The Nibiru collision is a supposed disastrous encounter between the Earth and a large planetary object (either a collision or a near-miss) which certain groups believe will take place in the early 21st century. Believers in this doomsday event usually refer to this object as Planet X or Nibiru. The idea that a planet-sized object could collide with or pass by Earth in the near future is not supported by any scientific evidence and has been rejected as pseudoscience by astronomers and planetary scientists. Believers in Planet X/Nibiru have often confused it with Nemesis, a hypothetical star first proposed by physicist Richard A. Muller. In 1984, Muller postulated that mass extinctions were not random, but appeared to occur in the fossil record with a loose periodicity that ranged from 2634 million years. He attributed this supposed pattern to a heretofore undetected companion to the Sun, either a brown dwarf, a dim red dwarf or a gas giant planet, lying in an elliptical, 26-million-year orbit. This object, which he named Nemesis, would, once every 26 million years, pass through the Oort cloud, the shell of over a trillion icy objects believed to be the source of long-period comets that orbit at thousands of times Pluto's distance from the Sun. Nemesis's gravity would then disturb the comets' orbits and send them into the inner Solar System, causing the Earth to be bombarded. However, to date no direct evidence of Nemesis has been found. Though the idea of Nemesis appears similar to the Nibiru collision, they are, in fact, very different, as Nemesis, if it existed, would have an orbital period thousands of times longer, and would never come near Earth itself. Still others confuse Nibiru with Eris; a trans-Neptunian object discovered by astronomer Mike Brown in 2005. However, despite having been described as a "tenth planet" in an early NASA press release, Eris (provisional designation: 2003 UB313) is now classified as a dwarf planet. Only slightly larger than Pluto, Eris has a well-determined orbit that never takes it closer than 5.5 billion km from the Earth. Mike Brown believes the confusion results from both the real Eris and the imaginary Nibiru having extremely elliptical orbits. University of Louisiana at Lafayette for an object they believe to be influencing the orbits of comets in the Oort cloud. The name, after the "good sister" of the Greek goddess Nemesis, was chosen to distinguish it from the similar Nemesis hypothesis as, unlike Nemesis, Matese and Whitmire do not believe that their object poses a threat to Earth. However, this object, if it exists, would, like Nemesis, have an orbit hundreds of times longer than that proposed for Nibiru, and never come near the inner Solar System. Some have also associated Nibiru with Comet Elenin, a long-period comet discovered by Russian astronomer Leonid Elenin on December 10, 2010. On 16 October 2011, Elenin will make it's closest approach to the Earth at a distance of 0.2338 AU (34,980,000 km; 21,730,000 mi), which is slightly closer than the planet Venus. Nevertheless, this has led some conspiracy websites to conclude that it is on a collision course, that it is as large as Jupiter or even a brown dwarf, and even that the name of the discoverer, Leonid Elenin, is, in fact, code for ELE, or an Extinction Level Event. Although the sizes of comets are difficult to determine without close observation, Comet Elenin is likely to be less than 10 km in diameter. Elenin himself estimates that the comet nucleus is roughly 34 km in diameter. This would make it millions of times smaller than the supposed Nibiru. Comet hysteria is not uncommon. In 2011, Leonid Elenin ran a simulation on his blog in which he increased the mass of the comet to that of a brown dwarf (0.05 solar masses). He demonstrated that its gravity would have caused noticeable changes in the orbit of Saturn years before its arrival in the inner Solar System. Astronomers point out that such an object so close to Earth would be easily visible to the naked eye (Jupiter and Saturn are both visible to the naked eye, and are dimmer than Nibiru would be at their distances), and would be creating noticeable effects in the orbits of the outer planets. Some counter this by claiming that the object has been hiding behind the Sun for several years, though this would be geometrically impossible. Images of Nibiru near the Sun taken by amateurs are usually the result of lens flares, false images of the Sun created by reflections within the lens. Mike Brown notes that if this object's orbit were as described, it would only have lasted in the Solar System for a million years or so before Jupiter expelled it, and that there is no way another object's magnetic field could have such an effect on Earth. Lieder's assertions that the approach of Nibiru would cause the Earth's rotation to stop or its axis to shift violate the laws of physics. In his rebuttal of Immanuel Velikovsky's Worlds in