Hi Zorgon,
Have you read "Dark Star: The Planet X Evidence" by Andy Lloyd. I have never read Sitchen's work, as I have been largely put off by all the negative press about his ideas and theories. However, I recently read Lloyd's book and found it both interesting and informative. You may well have read the book or at least come across his website at
http://www.darkstar1.co.uk/. If not, I recommend a perusal of both.
Anyway, he does not buy into all of Sitchin's stuff, but does treat him respectfully. He speculates tha Planet X is actually one of the moons (or planets?) of a brown dwarf, which as I am sure you know is a kind of failed star, or a star that never came to be. He argues that this is within our solar system, but currently out toward or beyond the kuiper belt. A brown dwarf can apparently be around the size of Jupiter(perhaps a little bigger), though it has a far greater mass than such a planet. It is really half way between a planet and a star, as I understand it (and I am no astronomer). Thus the dark star, according to Lloyd, is a brown dwarf and thus a substellar companion of the Sun.
Lloyd argues that this dark star is currently at aphelion (furthest from the Sun) and in a very elliptical orbit. He believes that the reasons that it is not visible to astronomers, at the current time, are as follows. Firstly, because it is at aphelion and thus too distant to be easily seen. Secondly, because it is somewhere in the direction of Sagittarius, a constellation that can be found in the thickest part of the milkyway as seen from Earth. It is thus indistinguishable from the mass of stars, nebulae, etc. that litter that part of the sky. Thirdly, and finally, a brown dwarf, by its very nature, does not give off much light. The combination of these three, he suggests, is why it has not been identified and seen by astronomers. If it has been spotted, it may have been mistaken for a body outside of our solar system, as its motion through the sky (he suggests a 10,800 year orbit of the Sun) is extremely slow as compared to the orbits of the planets, from Eris and Pluto inward.
He also suggests that the perturbations of Uranus and Neptune can best be understood by the presence of a large Jupiter size body in the outer solar system. Small dwarf planets like Pluto and Eris just do not account for this. Lloyd also suggests that it is not the dark star itself that comes into the known planetary zone when it is as perihelion (closest to Sun) but one of its satelites or moons. He suggests that it is this sattelite or moon that is the famed 'Niburu', which may get as close to the Sun as the orbit of Saturn at certain periods in history/prehistory.
As I am no expert on these things, I have no idea what is and is not possible. However, on the surface, his ideas do seem to have some air of credibility about them. Anyway, I would be interested to know what you think?
If Lloyd is right, then there is certainly no suggestion that either the dark star or one of its moons is going to be entering our planetary zone in or around 2012. I certainly can not beleive any such significant body could be missed if it was actually within the planetary zone of our solar system.
Best Wishes
Truthseeker