A new astronomy paper suggests that the strange object named Oumuamua that passed through our solar system a couple of years ago was probably a thin disc of planetary matter (opens new window), and not a piece of alien technology.

Scientists have been genuinely baffled by what they saw when Oumuamua (opens new window) passed through our solar system, in a trajectory and speed that didn’t match those of an object which originated from our solar system. It was also shiny, and accelerated as it went past, which was a little odd given that there was no visible tail from outgassing.

Although most scientists accept that the most likely answer to this riddle is that the object is natural but unknown, Avi Loeb from Harvard insists that it’s aliens. In fact he seems impervious to alternative answers, even though they’re more plausible than his alien solar sail idea. This may be because he recently published a book called "Extraterrestrial: The First Sign of Intelligent Life Beyond Earth", and accepting a natural origin makes the thesis of his book wrong.

This new paper suggests that the gas which propelled Oumuamua was nitrogen, and this would explain why no comet-like tail was visible.

When I first started reading about how weird this object was, and how it defied any kind of rational explanation, I was excited - especially when respected scientists started talking about a possible intelligent origin. Of course, this is a major pitfall that skeptics can fall in to - and I’m certainly not impervious to this kind of trap. We tend to let our guard down when the thing we’re being asked to believe is something we want to be true. But we have to try our hardest to be just as rigorous and critical of these exciting ideas as the ones we’re not invested in.

Although Oumuamua was the first of these kinds of objects we have seen, it’s not the only one. In 2019 comet 2I/Borisov (opens new window) was spotted in another strange orbit, suggesting that it too came from somewhere outside of the solar system. As our technology for monitoring the sky improves, expect to hear more of these stories as we learn more about what’s out there - and remember, if you read an article talking about how a new space object is aliens, it’s probably not aliens.