Nibiru was the name given (by the ancient Sumerians) to what has been 'renamed' in the current day to "Planet X".. Prior to Aug. 12-25 of 2006 It was supposed to be the "un-official" 9th planet in our solar system (or the 12th Planet by book name according to the late Zechariah Sitchin). But after said date, where the International Astronomical Union (IAU) General Assembly was held in Prague, which determined that our solar system now has 12 officially recorded planets. Then that makes Nibiru our "un-official" 13th planet. Either way, It's either part of us or it's not, but after 30+ years of various study including all of Sitchin's books plus countless others on the subject.. I personally choose to believe it is and I also believe one day within my lifetime, everyone on Earth will become aware of it. ((Google It.. there are various web sites many of which are of a conspiracy nature, but none-the-less it is known of by several people))