First of all, is it Nibiru or is it Planet X? These are not one in the same (mythical) planet. Nibiru is supposedly a rogue planet that will collide with Earth at the end of the year coinciding with the end of the Mayan calendar. This gives rise to the myth that the Mayans knew of the planet Nibiru(where is the proof?)
However, I have heard Planet X otherwise described as an undiscovered planet that orbits the sun exactly in Earth's orbital path but is always located on the opposite side of the sun from us.(in this case how could it ever collide with us?)
But despite all the stuff one hears online, there is no scientific evidence supporting either of these alleged planet's existence.
Nibiru has been linked to NASA by various bloggers, and is also sometimes referred to or confused with Planet X, another supposed world for which there is no evidence. Because of the Nibiru NASA connection that’s been claimed, the space agency put out a statement to say there is no Nibiru or Planet X coming to destroy Earth in 2012.
Here is the true science and history of these supposed rogue planets, with reference to a real object, Comet Elenin, that somehow got mixed up in the whole mess.
Click image for complete story and videos about these supposed death planets at Space.com*
*Space.com is the first place I go, even before NASA.com, for any space related information I may seek. They have the latest, most researched information out there. They are not biased nor opinionated and they give several story related links for your confirmation convenience. :)
I love these guys!