An artist's rendering of a hypothetical exoplanet.

A hypothetical planet is a planet whose existence is not known, but has been inferred from observational scientific evidence. Over the years a number of hypothetical planets have been proposed, and many have been disproved. However, even today there is scientific speculation about the possibility of planets yet unknown that may exist beyond the range of our current knowledge. Image File history File linksMetadata Size of this preview: 450 × 600 pixelsFull resolution (960 × 1280 pixel, file size: 524 KB, MIME type: image/jpeg) File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... Image File history File linksMetadata Size of this preview: 450 × 600 pixelsFull resolution (960 × 1280 pixel, file size: 524 KB, MIME type: image/jpeg) File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... The eight planets and three dwarf planets of the Solar System. ...

Within our solar system

Our solar system is by no means fully mapped and charted. Much of its territory is still unknown, and many astronomers have hypothesized from indirect observation that other substantial objects could still exist undetected in its farthest reaches. Major features of the Solar System (not to scale; from left to right): Pluto, Neptune, Uranus, Saturn, Jupiter, the asteroid belt, the Sun, Mercury, Venus, Earth and its Moon, and Mars. ...

Vulcan/Vulcanoids

Main articles: Vulcan (hypothetical planet) and Vulcanoid asteroid

In the 19th century, the astronomer Urbain Le Verrier, credited with the discovery of Neptune, attempted to locate a hypothetical planet within the orbit of Mercury that he believed was causing perturbations in its orbit. This planet, which he named Vulcan after the Roman god of the forge due to its closeness to the Sun, was never observed, and Einstein's general relativity theory subsequently resolved the issue of Mercury's orbit.^[1] 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. ... Vulcanoids are hypothetical asteroids that may orbit in a dynamically stable zone between 0. ... Urbain Le Verrier. ... Atmospheric characteristics Surface pressure ≫100 MPa Hydrogen - H2 80% ±3. ... This article is about the planet. ... 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. ... The Sun (Latin: Sol) is the star at the center of the Solar System. ... “Einstein” redirects here. ... General relativity (GR) (aka general theory of relativity (GTR)) is the geometrical theory of gravitation published by Albert Einstein in 1915/16. ...

However, a gravitationally stable region does exist between Mercury and the Sun, and some astronomers, notably Alan Stern, contend that a field of small minor planets, the Vulcanoids, should exist within it. However repeated observations of the region have yet to yield any results, and the Vulcanoids, if they exist, must be rather small and few in number.^[2] Some conclude that the existence of the Vulcanoids is impossible, as any minor planet within the orbit of Mercury would eventually be destabilised by the Yarkovsky effect; motion by the force of its own heat.^[3] This page may meet Wikipedias criteria for speedy deletion. ... Vulcanoids are hypothetical asteroids that may orbit in a dynamically stable zone between 0. ... In physics, the Yarkovsky effect is a force felt by a body caused by the momentum carried away by the thermal photons that it emits. ...

Planet X

Main article: Planet X

See also: Ninth planet and Tenth planet

In the early 20th century, astronomer Percival Lowell's observation of apparent irregularities in the orbits of Uranus and Neptune led him to conclude that a distant planet, which he called Planet X, must lie beyond them. The Lowell Observatory's long search for this planet ultimately led to the discovery of Pluto. However, Pluto's mass was found to be too small to disturb the other planets' orbits significantly, and subsequent measurements by the Voyager 2 spacecraft showed that earlier calculations of Neptune's mass had been in error, leading to the irregularities observed.^[4] Today, few scientists accept Lowell's theory; however, a number of recent observations have reopened the debate on the existence of a "Planet X", even if it would bear little resemblance to that envisioned by Lowell. Planet X is a large hypothetical planet with an orbit beyond that of Neptune. ... 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. ... 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... Adjectives: Uranian Atmosphere Surface pressure: 120 kPa (at the cloud level) Composition: 83% Hydrogen 15% Helium 1. ... Adjectives: Neptunian Atmosphere Surface pressure: ≫ 100 kPa (cloud level) Composition: 80% ± 3. ... Planet X is a large hypothetical planet with an orbit beyond that of Neptune. ... Adjectives: Plutonian Atmosphere Surface pressure: 0. ... Trajectory Voyager 2 is an unmanned interplanetary spacecraft, launched on August 20, 1977. ...

