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A hypothetical Solar System object is a planet, natural satellite or similar body in our Solar System 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. ==Planets== *Fifth planet (hypothetical), historical speculation about a planet between the orbits of Mars and Jupiter. * *Phaeton, a planet situated between the orbits of Mars and Jupiter whose destruction supposedly led to the formation of the asteroid belt. Nowadays, this hypothesis is considered unlikely, since the asteroid belt has far too little mass to have resulted from the explosion of a large planet. * * Planet V, a planet thought by John Chambers and Jack Lissauer to have once existed between Mars and the asteroid belt, based on computer simulations. * Planet X, a hypothetical planet beyond Neptune. Initially employed to account for supposed perturbations (systematic deviations) in the orbits of Uranus and Neptune, belief in its existence ultimately inspired the search for Pluto. Though the concept has since been abandoned following more precise measurements of Neptune's mass, which accounted for all observed perturbations, it has been re-applied to account for supposed deviations in the motions of Kuiper belt objects. Such explanations are still controversial, however. * Theia, a Mars-sized impactor believed to have collided with the Earth roughly 4.5 billion years ago; an event which created the Moon. * Vulcan, a hypothetical planet once believed to exist inside the orbit of Mercury. Initially proposed as the cause for the perturbations in the orbit of Mercury, some astronomers spent many years searching for it, with many instances of people claiming to have found it. The perturbations in Mercury's orbit were later accounted for via Einstein's General Theory of Relativity. * * Vulcanoids, asteroids that may exist within a gravitationally stable region inside Mercury's orbit. *Tyche, a hypothetical planet in the Oort Cloud supposedly responsible for producing the statistical excess in long period comets in a band.〔 The Independent, ("Up telescope! Search begins for giant new planet" ), Sunday 13 February 2011, Paul Rodgers 〕 Results from the WISE telescope survey in 2014 have ruled it out. *A hypothetical fifth gas giant originally in an orbit between Saturn and Uranus and that was subsequently flung out of the Solar System into interstellar space after a close encounter with Jupiter, resulting in transferred angular momentum that caused Jupiter to recede from the Sun and may have ensured the orbital stability of the terrestrial planets in the inner Solar System. It may have also precipitated the Late Heavy Bombardment of the inner Solar System.〔Lisa Grossman: "Lost planet explains solar system puzzle" ''New Scientist'': 01.10.2011: 14–15〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「List of hypothetical Solar System objects」の詳細全文を読む スポンサード リンク
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