Dear Robert and Audriana,

According to NASA, at this time there is no known Planet X or 10th planet in our solar system. Scientists have been looking for more than 150 years. It was believed that such a planet was required to explain the orbital characteristics of the outer planets Uranus and Neptune. Many searches have been performed and, to date, no evidence of such a planet has emerged. In addition, better information about the masses of outer planets has also now shown that no other planets are necessary to explain the planetary orbits. You can get a good historical account of the searches for “Planet X” by visiting http://seds.lpl.arizona.edu/billa/tnp/hypo.html#planetx

Did you know Pluto was called Planet X before it was discovered? Both Neptune and Pluto were discovered because astronomers carefully mapped the orbits of the other planets and found small deviations in their expected orbits. They then tried to calculate if the pull of another planet could cause those differences. It was a great victory for those astronomers when Neptune was discovered — it was the first planet discovered in modern times, the first planet that was not known to people for thousands of years. Pluto was especially hard to find because it is small, so its gravity causes only small changes in the other planets’ orbits, and also because it is faint and hard to find in a sky full of stars.

Ever since then people have wondered if there is yet another planet further out than Pluto. Astronomers have searched the tiny deviations in the planets’ orbits for clues. At one point, someone claimed that his calculations showed that Planet X had to be a big planet, way far out in the solar system, in orbit at a big angle to the rest of the solar system. But this was shown to be impossible — if it had existed it would have pulled apart the whole solar system!

Last things I found in space were some M&Ms floating in an air inlet filter!

Thanks for your question,
Aubie and Jim Voss