Planet Nine: Hidden planet might be causing our solar system to wobble, scientists say

The planet is still hypothetical, but if it is real would explain some of the most confusing parts of our own solar systemThe planet is still hypothetical, but if it is real would explain some of the most confusing parts of our own solar system

This artistic rendering shows the distant view from Planet Nine back towards the sun. The planet is thought to be gaseous, similar to Uranus and Neptune. Hypothetical lightning lights up the night side (Caltech/R. Hurt (IPAC))

A huge planet might be hiding at the edge of our solar system and causing it to wobble, according to scientists.

Planet Nine – a hypothesised but not yet proven planet at the outer end of our neighbourhood – might be responsible for the unusual tilt of the sun, according to a new study.

The huge planet, sitting at such a distance away, might be adding a slight wobble to our own solar system. Scientists have long been confused about why we and the rest of the planets appear to be at a jaunty angle when compared with the sun, and the mysterious planet appears to explain why.

All of the planets of our solar system sit roughly flat with respect to the sun, all orbiting around it just a couple of degrees apart at most. But that plane rotates at a strange, roughly six-degree tilt when compared with the sun – making it appear as if our star has been tilted or is wonky.

Until now, scientists didn’t know why that was happening. “It's such a deep-rooted mystery and so difficult to explain that people just don't talk about it,” said Mike Brown, who helped predict Planet Nine.

But if the mysterious planet does exist does exist, as hypothesised, it could explain the strange behaviour.

“Because Planet Nine is so massive and has an orbit tilted compared to the other planets, the solar system has no choice but to slowly twist out of alignment,” Elizabeth Bailey, a graduate student at Caltech and lead author of a study announcing the discovery, said in a statement.

The huge planet appears to be orbiting about 30 degrees off from the same plane that all of the other planets are on. That means that it influences a huge set of other objects and could so help give the impression that the solar system is crooked.

Planet Nine is hypothesised to orbit around the sun but at a huge distance – around 20 times further from the sun that Neptune is. And the rock itself is massive too, about 10 times the size of the Earth.

“It continues to amaze us; every time we look carefully we continue to find that Planet Nine explains something about the solar system that had long been a mystery,” said Konstantin Batygin, an assistant professor of planetary science who worked with Professor Brown to predict information about planet nine.

But while the work might solve one mystery, of why our solar system sits on such a strange wobble, it opens up another: how Planet Nine got into such a strange orbit in the first place. Scientists have suggested that it might be the result of the planet being thrown into the far solar system by one of our more nearby pants, or that it might have been upset by the gravitational pull of other bodies a long time in the solar system’s past.