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Q. I heard a friend of mine talking about the Tenth Planet. Can you please enligten me on this? — Henry K.
A. He refers to an undiscovered planet beyond Pluto.
Pluto is the ninth planet from the Sun. The so-called Tenth Planet sometimes is called Planet X. The letter X is the Roman numeral for ten.

Some astronomers think that Planet X, and maybe even more planets, will be found beyond Pluto. From what we know now, there is a large belt of comets and other planetoids orbiting the Sun in that far distant region of the Solar System beyond Pluto.

Dark planetoids. Recently, several mysterious large dark bodies has been found in the outer reaches of the Solar System orbiting the Sun at astonishing distances billions of miles beyond Earth. The newly discovered bodies are the most distant object yet found orbiting our Sun way beyond Pluto.

A second sun? By the way, there also have been tales of an undiscovered star forming a binary system with our Sun. It sometimes is referred to as Nemesis. If it existed, Nemesis and the Sun would be in orbit around each other. So far, there is no evidence of it. Of course, Nemesis is not the Planet X, which you asked about.

All of this has to do with our Solar System. Way beyond our own system is a vast number of other stars, which form our galaxy, the Milky Way. Lots of astronomers wonder whether there might be a system of planets around each of those stars. Isn't it all very exciting to think about?

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Large dark planetoids orbiting our Solar System  »»
Learn more about Pluto  »»
The Voyagers are beyond Pluto  »»
The Pioneers Are Way Out There  »»

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