"Angular momentum forces everything to have that one spin direction all the same way," astronomer Michele Bannister from Queens University Belfast in the UK, who wasn't involved in the find, told New Scientist. "It's the same thing with a spinning top, every particle is spinning the same direction."

So for Niku to break with this, scientists think the object must have come into collision with something else, or was pulled off course by another gravitational source. But right now, nobody knows what this other object or group of objects could be.

It's possible that Niku is part of a group of objects all moving with an unusual alignment to the plane of the Solar System.

If such a grouping sounds familiar, that could be because it was this kind of gathering of unusually aligned objects in the Kuiper belt that gave rise to the Planet Nine hypothesis – the suspected (but unconfirmed) massive planet on the fringes of the Solar System that orbits the Sun once every 10,000 to 20,000 years.

Holman and the Niku team examined whether Niku's unusual movements could be attributed to the existence of Planet Nine – or perhaps a dwarf planet in the vicinity – but the minor planet is too close to the centre of the Solar System, so there's still no explanation as yet.

"We don't know the answer," admits Holman.

It's worth pointing out that the team's study has yet to be peer-reviewed, but it's available on arXiv.org while the researchers take feedback prior to publication. Until that time, or until we know more, some are taking the Niku findings with a grain of salt.

"As they say in the paper, what they have right now is a hint," Konstantin Batygin, one of the researchers who suggested the existence of Planet Nine, told New Scientist. "If this hint develops into a complete story that would be fantastic."

[link to www.sciencealert.com]