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What is Planet X?

Some astronomers believe the orbits of gas giants like the planet Saturn indicate that a large Planet X exists at the edge of the Solar System.
Some researchers have argued that anomalies in the orbit of Neptune indicate that a large planet may exist in the far outer reaches of the Solar System.
Planet X is a planet that only so far theoretically exists beyond Neptune.
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  • Written By: Tricia Ellis-Christensen
  • Edited By: O. Wallace
  • Last Modified Date: 20 October 2014
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Planet X (pronounced as the letter, not the Roman numeral) is a hypothetical planet that has been searched for throughout the years by many astronomers. While searching for this planet, astronomers “found” Pluto, and Xena or Eris, all classified now as dwarf planets and not considered true planets. Planet X was not usually considered to be the 10th planet because when the search began for it, astronomy experts had only discovered eight. Instead the name merely means an unknown planet that exists beyond Neptune.

Neptune was identified as a planet because astronomers found oddities in the orbits of the Uranus, Jupiter and Saturn, which many believed had to be caused by a planet still father from earth and the sun. Some of the mathematical discrepancies in these planet’s orbits, and in Neptune itself, indicated the presence of another planet beyond Neptune. When Pluto was discovered in 1930, it wasn’t large enough to explain the orbital patterns of all four planets; thus science looked for something beyond Pluto, possibly a gas giant as large as Jupiter.

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For most of the 20th century, astronomers continue to postulate on the existence of Planet X, and tried very hard to find it. By the 1990s, one of the arguments against the existence of such a planet was that probes sent into space haven’t moved in a way that would suggest the strong gravitational pull of a Planet X. Another contributor to the demise of the Planet X theory is that the space probe Voyager 2 gave more accurate measurements of Neptune, which explained away mathematical irregularities in its orbit.

There are some scientists who still posit the possible existence of a Planet X, but have reimagined the concept of what the planet might be. Some suggest a brown dwarf star and not a planet. Other astronomers like Patryk Lykawka have made calculations that suggest we’ll determine for certain by 2013 whether such a planet exists.

The hypothetical additional planet has captured the imagination of many and appears in numerous science fiction movies, TV shows and books. Robert Heinlein’s novel The Puppet Masters suggests ten planets in the solar system, the last called Kalki. Animated characters like Duck Dodgers and some of the Transformers refer to Planet X. Fictional renderings of the planet may refer to the 10th planet or the hypothesized huge planet that we have not yet, and may never find, because it doesn’t exist.

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nanny3
Post 3

@oscar23 and @eviemae - I agree with both of you in that we aren’t really sure what is out there. But, there probably is not a planet x. (Sorry, guys.)

It just isn’t in the mathematics. The math that we had used to calculate the possibility of another planet was skewed, and we were wrong. Hubble got better numbers, and now we know that we were wrong. Plain and simple.

Besides, we’ve known about the other planets for thousands or more years. Isn’t it likely that we could find it by now? (Now watch; we'll find planet x in 2012 just because I opened my big mouth on wisegeek.)

Eviemae
Post 2

Even if Planet X isn’t real the way that we think it could be, you know that there has to be something else out there. We cannot possibly have any idea!

Heck, it was just a few centuries ago that we were furious that the whole universe didn’t revolve around us!

We know more than we ever did, but we aren’t that far removed from the notion that everything is here just for our purposes.

oscar23
Post 1

Love it! Planet X may or may not be real. The way I see it is that there is no way we can ever, not even in a million years, begin to know what all is out there.

I doubt we will we even have a good idea of what our own solar system is made up of in that amount of time! We're sidetracked too easily. Either that or Earth will just be a big part of history by then.

Space is just too big. But I think that it is very unwise to say that there definitely is no Planet X, for the simple fact that there are too many unknowns. For us to assume that we know all that there is to know is not only pompous and arrogant, but downright ridiculous!

Then again, until we find it, we cannot say that it is certainly real based only on theory. The unknowns are just too immense! And captivating, I might add.

Is Planet X real? Who knows!

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