What was Planet X about?
There are three distinct planet x. 1. A planet (yet undiscovered) that should exist beyond the orbit of Neptune. In the late 1800s, astronomers thought that there was another planet beyond Neptune, because they thought that Neptune’s orbit was (ever so slightly) different than what is should be. The search for that planet x led to the discovery of Pluto. Since then, we found out that Pluto is much smaller than first thought (it cannot be responsible for any perturbation in Neptune’s orbit), AND we found that the “perturbations” were really uncertainties in the calculations. However, with the recent discoveries of other dwarf planets beyond Pluto, statistical analysis tells us that there is a good probability that we will, one day, find something out there that is the size of a real planet. That is the modern Planet X. If it exists (it is only a statistical probability for now), then it would be on a relatively stable orbit (otherwise, we would have already seen large perturbations in t