• The Kuiper belt has a very sharply defined edge. At around 49 AU, a sharp dropoff occurs in the number of objects observed. This dropoff is known as the "Kuiper Cliff", and as yet its cause is unknown. Some speculate that something must exist beyond the belt large enough to sweep up the remaining debris, perhaps as large as Earth or Mars. This view is still controversial, however.^[5]

• Physicist Richard A. Muller has hypothesised that the Sun may be part of a binary star system, with a distant companion named Nemesis. Nemesis was proposed to explain some timing regularities of the great extinctions of life on Earth. The hypothesis says that Nemesis creates periodical perturbations in the Oort cloud of comets surrounding the solar system, causing a "comet shower". Some of them hit Earth, causing destruction of life. This hypothesis is no longer taken seriously by most scientists, mostly because infrared surveys failed to spot any such object, which should have been very conspicuous at those wavelengths.^[6]

• Dr. John Murray of the Open University and John Matese of the University of Louisiana at Lafayette believe that the motions of long-term comets in the sky suggest the existence of a large, distant planet, or, more likely, a small substellar companion such as a Brown dwarf, in the deep solar system. This hypothetical substellar object is not Nemesis, since its existence is inferred from a different set of data; however there is the possibility that both sets of data could be true for the same object.^[7]

The Kuiper belt, derived from data from the Minor Planet Center. ... Richard Muller Richard A. Muller (January 6, 1944 -) of San Francisco, California, USA, is a physicist who works at the University of California, Berkeley and Lawrence Berkeley National Laboratory. ... Artists impression of a binary system consisting of a black hole, with an accretion disc around it, and a main sequence star. ... 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. ... This image is an artists rendering of the Oort cloud and the Kuiper Belt. ... Image of two girls in mid-infrared (thermal) light (false-color) Infrared (IR) radiation is electromagnetic radiation of a wavelength longer than that of visible light, but shorter than that of radio waves. ... 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. ... This brown dwarf (smaller object) orbits the star Gliese 229, which is located in the constellation Lepus about 19 light years from Earth. ...

Theia

Main article: Giant impact hypothesis

A onetime Trojan to the Earth that, once its size grew to roughly that of Mars, became unstable in its orbit and collided with the Earth, transforming its crust and upper mantle into a magma ocean, and ejecting massive amounts of light material into orbit, which eventually coalesced into the Moon. This theory is known as the giant impact hypothesis.^[8] The Big Splash. ... Image of the Trojan asteroids in front of and behind Jupiter along its orbital path. ... Adjectives: Martian Atmosphere Surface pressure: 0. ... Apparent magnitude: up to -12. ... The Big Splash. ...

Planets between Mars and Jupiter

Main article: Fifth planet (hypothetical)

To meet Wikipedias quality standards, this article may require cleanup. ...

Phaeton

Main article: Phaeton (hypothetical planet)

A planet situated between the orbits of Mars and Jupiter whose destruction supposedly led to the formation of asteroids and meteorites. One of the first who believed that asteroids are the result of an exploded planet was German astronomer Wilhelm Olbers (1758–1840). The name "Phaeton" for this planet was chosen by the Russian scientist, E. L. Krinov. Nowadays this hypothesis is disregarded by the main scientific community.^{[citation needed]} It has been suggested that this article or section be merged with Fifth planet (hypothetical). ... Adjectives: Martian Atmosphere Surface pressure: 0. ... Adjectives: Jovian Atmosphere Surface pressure: 20–200 kPa[4] (cloud layer) Composition: ~86% Molecular hydrogen ~13% Helium 0. ... Categories: Astronomers stubs | 1758 births | 1840 deaths | German astronomers | German physicists | Lists of asteroids ... Yevgeny Leonidovich Krinov (Russian: Евгений Леонидович Кринов, March 3, 1906, Otyassakh, Tambov region – January 2, 1984), D.G.S., was a Russian astronomer and geologist. ... This article or section does not adequately cite its references or sources. ...

Planet V

Main article: Planet V

Planet V is a hypothetical planet thought by NASA space scientists John Chambers and Jack Lissauer to have once existed between Mars and the asteroid belt, based on computer simulations. The computer modeling findings of Chambers and Lissauer were presented during the 33rd Lunar and Planetary Science Conference, held March 11 through 15, 2002, and sponsored by NASA and the Lunar and Planetary Institute.^[9] For the Vanbrugh College dance party, see here. ... For the Vanbrugh College dance party, see here. ... The National Aeronautics and Space Administration (NASA) is an agency of the United States federal government, responsible for the nations public space program. ... Adjectives: Martian Atmosphere Surface pressure: 0. ... For details on the physical properties of bodies in the asteroid belt see Asteroid and Main-belt comet. ... The Lunar and Planetary Science Conference (LPSC), jointly sponsored by the Lunar and Planetary Institute (LPI) and NASA Johnson Space Center (JSC), brings together international specialists in petrology, geochemistry, geophysics, and astronomy to present the latest results of research in planetary science. ... The Lunar and Planetary Institute is a NASA-funded research institute, dedicated to studies of the solar system, its evolution and formation. ...

