In astronomy, Planet X is a large hypothetical planet beyond Neptune. It was postulated to explain apparent discrepancies in the orbits of the gas giants, especially those of Uranus and Neptune. Those discrepancies were mostly resolved by measurements made in the 1980s.^[1] ZetaTalk is a website that was started in 1995 by self-proclaimed contactee Nancy Lieder, who claims to channel messages from extra-terrestrials who refer to themselves as the Zetas (from the Zeta Reticuli star system; see Betty and Barney Hill) through an implant in her brain. ... Planet X was a hypothetical planet believed to be beyond Pluto. ... For other uses, see Astronomy (disambiguation). ... An artists rendering of a hypothetical exoplanet. ... For other uses, see Neptune (disambiguation). ... Two bodies with a slight difference in mass orbiting around a common barycenter. ... This article does not cite any references or sources. ... For other uses, see Uranus (disambiguation). ... For other uses, see Neptune (disambiguation). ...

The "X" in the name represents an unknown and is pronounced as the letter, as opposed to the Roman numeral for ten. At the time of its conception there were eight known planets in the solar system; its existence, first as a ninth planet, and then from 1930 until its demise as a tenth. Although Pluto was discovered as a result of the search for Planet X, it is not considered Planet X. Neither is Eris, even though it was at one point considered for reclassification as a planet under a proposal outlined by the International Astronomical Union (see 2006 redefinition of planet). The system of Roman numerals is a numeral system originating in ancient Rome, and was adapted from Etruscan numerals. ... This article is about the astronomical term. ... This article is about the Solar System. ... A ninth planet would, according to the currently accepted definition of planet, be a hypothetical planet in the solar system beyond Neptune. ... This article does not cite its references or sources. ... For other uses, see Pluto (disambiguation). ... Absolute magnitude: −1. ... IAU redirects here. ... The final definition left the solar system with eight planets, pictured above (not to scale) Displays the remaining eight planets with the celestial bodies that have now been designated as dwarf planets. ...

In popular culture, "Planet X" has become a stand-in term for an undiscovered planet in the solar system. This article is about the Solar System. ...

Origin of the discrepancy

See also: Discovery of Neptune

At the beginning of the 20th century, many astronomers speculated about the existence of a planet beyond Neptune. The discovery of Neptune resulted from calculations of the mathematicians John Couch Adams and Urbain Le Verrier to explain discrepancies between the calculated and observed orbits of Uranus, Saturn, and Jupiter. Neptune The discovery of the planet Neptune on September 23, 1846 was a dramatic incident in the history of astronomy that also led to a tense international dispute over priority. ... Atmospheric characteristics Surface pressure ≫100 MPa Hydrogen - H2 80% ±3. ... Leonhard Euler, considered one of the greatest mathematicians of all time A mathematician is a person whose primary area of study and research is the field of mathematics. ... John Couch Adams (June 5, 1819 – January 21, 1892), was a British mathematician and astronomer. ... Urbain Le Verrier. ... For other uses, see Uranus (disambiguation). ... Atmospheric characteristics Atmospheric pressure 140 kPa Hydrogen >93% Helium >5% Methane 0. ... Atmospheric characteristics Atmospheric pressure 70 kPa Hydrogen ~86% Helium ~14% Methane 0. ...

After the discovery of Neptune, however there still were some slight discrepancies in those orbits, and also in the orbit of Neptune itself. These were taken to indicate the existence of yet another planet orbiting beyond Neptune.

Percival Lowell, who is most well known for his claims of having observed canals on Mars, called this hypothetical planet "Planet X". He performed two searches for it without success, the first ending in 1909, and after revising his prediction for where it should be found, the second from 1913 to 1915, after which Lowell published his mathematical hypothesis of the parameters for Planet X. Ironically, at his observatory that year, two faint images of Pluto were recorded, but were not recognized at the time.^[2] Percival Lowell (March 13, 1855 – November 12, 1916) was an author, mathematician, and esteemed astronomer who fueled speculation that there were canals on Mars, founded the Lowell Observatory in Flagstaff, Arizona, and formed the beginning of the work and theories that led to the discovery of Pluto 14 years after... For a time in the late 19th and early 20th centuries, it was believed that there were canals on Mars. ... This article is about the astronomical term. ...

