material, either produced naturally, through a yet unknown process in the ISM [interstellar medium] or in proto-planetary disks, or of an artificial origin,” they write.


“Considering an artificial origin, one possibility is that ‘Oumuamua is a lightsail, floating in interstellar space as a debris from an advanced technological equipment.”

Such ideas have been considered on Earth for our own journeys to distant stars. The Breakthrough Starshot project, for example, proposed using a lightsail to reach our nearest star system – Alpha Centauri – within a generation.

If this were true for ‘Oumumamua, the duo are unsure whether the object was accidentally sent towards us – “equipment that is not operational any more” – or an operational probe “sent intentionally to Earth vicinity by an alien civilization.” They say it could have come from any star within 16,000 light-years.

Unfortunately, ‘Oumuamua is now too far from Earth to study it further, let alone visit it, and it will never return again. So we'll never be able to test this theory, however ridiculous it might be.


"The key issue with this theory is that it cannot possibly be tested," Dr René Heller from the Max Planck Institute for Solar System Research told IFLScience. "It is also an extraordinary claim without extraordinary evidence."


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