Also, the reason that the planets all travel in the same direction around the sun is that the solar nebula was spinning in the first place. The planets had to mirror the direction of the solar nebula's original spin. The Perturber orbits the sun in the opposite direction, which suggests that it did not form in the solar nebula. Instead, It was probably traveling through space when it got a bit too close to the sun's gravity. That gravity slingshoted it around the sun into a long, lonely orbit that takes nearly six million years.
Comets are mountains of ice and rock that orbit the sun.
Long-period comets take many thousands of years to make one orbit. They are believed to originate in the the cold, dark outer reaches of the solar system, far beyond the planets, in a region called the Oort cloud. Some of the comets have been deflected into long, skinny orbits that move them into the inner solar system where we can see them and then back outward into the distant region from whence they came. Murray analyzed 13 of those comets and saw the signs of a single massive object that deflected all of them into their current orbits. If the Perturber is a planet as Murray suggests, it must be more like the planet Jupiter than planet Earth.