Hey, so, remember that really bizarre cigar-shaped asteroid that flew through our Solar System late last year? It whipped around the Sun and back out into space so fast that astronomers almost missed it, but we now know that it actually came from very far away, and it’s the first interstellar asteroid ever observed by mankind. It was such a strange event, and the asteroid’s shape was so peculiar, that some scientists thought it might actually be an alien probe of some kind. That idea was largely debunked, but the story of the odd space rock just took an unexpected turn: it’s apparently spinning.

The long, narrow rock — called Oumuamua in case you had forgotten — has apparently been tumbling for quite some time, and it began its awkward spin long before it entered our Solar System, but researchers only just noticed its behavior due thanks to observations of the amount of light the object reflects towards Earth. The research was published in Nature Astronomy.

Researchers still aren’t sure where Oumuamua originated, so it’s impossible to say when or how the rock began its odd journey or started flipping around, but they’re going with the theory that it must have been involved in some kind of violent collision. The rock is tumbling, rather than rotating around horizontal axis, and that motion has likely caused great pressure over time.

“At some point or another it’s been in a collision,” Dr Wesley Fraser of Queen’s University explains. “The tumbling actually causes stresses and strains internal to the object, and that slowly but surely squeezes and pulls on the object just like tides on the Earth to remove energy from the spin.”

Ever since it was first spotted, scientists have been trying to come up with some kind of an explanation for why Oumuamua looks the way it does. It’s unlike any space rock we’ve ever seen before, and early assumptions seemed to focus on its long journey through space as one possible reason for its strange shape, slowly growing longer as it flew like an arrow towards our Solar System.

The fact that it’s actually tumbling through space rather than flying like a thrown spear would seem to throw that theory right out the window, but it also suggests that the pressure of its spinning may have gradually stretched it out over time. In any case, it’s easily the most interesting visitor mankind has ever spotted.