I’m here to report that no aliens are coming. At least, not this time.
Scientists have been puzzling over the cigar-shaped comet, dubbed 'Oumuamua after the Hawaiian word for “messenger,” since it was first spotted swooping past the planets at an odd angle. Its speed was so blistering and trajectory so strange that scientists concluded it had to be a visitor from another star. Subsequent observations by dozens of telescopes in every wavelength of the electromagnetic spectrum suggested it was an inert (if extraordinary) space rock — dense, dustless, and reddened by irradiation from cosmic rays.
Just to be on the safe side, astronomers at the Green Bank Telescope in West Virginia specifically listened for signals from any electronic device that might be attached to the object. They didn’t hear a peep.
But then a preprint of a research paper to be published in the Astrophysical Journal appeared online this week, posing an “exotic scenario” in which the 'Oumuamua was a solar-powered probe built by an alien civilization.
There’s no evidence to support this idea. Indeed, the majority of the study is devoted to examining how radiation pressure from the sun might push on a natural object and contribute to 'Oumuamua’s unexplained acceleration. This phenomenon is the basis for a proposed method of spacecraft propulsion called light sails, which I guess is how we get from “whoa, weird rock” to “it might be aliens!” The study authors justify their speculation by arguing that the probability of an ordinary comet intercepting our solar system after being ejected by its home star is very small.
As astrophysicist Katie Mack pointed out on Twitter, coming up with far-out explanations for slightly strange phenomena is one of astronomers' favorite parlor games. (Remember the alien megastructure that turned out to be a star swathed in dust?)
That doesn’t mean you need to stock up on canned goods and tin foil hats every time a weird theory gets published.
“Until every other possibility has been exhausted dozen times over, even the authors probably don’t believe it,” Mack said.
Other astronomers were not so forgiving of their colleagues' speculation.
Since ‘Oumuamua has already sped far from our solar system, out of reach of all telescopes, scientists are stuck with the data they have. Luckily, there’s reams of it — and scores of more likely explanations for the comet’s behavior have not been exhausted.
So, go ahead and cast your vote as if this is the only world we have, and no one else is out there to save us from ourselves.