There’s a newly discovered addition to the Solar System ― and it’s behaving rather strangely.

The Solar System is, in a sense, very flat. Nearly everything is moving around the sun along a similar plane and in the same direction. But this new trans-Neptunian object, which measures less than 125 miles in diameter, is different.

According to New Scientist, the unknown is tilted 110 degrees from the rest of the Solar System and moving upward, away from everything else. It’s moving in the opposite direction of everything else, too, like a car on the wrong side of the road.

And it may not be alone.

There appears to be a cluster of objects traveling together along this rebellious path. As a result, scientists have named the new object Niku, which means “rebellious” in Chinese.

I hope everyone has buckled their seatbelts because the outer solar system just got a lot weirder. — Michele Bannister (@astrokiwi) August 8, 2016

Niku was found by Pan-STARRS in Hawaii, a system of telescopes and cameras created to detect near-Earth objects. While it’s not the only object in the Solar System with a retrograde orbit ― there are a handful of others, although NASA says most are comets ― Niku is puzzling scientists, who admit they don’t yet know what’s causing its unusual orbit.

“An unknown mechanism is required to explain the observed clustering,” a research team from the Harvard–Smithsonian Center for Astrophysics wrote in findings published on arXiv.

Popular Mechanics reports that Niku, which is 160,000 times fainter than Neptune, has been spotted 22 times. Various theories, ranging from a hidden planet to an unseen star, are all “problematic” when trying to explain its unusual behavior.

“It suggests that there’s more going on in the outer Solar System than we’re fully aware of,” astrophysicist Matthew Holman, part of the team that discovered Niku, told New Scientist.