User:Ems57fcva/sandbox/Planet X


 * This article is about the hypothetical planet. For the comic book storyline, see Planet X (comics).

Planet X is a large hypothetical planet orbiting beyond the orbit of Neptune. Its existence was argued for on the basis of apparent discrepancies in the orbits of the gas giants, especially those of Uranus and Neptune.

Although Pluto was discovered as a result of the search for planet X, it is not planet X.

July 29, 2005: The discovery of Kuiper Belt object 2003 UB313, which appears to be larger than Pluto, is announced. See the New discovery section.

The search for Planet X
At the end of the 19th century, many astronomers were speculated about the existence of a planet beyond Neptune. The discovery of Neptune had ocurred because of the calculations of the mathematicians Adams and Le Verrier. Those calculations were based on discrepancies between the calculated and observed orbits of Uranus, Saturn, and Jupiter. However, there still were some slight discrepancies in those orbits after the discovery of Neptune, and also in the orbit of Neptune. These were taken to indicate the existance of yet another planet orbiting beyond Neptune.

Percival Lowell, who is most well known as a proponent for canals on Mars, called this hypothetical planet "Planet X" (X for "unknown", not the Roman numeral "ten", as only eight planets were known at the time). He performed two searches for it, without success, the first ending in 1909, and the second started in 1913 after revising his prediction for where it should be found. This search ended in 1915, after which Lowell published his theoretical results parameters for Planet X. Ironically, at his observatory that year, two faint images of Pluto were recorded, but it was not recognized as a planet at the time. Finally another search was started at the Lowell Observatory in 1928. That search ended with the discovery of Pluto by Clyde Tombaugh in 1930.

Upon its discovery, Pluto was originally thought to be Planet X, but its mass was not sufficient to explain Neptune's orbit, so the search continued. However these apparent discrepancies were resolved when the space probes Pioneer 10, Pioneer 11, and Voyagers 1 and 2 discovered that the masses of the gas giants had been miscalculated. When the correct masses were used to calculate the orbits of the outer planets, the remaining discrepancies vanished. In addition, there have been no discrepancies in the trajectories of the above mention space probes that can be accounted for by the gravitational pull of a large undiscovered object in the solar system.

Results of searches for Planet(s) X
After discovering Pluto, Tombaugh continued to search the ecliptic for other distant planets. He found asteroids, variable stars, and even a comet, but no more planets.

The distant space probes have also acted as planet searchers, since their paths would be affected by any sufficiently close and massive objects. So far, no discrepancies have been found in their trajectories that can be explained by trans-Neptunian planets.

After the distocovery of Pluto, no more trans-Neptunian objects were found until the discovery of (15760) 1992 QB₁ in 1992. Since that time, more and more trans-Neptunian objects have been discovered. The objects are now recognized as mosly belonging to the Kuiper Belt: icy bodies orbiting in the plane of the ecliptic beyond Neptune which are left over from the formation of the solar system. Pluto itself is now recognized as being the largest of the Kuiper Belt objects. This has caused there to be some concern over whether Pluto should be called a planet, but at this time Pluto officially remains a planet.

The Kupier Belt comes to a sudden end at 55 AU. There is speculation that this is caused by the presense of an object with a mass intermediate between those of Mars and Earth beyond 55 AU. So the story of the search for Planet X may not be over yet.

Another object, Sedna, was discovered in 2004 and is the most distant known object in the solar system. It is speculated to be an inner member of the Oort cloud, which is a distant reservoir of comets created when most of the original population of the Kuiper Belt was scattered by the outer planets early in the history of the solar system.

New discovery
On July 29, 2005, the discovery of the Kuiper Belt object 2003 UB313 was announced. 2003 UB313 appears to be bigger than Pluto. It is 97 AU from the Sun in an orbit tilted 44&deg; with respect to the ecliptic. It was discovered by Michael E. Brown (Caltech), Chad Trujillo (Gemini Observatory), and David Rabinowitz (Yale University) using the Gemini North telescope.

See the Sky and Telescope article on 2003 UB313 for more information.

Planet X in Myth
The Sumerian scholar Zecharia Sitchin, in his book The 12th Planet, discusses the planet Nibiru on a long, elliptical orbit, which reaches the inner solar system every 3600 years. This is considered to be pseudoscience by mainstream scientists and historians. See Nibiru (myth).

Planet X in Fiction

 * In Larry Niven's Known Space universe, Persephone is a small gas giant with a single moon, Kobold.
 * In Douglas Adams's novel Mostly Harmless, Planet X is officially called Persephone, but nicknamed Rupert, and is inhabited by the crew of a spaceship who have forgotten almost everything about their mission, except that they are supposed to be "monitoring" something.
 * In the sixth Godzilla film, Monster Zero, aliens known in Japan as X-seijin and in America as Xians hail from Planet X, between Jupiter and Saturn.
 * In Doctor Who, the tenth planet of the solar system is called Mondas, home of the Cybermen. Mondas is/was a twin planet of Earth.
 * In some Looney Tunes cartoons, while in space a there is usually a planet X. The name is either noted by a bland sign sticking out saying PLANET X, or a giant letter X on the planet's surface. Also Planet X in some cartoons is followed by planets named after other letters, such as Planet Q or Planet Z.
 * The computer RPG Ultima II has a Planet X that must be visited to acquire an artifact.
 * The TV series Space: 1999 features the 10th planet in its premiere episode.
 * Although not considered canon, a 1970s publication entitled Star Trek Maps suggests that, in the Star Trek universe, the solar system has a 10th planet called Persephone that orbits at a great distance from the Sun. No canonical film or TV episode has yet supported this, however.