Discovery of Pluto

Lowell died in 1916, but in 1928 the Lowell Observatory began another search, which ended with the discovery of Pluto by Clyde Tombaugh in 1930. Lowell Observatory Percival observing Mars from the Clark telescope at the Lowell Observatory. ... An image of Clyde Tombaugh Clyde William Tombaugh (February 4, 1906 – January 17, 1997) was an American astronomer who discovered the dwarf planet Pluto 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. For other uses, see Pluto (disambiguation). ...

Further searches for Planet(s) X

See also: Hypothetical trans-Neptunian planets

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 plane of the ecliptic is well seen in this picture from the 1994 lunar prospecting Clementine spacecraft. ... For other uses, see Asteroid (disambiguation). ... This article or section contains a plot summary that is overly long or excessively detailed. ... Comet Hale-Bopp Comet West For other uses, see Comet (disambiguation). ...

In the 1980s and 1990s, astronomer Robert Sutton Harrington of the US Naval Observatory, who had first calculated that Pluto was too small to have perturbed the orbits of Uranus and Neptune, led a search to determine the real cause of the planets' apparently irregular orbits.^[3] He calculated that any Planet X would be at roughly three times the distance from the sun of Neptune's orbit, highly elliptical, and far below the ecliptic (the planet's orbit would be at roughly a 90-degree angle from the orbital plane of the other known planets).^[4] This hypothesis was met with a mixed reception. Noted Planet X skeptic Brian Marsden of Harvard University's Minor Planet Center has pointed out that these discrepancies are a hundred times smaller than those noticed by Adams and Le Verrier, and could easily be due to observational error.^[3] Robert Sutton Harrington (October 21, 1942 – January 23, 1993) was an American astronomer who worked at US Naval Observatory. ... Aerial view of USNO. The United States Naval Observatory (USNO) is one of the oldest scientific agencies in the United States. ... In mathematics, an ellipse (from the Greek for absence) is a curve where the sum of the distances from any point on the curve to two fixed points is constant. ... The plane of the ecliptic is well seen in this picture from the 1994 lunar prospecting Clementine spacecraft. ... Brian G. Marsden is an astronomer, the longtime director of the Minor Planet Center. ... The Minor Planet Center operates at the Smithsonian Astrophysical Observatory (SAO), which is part of the Center for Astrophysics (CfA) along with the Harvard College Observatory (HCO). ...

In 1972, Joseph Brady of the Lawrence Livermore National Laboratory studied irregularities in the motion of Halley's Comet. Brady claimed that they could have been caused by a Jupiter-sized planet beyond Neptune that orbited the Sun backward. However, both Marsden and Planet X proponent P. Kenneth Seidelmann attacked the hypothesis, showing that Halley's Comet jetted randomly and irregularly, causing changes to its own orbital trajectory, and that such a massive object as Brady's Planet X would have severely affected the orbits of the outer planets.^[3] Aerial view of the lab and surrounding area, facing NW. The Lawrence Livermore National Laboratory (LLNL) in Livermore, California is a United States Department of Energy (DOE) national laboratory, managed and operated by Lawrence Livermore National Security, LLC (LLNS), a limited liability consortium comprised of Bechtel National, the University of... This article is about the comet. ...

While its mission did not involve a search for "Planet X", the IRAS space observatory made headlines briefly in 1983 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."^[5][6] However, further analysis revealed that of several unidentified objects, nine were distant galaxies and the tenth was "intergalactic cirrus".^[7] None were found to be Solar System bodies.^[7] The Infrared Astronomical Satellite (IRAS) was a space-based observatory that performed a survey of the entire sky at infrared wavelengths. ... For other uses, see Jupiter (disambiguation). ... This article is about Earth as a planet. ... This article is about the Solar System. ... Infrared Cirrus are filamentary structures seen in infrared light. ...

