Meet Niku, the Weird Object Beyond Neptune That Nobody Can Figure Out

An object beyond the orbit of Neptune is acting oddly, violating the traditional rules of orbit, and scientists can't quite explain it yet. The trans-Neptunian object, or TNO, has been nicknamed Niku, a Chinese word for "rebellious." When you consider the fact that Niku orbits the sun in the opposite direction of almost everything else in the solar system, it's not hard to see where the name came from.

About 124 miles in diameter, Niku has risen above the plane of the solar system. It's still rising, in fact, on an orbital plane that is tilted to everything else. Michele Bannister, an astronomer at Queens University​, summed up Niku's incredibly odd behavior in a tweet:

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Niku is 160,000 times fainter than Neptune​, but it has been observed twenty-two times by astronomers, according to a paper published to arXiv​ detailing the discovery. Authored by the astronomer Ying-Tung Chen of Academia Sinca in Taiwan and an international team of astronomers from Harvard to Hawaii to Germany, the paper describes a sense of utter confusion regarding the behavior of this little object.

Niku orbits on a plane that is tilted 110 degrees​ from the plane of the rest of the solar system. One theory is that a large object's gravity is influencing Niku, causing it to orbit at an angle to everything else as well as backward.​ Various theories, like a hidden Super Earth known as Planet Nine, an unseen dwarf star called Nemesis, or an unknown dwarf planet in the Kuiper Belt are all "problematic​" when trying to explain the orbit of Niku, according analyses​ detailed in the arXiv​ paper. (It was another group of objects with a highly inclined orbit that first led astronomers to propose the possibility of Planet Nine.)

Ultimately, Chen and his fellow astronomers conclude that the "mechanism causing and maintaining this common plane is still unknown​." It seems possible that a collision could have sent Niku spiraling off on its own, or that the TNO was captured from another part of the galaxy when it passed close enough to the sun, but whether either of these could explain the object's behavior is still unclear. The team recommends further study, which, given Bannister's excitement about their discovery, is likely to come soon.​

"It's wonderful that it's so confusing," Bannister told ​New Scientist. "I'm looking forward to seeing what the theoretical analysists do once they get their hands on this one."​

Source: New Scientist