Hypothetical extrasolar planets

See also: extrasolar planet and list of unconfirmed exoplanets

• PSR 1829-10's planet, proposed by Andrew Lyne of University of Manchester on July 24, 1991, was retracted in 1992. A combination of an inaccurate position for the pulsar and a timing model approximating the Earth's orbit about the Sun with a circle yielded processed data resembling that which would have been expected from a pulsar planet with an orbital period of half a year.^[10]

• PSR 1257+12 D, the proposed fourth planet in the first extra solar planetary system, was retracted due to further detection refinements. It has subsequently been replaced by a proposal for a comet.^[11]

• A microlensing event in 1996 of the gravitationally lensed quasar Q0957+561, observed by R. E. Schild in the A lobe of the double imaged quasar, has lead to a controversial, and unconfirmable speculation that a 3 Earth mass planet is possibly in the unknown lensing galaxy, between Earth and the quasar.^[12]

An extrasolar planet, or exoplanet, is a planet beyond the Solar System. ... This is a list of unconfirmed extrasolar planets. ... PSR 1829-10 is a pulsar located in the Scutum Constellation. ... Andrew G. Lyne (born 1942) is a British physicist. ... The University of Manchester is a university located in Manchester, England. ... July 24 is the 205th day of the year (206th in leap years) in the Gregorian calendar. ... Year 1991 (MCMXCI) was a common year starting on Tuesday (link will display the 1991 Gregorian calendar). ... Year 1992 (MCMXCII) was a leap year starting on Wednesday (link will display full 1992 Gregorian calendar). ... Adjectives: Terrestrial, Terran, Telluric, Tellurian, Earthly Atmosphere Surface pressure: 101. ... The Sun (Latin: Sol) is the star at the center of the Solar System. ... An artists conception of PSR 1257+12s system of planets Pulsars are rapidly rotating neutron stars. ... PSR 1257+12 (also catalogued as PSR B1257+12, PSR 1300+1240, or PSR J1300+1240) is a pulsar located 980 light years from Earth. ... An artists concept of a protoplanetary disc. ... The introduction to this article provides insufficient context for those unfamiliar with the subject matter. ... The Twin Quasar (Double Quasar) or Old Faithful is also known as Q0957+561, or QSO 0957+561. ...

Fringe, pseudo- and non-scientific hypothetical planets

Counter-Earth

Main article: Counter-Earth

This idea was first established by Philolaus when he reasoned that in order to keep the universe in balance their was a need for a Counter-Earth, Antichthon in Greek, a second Earth, identical but opposite to ours in every way on the other side of the Central Fire. Counter-Earth is an Earth-like hypothetical planet, usually sharing an orbit with Earth but on the opposite side of the Sun. ... Philolaus (circa 480 BC – circa 405 BC) was a Greek mathematician and philosopher. ... Counter-Earth is an Earth-like hypothetical planet, usually sharing an orbit with Earth but on the opposite side of the Sun. ... It has been suggested that this article or section be merged into counter-Earth. ...

If such a planet actually existed in our current scientific cosmology, as a spherical world that revolved around the sun, it would be permanently hidden behind the sun but nevertheless detectable from Earth, because of its gravitational influence upon the other planets of the Solar System. No such influence has been detected, and indeed space probes sent to Venus, Mars and other places could not have successfully flown by or landed on their targets if a Counter-Earth existed, as it was not accounted for in navigational calculation. Major features of the Solar System (not to scale; from left to right): Pluto, Neptune, Uranus, Saturn, Jupiter, the asteroid belt, the Sun, Mercury, Venus, Earth and its Moon, and Mars. ... (*min temperature refers to cloud tops only) Atmospheric characteristics Atmospheric pressure 9. ... Mars is the fourth planet from the Sun in the solar system, named after the Roman god of war (the counterpart of the Greek Ares), on account of its blood red color as viewed in the night sky. ...

Planets hypothesized by Zecharia Sitchin

Main articles: Zecharia Sitchin and Nibiru (hypothetical planet)