After Pluto and Charon (discovered in 1978), no more trans-Neptunian objects were found until the discovery of (15760) 1992 QB₁ in 1992. Since that time, hundreds of trans-Neptunian objects have been discovered. The objects are now recognized as mostly 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 a member of the Kuiper Belt, and the second largest dwarf planet. Pluto lost its status as a planet in 2006 because it failed to meet the new IAU definition of a planet, which would require it to have cleared the neighbourhood around its orbit. Charon (shair-É™n or kair-É™n (key), IPA , Greek Χάρων), discovered in 1978, is, depending on the definition employed, either the largest moon of Pluto or one member of a double dwarf planet with Pluto being the other member. ... A trans-Neptunian object (TNO) is any object in the solar system that orbits the sun at a greater distance on average than Neptune. ... (15760) 1992 QB1 (also written (15760) 1992 QB1) was the first trans-Neptunian object to be discovered after Pluto and Charon. ... The Kuiper belt, derived from data from the Minor Planet Center. ... Artists impression of Pluto (background) and Charon (foreground). ... The final definition left the solar system with eight planets, pictured above (not to scale) Displays the remaining eight planets with the celestial bodies that have now been designated as dwarf planets. ...

Planet X disproved

Harrington died in 1993, having never found Planet X.^[3] That same year, Myles Standish used data from Voyager 2's 1989 flyby of Neptune, which had revised the planet's total mass downward by 0.5 percent, to recalculate its gravitational effect on Uranus.^[8] When the newly determined mass was used in the Jet Propulsion Laboratory Developmental Ephemeris (JPL DE), the supposed discrepancies in its orbit vanished.^[1] Trajectory Voyager 2 is an unmanned interplanetary spacecraft, launched on August 20, 1977. ... For other uses, see Neptune (disambiguation). ... The Jet Propulsion Laboratory Developmental Ephemeris (JPL DE) is a product of the Jet Propulsion Laboratory in Pasadena, California. ...

Also, to date there are no discrepancies in the trajectories of any space probes (Pioneer 10, Pioneer 11, Voyager 1 and Voyager 2) that can be attributed to the gravitational pull of a large undiscovered object in the outer solar system.^[9] Pioneer 10 was the first spacecraft to travel through the asteroid belt, and was the first spacecraft to make direct observations of Jupiter. ... Position of Pioneer 10 and 11 Pioneer 11 was the second mission to investigate Jupiter and the outer solar system and the first to explore the planet Saturn and its main rings. ... For the album by The Verve, see Voyager 1 (album). ... Trajectory Voyager 2 is an unmanned interplanetary spacecraft, launched on August 20, 1977. ...

Planet X revived

See also: The "Kuiper cliff"

The search for Planet X may not be over yet. The Kuiper Belt terminates suddenly at a distance of 55 AU from the Sun, and there is some speculation this sudden dropoff may be caused by the presence of an object with a mass between that of Mars and Earth located beyond 55 AU. Patryk Lykawka, astronomer at Kobe University, Japan, claims that we will discern this object's existence or lack thereof by 2013.^[10] Lykawka's computer simulations suggest that a body roughly the size of Earth, ejected outward by Neptune early in the Solar System's formation and currently set in elongated orbit between 80 and 170 AU from the Sun, could explain not only the Kuiper cliff but also the peculiar "detached" TNOs such as 90377 Sedna. While some astronomers have cautiously supported Lykawka's claims, others have dismissed them as contrived.^[10] The Kuiper belt, derived from data from the Minor Planet Center. ... The Kuiper belt, derived from data from the Minor Planet Center. ... Kobe University in Japan (神戸大学 Kobe Daigaku, abbreviated to 神大 Shindai) is one of the top-rating national universities. ... you are abunch of bull | bgcolour=#FFFFC0 | name=90377 Sedna | image= | caption= Sedna is located in the center of the green circle | discovery=yes | discoverer=M. Brown, C. Trujillo, D. Rabinowitz | discovered=November 14, 2003 | mp_name=90377 Sedna | alt_names= | mp_category=Trans-Neptunian object | epoch=September 26, 1990 (JD 2448160. ...

