There’s something unusual going on in the faint reaches of the solar system beyond Neptune. Researchers using the Panoramic Survey Telescope and Rapid Response System 1 Survey (Pan-STARRS 1) in Hawaii spotted a trans-Neptunian object they’re nicknaming Niku (inspired by the Chinese word for "rebellious"). New Scientist reports that Niku is 160,000 times fainter than Neptune, and could be less than 130 miles across.

The existence of another trans-Neptunian object isn’t surprising—there are more than 1200 of them—but the way that Niku moves is. In their paper posted on arXiv, scientists describe an object that is moving upward in its orbit. Its orbital plane is tilted 110° compared to the rest of the solar system. And it orbits the Sun backwards, in the opposite direction as Earth and the rest of the planets we know and love.

The New Scientist video below does a good job of visually explaining Niku's oddities:

Because of the way that planetary systems form, all objects within a solar system should spin the same way. Niku is like a Roulette ball that started moving in the opposite direction of the wheel’s spin. At some point, something would have had to knock it off course in order to facilitate that kind of direction change. What that might have been, scientists still aren’t sure, adding to Niku’s enigma status. The only thing we know for sure right now is that a lot of astronomers just got excited to solve a mystery.

[h/t New Scientist]

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