planet X

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Related to planet X: Pluto, wiggle, on one

planet X

Unofficial designation given by Percival Lowell to the predicted hypothetical planet he believed existed beyond the orbit of Neptune. Pluto was eventually discovered by Clyde Tombaugh in 1930, but it was not the planet with a mass seven times that of Earth that Lowell had predicted. The trans-Neptunian region of the Solar System is now believed to consist of a host of icy, rocky planetoids, including Kuiper Belt objects and a shell of frozen comets called the Oort Cloud.

Planet X

(religion, spiritualism, and occult)

In anticipation of discovering a planet beyond the orbit of Neptune, astronomers referred to the celestial body as Planet X. This planet, now called Pluto, was finally discovered in 1930. A common astrological practice is to assign a newly discovered body a tentative meaning that can be derived from associations with its name. (In the present case, the mythology of Pluto, the ancient Roman god of the underworld, was explored for initial clues about the planet’s astrological influence.) Astrologers then study the influence of the body in charts in which it is prominent (i.e., charts in which it is in very close conjunction with another planet or with an angle). After further study of these charts, the preliminary meanings are revised so that they align with the empirical effects of the new body. This astrological principle is based on the well-established observation that the names astronomers give to newly discovered celestial bodies are not coincidental—that by virtue of some kind of unapparent, synchronicity, non-astrologically inclined astronomers give astrologically significant names to things.

Astrologers have not generally considered, however, how alternative names—or, especially, older, abandoned ones—might shed light on the meaning of a celestial body. Pluto, for example, is associated with X rays, sex (which, in contemporary society, is “X-rated”), and the unearthing of what is hidden (as in the “X marks the spot” of treasure maps). These are all meanings of Pluto that could easily have been derived from reflection on the significance of the “X” in the designation Planet X. “X” is also the symbol for multiplication (the Pluto principle of sex “multiplies”). In Roman numerals, “X” is the number 10. If the asteroid belt is considered to be the remains of a planet, Pluto is the tenth-outermost planet in the solar system. It was also the tenth celestial body to be included in the delineation of astrological charts (after the Sun, the Moon, Mercury, Venus, Mars, Jupiter, Saturn, Uranus, and Neptune). Additionally, “X” is a common designation for Christ (as in Xmas), which links Pluto with the redemptive drama central to Christianity: Christ’s death on the cross (another “X”), followed by his resurrection (death and rebirth are both ruled by Pluto).

These are all commonly understood associations with the planet Pluto. There are, however, other, less explored associations with “X” that can also be connected with Pluto. “X” is, for example, the biological designation for the female chromosome that everyone carries—females carry two (XX), males carry one (X plus the male chromosome Y). Pluto is thus linked with the primordial female nature. “X” is also used to cross out errors (as in the expression, “to X out an error”), indicating a correcting principle not commonly noted in delineations of Pluto. More associations are possible when entries for cross, crossroads, etc., are explored in a good symbolism dictionary, as well as when such X-words as expose and exorcise are examined in a standard dictionary.


Littmann, Mark. Planets Beyond: Discovering the Outer Solar System. 2d ed. New York: John Wiley & Sons, 1990.
Room, Adrian. Dictionary of Astronomical Names. London: Routledge,1988.