An alternative theory, proposed in 1999 by John Murray of the Open University and John Matese, Patrick Whitman and Daniel Whitmire of the University of Louisiana at Lafayette, has long period comets originating from specific regions of the sky, rather than coming from random directions as proposed by Oort. This would result from comets being disturbed by an unseen object at least as large as Jupiter, and possibly a brown dwarf.^[11] Affiliations Alliance of Non-Aligned Universities, Association of Commonwealth Universities, European Association of Distance Teaching Universities, Middle States Association of Colleges and Schools Website http://www. ... The University of Louisiana at Lafayette, or UL Lafayette,[1] is a coeducational public research university located in Lafayette, Louisiana, in the heart of Acadiana. ... Jan Hendrik Oort (April 28, 1900 – November 5, 1992) was an internationally famous Dutch astronomer. ... For other uses, see Jupiter (disambiguation). ... This brown dwarf (smaller object) orbits the star Gliese 229, which is located in the constellation Lepus about 19 light years from Earth. ...

See also

• Planet X in popular culture
• Nemesis (star)
• Vulcan (hypothetical planet)
• Oort cloud

Outer planets in fiction are hypothetical or fictional planets on the edge of the Solar System, beyond the orbit of Neptune, which serve as settings in science fiction stories. ... Nemesis is a hypothetical red dwarf star or brown dwarf, orbiting the Sun at a distance of about 50,000 to 100,000 AU, somewhat beyond the Oort cloud. ... Vulcan was the name given to a small planet proposed to exist in an orbit between Mercury and the Sun in a 19th-century hypothesis. ... Artists rendering of the Oort cloud and the Kuiper Belt. ...

External links

• SEDS on Planet X
• Planet X: No Dynamical Evidence in the Optical Observations - 1993 paper by E. Myles Standish, Jr. of the Jet Propulsion Laboratory, on the absence of orbital perturbation, when corrected planetary mass is used

For the singer/songwriter, see Jon Peter Lewis. ...

References

1. ^ ^{a b} The Neptune File: A Story of Astronomical Rivalry and the Pioneers of Planet Hunting, by Tom Standage, pg. 188
2. ^ Planets Beyond: Discovering the Outer Solar System, by Mark Littman, 1990, pg. 70
3. ^ ^{a b c d} Ken Croswell (1997). Planet Quest: The Epic Discovery of Alien Solar Systems. The Free Press, 56-71. 
4. ^ P. K. Seidelmann and R. S. Harrington (1987). Planet X — The current status. U. S. Naval Observatory. Retrieved on 2007-11-04.
5. ^ Thomas O'Toole. "Mystery Heavenly Body Discovered", Washington Post, 30 December 1983, p. A1. Retrieved on 2008-01-28. 
6. ^ Thomas O'Toole. "Mystery Heavenly Body Discovered", Washington Post, 30 December 1983, p. A1. Retrieved on 2008-01-28. 
7. ^ ^{a b} Thomas J. Chester. No Tenth Planet Yet From IRAS. Thomas J. Chester (CalTech). Retrieved on 2008-01-28.
8. ^ Ken Croswell (1993). Hopes Fade in hunt for Planet X. Retrieved on 2007-11-04.
9. ^ Littmann, pg. 204
10. ^ ^{a b} Govert Schilling (2008). The mystery of Planet X. New Scientist. Retrieved on 2008-02-08.
11. ^ SETH BORENSTEIN (1999). A 10th planet may be out there or new object could be the sun's long-lost twin, astronomers say. Huston Chronicle. Retrieved on 2007-04-01.

• P. K. Seidelmann, R. S. Harrington (1987). "Planet X - The current status". Journa Celestial Mechanics and Dynamical Astronomy 43 (1-4): 55-68. doi:10.1007/BF01234554.
• D. P. Whitmire, J. J. Matese (1985). "Periodic comet showers and planet X". Nature 313: 36 - 38. doi:10.1038/313036a0.
• G. D. Quinlan (1985). "Planet X: a myth exposed". Nature 363: 18 - 19. doi:10.1038/363018b0.
• xfacts.com