There was supposedly a planet orbiting the sun outside of Neptune. This mysterious planet was to be the 9th planet from the
sun, and soon Pluto was discovered. Pluto did not fit the description as put forth by astronomers, so there had to be yet
another planet that fit the characteristics, the 10th planet, Planet X.
The man who started the search for this planet was Percival Lowell. He had died before he could find the planet that he was
looking for. The man who was the predeccesor of Lowell, Clyde Tombaugh, had continued searching, not finding Planet X, but
Pluto. The search still continued.
Yet, another discovery was made. Millions of objects, known as the Kuiper Belt, were found. There could be no planet after
this belt, so the lookout for Planet X was halted...for a while.
The Kuiper Belt doesn't go on forever, you know. It stops suddenly at 55 AU. There has to be something out there, past the
belt, big enough to be classified as a planet. We'll just have to wait and see and let the astronomers do the work!
Other objects have been found in the Kuiper Belt that could be considered planets. Once instance is 50000 Quaoar, or Quaoar.
It is found in the Kuiper Belt, it is bigger than Pluto, but many have disproved it as a planet. Another object is 90377 Sedna,
or just Sedna for short. It is very distant, too distant to be the Planet X, and is only two-thirds the size of Pluto. It's
not it. And last, 2003 UB313, dubbed Xena, was just discovered very recently. It is bigger than Pluto, and many believe it
is Planet X. Other discoveries include 2005 FY9 and 2003 EL61.