One thing that confused me was that this Planet X system is calculated to be 10x the size of Earth, that is not that big, relatively small compared to Jupiter, and yet it is having this huge impact, why? You have to understand that it has an extremely elliptical orbit, this means that as it comes from the furthest reaches of the solar system it is constantly speeding up as it approaches the sun, so although the mass is not that great, the momentum is huge. The speed of this thing as it rounds the Sun is fantastic.