There's something weird going on beyond Neptune

Past Neptune, in the outer solar system, astronomers have recently discovered a new mystery object orbiting the sun on a plane nearly perpendicular to the rest of the planets. Adding to the weirdness, the trans-Neptunian object, which has been nicknamed "Niku," is also spinning around the sun backwards, in the opposite direction of the rest of the planets. So far, astronomers have little idea what could cause such abnormal celestial behavior.
They initially thought the other mysterious object beyond Neptune, Planet Nine might have influenced Niku's orbit, but further analysis showed Niku is too close for any possible Planet Nine to have an impact. The team did, however, discover that Niku, which is estimated to be less than 200 kilometers in diameter, is actually a part of a group of objects, all of which are circling the sun backwards on the same 110-degree plane.

https://www.engadget.com/2016/08/10/beyond-neptune-niku-discovery/