New York: Planet Nine -- the undiscovered one at the edge of our solar system -- appears to be responsible for the unusual tilt of the Sun, say researchers.
Planet Nine was predicted by Konstantin Batygin and Mike Brown from California Institute of Technology's (Caltech) in January this year.
The large and distant planet may be adding a wobble to the solar system, giving the appearance that the sun is tilted slightly.
"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," said Elizabeth Bailey, graduate student at Caltech and lead author of a study announcing the discovery.
All of the planets orbit in a flat plane with respect to the sun, roughly within a couple degrees of each other.
That plane, however, rotates at a six-degree tilt with respect to the sun--giving the appearance that the sun itself is cocked off at an angle.
Brown and Batygin's discovery of evidence that the sun is orbited by an as-yet-unseen planet - that is about 10 times the size of Earth with an orbit that is about 20 times farther from the sun on average than Neptune's - changes the physics.
Planet Nine, based on their calculations, appears to orbit at about 30 degrees off from the other planets' orbital plane, influencing the orbit of a large population of objects in the Kuiper Belt.
"Every time we look carefully, we continue to find that Planet Nine explains something about the solar system that had long been a mystery," added Batygin, assistant professor of planetary science.
How did Planet Nine achieve its unusual orbit?
Though that remains to be determined, Batygin suggests that the planet may have been ejected from the neighbourhood of the gas giants by Jupiter, or perhaps may have been influenced by the gravitational pull of other stellar bodies in the solar system's extreme past.
The findings have been accepted for publication in the Astrophysical Journal.