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Name: Unknown
Status: Other
Age: N/A
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Date: Prior to 1993

My students came into class yesterday claiming that they had heard that a new planet beyond Pluto was discovered. They said that the new planet was named Karla. I have seen nothing about this in the papers. Another teacher said she heard it on the news. Do you have any information about this supposed discovery?

Yes, I have heard something about a new planet beyond Pluto ... but not that it was named "Karla". I have a hunch, though, that the name will not stick, if indeed it was the name, simply because all the other planets are named after mythological figures and some consistency in naming is always in order. I also have the impression that this planet (called planet X when I read about it) had a retrograde orbit ... that is, it revolves around the sun in the opposite direction as all the other planets.

This seems to be a popular question! Careful searches, including an infrared sky survey by the IRAS satellite, have produced no evidence of the hypothetical Planet X. Some astronomers believe that the observed orbital irregularities which prompted the search for X were due simply to observational error in the "old" (say, pre-1900) data. Others object on theoretical grounds, claiming that a planet as massive as the hypothetical Planet X (4 or more Earth masses) just could not have developed so far out in the solar system. In order to explain the absence of evidence (including the lack of any "tug" on either of the Pioneer or Voyager probes due to an unseen planet) some proponents say that Planet X has an eccentric and/or highly inclined (relative to the ecliptic) orbit, so that it was close enough to the outer planets to produce the perturbations observed up until ~1930, but has since moved out in its orbit, away from the rest of the solar system, so that it cannot now be detected. If so, it will not come back to the "detectable" range for several thousand years. Given such a situation (we cannot observe it, and the reason for its proposal is in doubt), it is likely that most astronomers discount the existence of Planet X. Update -- the October issue of Astronomy magazine refers to a recent study by Myles Standish of the Jet Propulsion Lab. The study shows that"the irregularities in the orbits of Uranus and Neptune result from the slightly incorrect values for the masses of the giant planets used in previous studies. When Standish used more accurate values determined from data obtained by the Voyager spacecraft, the irregularities disappeared."

Ronald Winther

There could be a planet beyond Pluto, but there is currently no evidence for one. A small planet well beyond Pluto's orbit would be EXTREMELY difficult to detect.

John Hawley

Update - March 2011
In 2005, there was a new dwarf planet discovered past Pluto. As of August 2006, the dwarf planet was confirmed and named Eris. Eris is listed as a dwarf planet, as is Pluto.


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