Collision, which made the same claim that the Earth's rotation could be stopped and then restarted, Carl Sagan noted that, "the energy required to brake the Earth is not enough to melt it, although it would result in a noticeable increase in temperature: The oceans would [be] raised to the boiling point of water ... [Also,] how does the Earth get started up again, rotating at approximately the same rate of spin? The Earth cannot do it by itself, because of the law of the conservation of angular momentum." In a 2009 interview with the Discovery Channel, Mike Brown noted that, while it is not impossible that the Sun has a distant planetary companion, such an object would have to be lying very far from the observed regions of the Solar System to have no gravitational effect on the other planets. A Mars-sized object could lie undetected at 300 AU (10 times the distance of Neptune); a Jupiter-sized object at 30,000 AU. To travel 1000 AU in two years, an object would need to be moving at 2400 km/s faster than the galactic escape velocity. At that speed, any object would be shot out of the Solar System, and then out of the Milky Way galaxy into intergalactic space.  Conspiracy theories Many believers in the imminent approach of Planet X/Nibiru accuse NASA of deliberately covering up visual evidence of its existence. One such accusation involves the IRAS infrared space observatory, launched in 1983. The satellite briefly made headlines due to an "unknown object" that was at first described as "possibly as large as the giant planet Jupiter and possibly so close to Earth that it would be part of this Solar System". This newspaper article has been cited by proponents of the collision idea, beginning with Lieder herself, as evidence for the existence of Nibiru. However, further analysis revealed that of several unidentified objects, nine were distant galaxies and the tenth was "intergalactic cirrus"; none were found to be Solar System bodies. Another accusation frequently made by websites predicting the collision is that the U.S. government built the South Pole Telescope (SPT) to track Nibiru's trajectory, and that the object has been imaged optically. However, the SPT (which is not funded by NASA) is a radio telescope, and cannot take optical images. Its South Pole location was chosen due to the low-humidity environment, and there is no way an approaching object could be seen only from the South Pole. The "picture" of Nibiru posted on YouTube was revealed, in fact, to be a Hubble image of the expanding light echo around the star V838 Mon.  Public reaction The impact of the public fear of the Nibiru collision has been especially felt by professional astronomers. Mike Brown now says that Nibiru is the most common pseudoscientific topic he is asked about. David Morrison, director of SETI, CSI Fellow and Senior Scientist at NASA's Astrobiology Institute at Ames Research Center, says he receives 20 to 25 emails a week about the impending arrival of Nibiru; some frightened, others angry and naming him as part of the conspiracy to keep the truth of the impending apocalypse from the public, and still others asking whether or not they should kill themselves, their children or their pets Half of these emails are from outside the U.S. "Planetary scientists are being driven to distraction by Nibiru," notes science writer Govert Schilling, "And it is not surprising; you devote so much time, energy and creativity to fascinating scientific research, and find yourself on the tracks of the most amazing and interesting things, and all the public at large is concerned about is some crackpot theory about clay tablets, god-astronauts and a planet that doesn't exist." Morrison states that he hopes that the non-arrival of Nibiru could serve as a teaching moment for the public, instructing them on "rational thought and baloney detection", but doubts that will happen. Morrison noted in a lecture recorded on FORA.tv that there was a huge disconnect between the large number of people on the Internet who believed in Nibiru's arrival in 2012 and the majority of scientists who have never heard of it. To date he is the only major NASA scientist to speak out regularly against the Nibiru phenomenon.  Cultural influence A viral marketing campaign for Sony Pictures' 2009 film 2012, directed by Roland Emmerich, which depicts the end of the world in that year, featured a supposed warning from the "Institute for Human Continuity" that listed the arrival of Planet X as one of its doomsday scenarios. Mike Brown attributes a spike in concerned emails and phone calls he received from the public to this site. Lars von Trier's 2011 film Melancholia features a plot in which a planet emerges from behind the Sun onto a collision course with Earth. Announcing his company's purchase of the film, the head of Magnolia Pictures said in a press release, "As the 2012 apocalypse is upon us, it is time to prepare for a cinematic last supper."