Two studies published on arXiv have identified the hypothetical ~10 Earth mass "Planet Nine" as an explanation for the tilt of the solar system:
Two recent studies have shown that the existence of a mysterious, hypothetical Planet Nine could explain why the planets in our Solar System don't fully line up with the Sun. Researchers have been speculating about a ninth planet since January this year, and these latest studies add more weight to the hypothesis that, at some point in time at least, there was an extra planet orbiting our Sun. In fact, if Planet Nine does exist (or did), it would help to explain something that scientists have puzzled over for decades - why the Solar System is tilted.
What does that mean? Well, basically, all of the main eight planets that orbit our Sun do so on the same plane, making the Solar System look like a disc. The problem is that the Sun spins at a different angle, with its axis roughly 6 degrees off from the rest of the planets.
In the past, researchers have attempted to explain this slant by blaming the temporary tug of a passing star, or interactions between the Sun's magnetic field and the disc of dust that formed our planets. But none of these hypotheses have fully accounted for the misalignment. But now the two new studies – [completely independent] from one another in the US and France – show that the existence of Planet Nine could explain the tilt.
Solar Obliquity Induced by Planet Nine
(Score: 0) by Anonymous Coward on Tuesday July 26 2016, @11:04PM
Yes, let's be consistent by using a horrible definition that was not built on its merits, but simply railroaded through for political reasons. Then, to avoid obvious confusion, we will call things that aren't planets "dwarf planets". But dwarf planets are not planets, even though they're called planets, which they're not.
And while you're pretending to play the condescending scientist, what do we call the thousands of "exoplanets" that have been found? They're surely not planets, because by Official Decree, a planet must be in orbit about the Sun. The thousands that we know of, and the un-countable number that are out there, are not planets by definition.