the one armed scissor

Hypothetical astronomical objects are celestial bodies which some believe to exist. These objects might include planets or moons which are inferred to exist based on scientific evidence. Some have yet to be proven or disproven; others are now viewed as protoscience, pseudoscience or obsolete scientific theory. Some such as Tiamat and Nibiru, are fringe science largely grounded in astrological texts usually viewed as anthropological artifacts rather than scientific fact. Planets like Phaeton or Tiamat could be considered "lost lands" in the veign of Atlantis, but on a larger scale. Authors such as Zecharia Sitchin and Burak Eldem have used these ideas as the basis for numerous science fiction stories.


Hypothetical planets

Vulcan: planet proposed by Urbain Le Verrier to explain irregularities of the orbit of Mercury. Disproved by Albert Einstein.
Planet X: Planet proposed by Percival Lowell to explain irregularities in the orbits of Uranus and Neptune. Disproved by Voyager 2, though some scientists have revived it in a different form.
Theia: Mars-sized protoplanet believed to have collided with the Earth 4 billion years ago and formed the Moon.
Tenth planet: The various theories of a tenth planet in our solar system, when Pluto was considered the ninth planet.
Fifth planet: Historically, a handful of solar system bodies have been counted as the fifth planet from the sun. Under the present definition of a planet, this celestial body is Jupiter.

Others have included Ceres and a now destroyed planet which fringe scientists have variously termed Phaeton and Tiamat. Nibiru, a large planet or brown dwarf with a highly eliptical orbit of aproximatly 3,600 years. Similar to Tiamat, this is based on theories propounded by Zecharia Sitchin.

Hypothetical minor planets

Vulcanoid asteroid: field of minor planets thought to exist within the orbit of Mercury. Named for Vulcan
Kuiper cliff: sudden dropoff in the number of Kuiper belt objects observed beyond 55 AU. Possibly caused by the gravity of a large, unseen object.



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Hypothetical natural satellites

Mercury's moon, a nameless moon of Mercury, which for a short time was believed to exist
Neith, a purported moon of Venus, now known not to exist
Themisto, a moon of Jupiter discovered in 1975, but lost before sufficient observations of its orbit could be made. In 2000, its existence was confirmed and it became an official moon of Jupiter.
Chiron, a disproven moon of Saturn
Themis, a moon of Saturn, supposedly discovered in 1905, but later shown not to exist after all
Lilith, Earth's "dark moon," which is still used in astrology
Gaga, a satellite of Saturn which gravitational disruption caused by Nibiru's passing may have incited to move outside of Neptune and becomes Pluto.


Hypothetical brown dwarfs

Nemesis: binary companion to the Sun proposed by astronomer Richard A. Muller to explain an apparent regularity in mass extinctions throughout Earth's history. According to the theory, as it passes through our system's Oort cloud, its gravitational disturbance sends hordes of comets in towards the Sun, making the probability of an extinction level impact much higher.

Dr. John Murray of the Open University and John Matese of the University of Luisianaat 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

(source: wikipedia)