Proponents of a Nibiru collision claim that a planet, called Nibiru or Planet X, apparently discovered by the Sumerians, will collide with or pass by Earth in 2012, wreaking havoc and devastation. Note that believers originally predicted this would happen in May 2003 based on claims of channeling from aliens. When this failed to happen, it was switched to December 21st 2012, presumably to tie up with the other disaster scenarios that had started to appear. If this object existed, and would arrive in 2012, it would be visible to the naked eye. You would not even need a telescope! Some have also tried to link this with Eris which is a real dwarf planet similar to Pluto. But Eris orbits way out in the outer solar system; the closest it can come to Earth is about 4 billion miles, which is more than 40 times the distance from the earth to the Sun.