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The Life and Times of Planet X?

Planet X is not out there

When I was younger I remember hearing about the discovery of a new planet dubbed Planet X.  At the time I heard about this “Planet X” it was supposed to be the tenth planet in our solar system.  But then, as time went on, I never heard about it again.  The years went by and I forgot about Planet X.  It’s like it exited the galaxy without a goodbye.  And then it seemed there was this resurgence in the name or in the very concept of Planet X.  A band came out with name Planet X that got my attention and then two films came out that dealt with a rogue planet: Lars von Trier’s “Melancholia” and Mike Cahill’s “Another Earth.”  So whatever happened to this new planet that seemingly came and went?  Whatever happened to Planet X?

First off, there have been many cases of a “Planet X” being discovered.  It all started back in 1846 when Neptune was discovered.  Neptune was the first planet discovered by way of mathematical predictions as opposed to actual observation.  These mathematical predictions were deduced when gravitational perturbations were seen in the orbit of Uranus.  When scientists thought these perturbations were the result of another planet past Uranus they calculated where this planet could be and, sure enough, they were right.

Well, with the discovery of Neptune many other astronomers thought it was a pretty cool trick and wanted to duplicate it by finding their own planets out there.  And as the years rolled on there would be many discoveries of “planets” past Neptune.  One such discovery was Pluto.  Before Pluto gained it’s official name it was called “Planet X” by Percival Lowell.  However, Lowell never actually found it in his lifetime, he only predicted it based on the mathematical data.  Pluto was actually discovered Clyde Tombaugh at the Lowell discovery and it was thought to be the “Planet X” hypothesized by Lowell.  There was just one problem: Pluto was way to small to take credit for the perturbations in the orbits of Neptune and Uranus.

Whatever was causing these irregularities it had to be big.  So the 1930 discovery of Pluto didn’t settle the Planet X debate.  The discovery of Pluto was more of a coincidence if anything.  Tombaugh’s persistent efforts to find Lowell’s prediction pointed him in the right direction but it was happenstance that brought Pluto to light.  The search continued for this large planet past Neptune that would explain the orbital perturbations.

As time went on there would be more predictions made about the existence of a “Planet X.”  One famous prediction in 1972 by astronomer Joseph Bradey was that there was a planet out there the size of Saturn that took 500 Earth-years to revolve around the Sun but its orbit was lopsided to Earth’s.  However, this theory wasn’t held in high regard.  Later, we’ll see, in 1989 it would be proven wrong.

Back in 1983 there was a report of a new planet.  This came about when a news source reported that a satellite used to make astronomical discoveries in infra red light spotted several unidentified objects.  At a press conferences a list of possibilities were given to explain these unidentified objects.  One of the possibilities was a new planet.  Of course, out of all the possibilities that were listed the news source ran with the tenth planet one.  Later it was found that these objects were distant galaxies and a dust cloud.  No planet was actually found.

Then in 1989 the Voyager 2 flyby established more precise observations of the orbits of Neptune and Uranus and discovered that the irregularities in their orbits didn’t exist.

Also, in 1993 the orbits of Neptune and Uranus were recomputed with all the new data found by space probes and, low and behold, when all the junk was taken out of the numbers the orbits of the two outer most gas giants didn’t have any perturbations in their orbits at all.

The gravitational perturbations was an inaccurate estimate and there was no need for a “planet x” to explain them.  So that should put things to a rest on Planet X, right?


In 2005 astronomers were looking over some telescopic images and found a large object out past Pluto.  This object would be called 2003 UB313.  And here’s the thing: it was the furthest object found in our solar system, it was fairly large (about a fifth the size of Earth), it takes 557 years to revolve around the Sun, and the orbit is a bit lopsided.  Sounds a lot like what Joseph Bradey predicted, right?

Well, not really.  This object, which would later be named Eris,  was much smaller than Brady had predicted and, again, was discovered by coincidence.

So what started off as a theoretical planet whose existence explained the presupposed gravitational perturbations of the outer gas giants has now morphed into a term used to define any largish body of astronomical interest in our solar system.

And so goes the life and times of Planet X.

NASA launched the New Horizons space probe which will fly past Pluto in 2015.  However, it’s not expected to discover any new mysterious objects.

New Horizons

—————————————- Sources:

Akwagyiram, Alexis “Farewell Pluto?” BBC News 02 August, 2005.

Delsanti, Audrey and Jewitt, David. “The Solar System Beyond The Planets” Institute for Astronomy, University of Hawaii NASA Astrobiology Institute, Cooperative Agreement No. NNA04CC08A. Office of Space Science.

Jewitt, David and Luu, Jane “Discovery of the candidate Kuiper belt object 1992 QB1” Nature 362 (1993): 730-732.

Stern, S. Alan and Colwell, Joshua E. “Collisional Erosion in the Primordial Edgeworth-Kuiper Belt and the Generation of the 30-50 AU Kuiper Gap” The Astrophysical Journal 490 (1997): 879-883.

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