In recent years, the work of the amateur Semitic language scholar Zecharia Sitchin has garnered much attention among ufologists, ancient astronaut theorists and conspiracy theorists. He claims to have uncovered, through his own radical retranslations of Sumerian texts, evidence that the human race was visited by a group of extraterrestrials from a distant planet in our own Solar System. Part of his theory lies in an astronomical interpretation of the Sumerian creation myth, the Enuma Elish, in which he replaces the names of gods with hypothetical planets. However, since the principal evidence for Sitchin's claims lies in his own personally derived etymologies and not on any scholarly agreed interpretations (including scholars among the Sumerians themselves), his theories remain at most pseudoscience to the vast majority, if not the totality, of academics. ^[1] Zecharia Sitchins photograph from The 12th Planet Zecharia Sitchin (born 1922)[1] is a best-selling author of books promoting the ancient astronaut theory for human origins. ... The term Nibiru comes from the Sumerian cuneiform tablets and writings dating 5,000 years old. ... Zecharia Sitchins photograph from The 12th Planet Zecharia Sitchin (born 1922)[1] is a best-selling author of books promoting the ancient astronaut theory for human origins. ... Ufology is the study of Unidentified flying object (UFO) reports, sightings and other related phenomena. ... Paintings from Val Camonica, Italy, c. ... A conspiracy theory is a theory that defies common historical or current understanding of events, under the claim that those events are the result of manipulations by two or more individuals or various secretive powers or conspiracies. ... Sumerian ( native tongue) was the language of ancient Sumer, spoken in Southern Mesopotamia from at least the 4th millennium BCE. It was gradually replaced by Akkadian as a spoken language in the beginning of the 2nd millenium BCE, but continued to be used as a sacred, ceremonial, literary and scientific... Major features of the Solar System (not to scale; from left to right): Pluto, Neptune, Uranus, Saturn, Jupiter, the asteroid belt, the Sun, Mercury, Venus, Earth and its Moon, and Mars. ... Creation beliefs and stories describe how the universe, the Earth, life, and/or humanity came into being. ... Enûma Elish is the creation epic of Babylonian mythology. ... Phrenology is regarded today as a classic example of pseudoscience. ...

Sitchin's theory proposes the planets Tiamat and Nibiru. Tiamat would be a planet theorized by Sitchin to have existed between Mars and Jupiter. He postulated that it was a thriving world in a much differently shaped solar system, with jungles and oceans, whose orbit was disrupted by the arrival of a large planet or very small star (less than twenty times the size of Jupiter) which passed through the solar system between 65 million and four billion years ago. The new orbits caused Tiamat to collide with this object, which is known as Nibiru. The debris from this collision are thought by the theory's proponents to have variously formed the asteroid belt, the moon, and the current incarnation of the planet Earth. To the Babylonians, Nibiru was the celestial body or region sometimes associated with the god Marduk. The word is Akkadian and the meaning is uncertain. Because of this, the hypothetical planet Nibiru is sometimes also referred to as Marduk. Sitchin hypothesizes it as a planet in a highly elliptic orbit around the Sun, with a perihelion passage some 3,600 years ago and assumed orbital period of about 3,600 to 3,760 years or 3,741 years, he also claims it was the home of a technologically advanced human-like alien race, the Anunnaki, which would have visited Earth in search of gold particles. To meet Wikipedias quality standards, this article may require cleanup. ... The term Nibiru comes from the Sumerian cuneiform tablets and writings dating 5,000 years old. ... Adjectives: Martian Atmosphere Surface pressure: 0. ... Adjectives: Jovian Atmosphere Surface pressure: 20–200 kPa[4] (cloud layer) Composition: ~86% Molecular hydrogen ~13% Helium 0. ... See also Lists of astronomical objects Category: ... The term Nibiru comes from the Sumerian cuneiform tablets and writings dating 5,000 years old. ... For details on the physical properties of bodies in the asteroid belt see Asteroid and Main-belt comet. ... Adjectives: Terrestrial, Terran, Telluric, Tellurian, Earthly Atmosphere Surface pressure: 101. ... Babylonia was an ancient state in Iraq), combining the territories of Sumer and Akkad. ... Marduk (Sumerian spelling in Akkadian: AMAR.UTU solar calf; Biblical: Merodach) was the Babylonian name of a late-generation god from ancient Mesopotamia and patron deity of the city of Babylon, who, when Babylon permanently became the political center of the Euphrates valley in the time of Hammurabi (18th century... Akkadian (lišānum akkadÄ«tum) was a Semitic language (part of the greater Afro-Asiatic language family) spoken in ancient Mesopotamia, particularly by the Assyrians and Babylonians. ... Two bodies with similar mass orbiting around a common barycenter with elliptic orbits. ... This article is about several astronomical terms (apogee & perigee, aphelion & perihelion, generic equivalents based on apsis, and related but rarer terms. ... A year (from Old English gÄ“r) is the time between two recurrences of an event related to the orbit of the Earth around the Sun. ... The orbital period is the time it takes a planet (or another object) to make one full orbit. ... For the fictional Anunnaki from Demon: The Fallen, see Annunaki (White Wolf), the Outlanders series by Mark Ellis, and The Empire Chronicles Ancient Sumerian cylinder seal impression depicting the Annunaki. ...

See also

• List of unconfirmed exoplanets
• List of stars with confirmed extrasolar planets
• List of hypothetical astronomical objects
• List of Solar System bodies formerly regarded as planets
• List of fictional planets

This is a list of unconfirmed extrasolar planets. ... The following are lists of stars with confirmed extrasolar planets. ... Hypothetical astronomical objects are celestial bodies which some believe to exist. ... The table below lists Solar System bodies formerly considered to be planets: ^ Recently (2006) reclassified as a dwarf planet. ... The exploration of other worlds is one of the most enduring themes of science fiction. ...

References