One fear is that a rogue planet that has been dubbed "Nibiru" or "Planet X" is supposedly aimed at Earth. Self-proclaimed Nibiru expert Nancy Lieder, who says she is in contact with the aliens from Zeta Reticuli, first said Nibiru would cause widespread disaster in May 2003, only to change it to Dec. 21, 2012.
There is, however, no evidence that Nibiru is real.
"Nibiru is ridiculous because it doesn't exist — it never existed as anything other than a figment of the imagination by pseudo-scientists who don't seem bothered by a complete lack of evidence," astronomer Don Yeomans, manager of NASA's Near-Earth Object program office at the Jet Propulsion Laboratory in Pasadena, Calif., told SPACE.com.
There is no basis for the claim that it might be lurking behind the sun, as it could not have hidden from observation until now, Yeomans said. If such a planet was headed toward Earth by Dec. 21, 2012, it would already be visible to the naked eye.