He made the search by comparing two pictures of the same part of the sky. The photographs would be taken several weeks apart. The astronomer would then check both photographs. An object in the solar system could be identified if it appeared to move from its place in the earlier photograph.

However, the first search failed. In fact, he failed to recognize Planet X in a few photographs. He searched again for it several years later. Percival Lowell did not have the chance to discover Planet X. He died suddenly in November, nineteen sixteen.

(MUSIC)

VOICE ONE:

The search for Planet X did not restart at Lowell Observatory for years. Then in nineteen twenty-five, Guy Lowell, a relative of Percival, gained control of the observatory. He decided to seriously search for Planet X. He wanted to continue the work Percival had started.

In the following years, Percival's brother, Abbott Lawrence, provided money to build a special photographic telescope. The new telescope was completed in early nineteen twenty-nine.

That year, an observatory official, V. M. Slipher, offered a young man a job working with the new telescope. The young man's name was Clyde Tombaugh.

VOICE TWO

Mister Tombaugh got a job a Lowell Observatory after he sent drawings of his observations of Jupiter and Mars. He quickly learned how best to use the new photographic telescope at the observatory. He carefully planned his research to make the most of his time. On February eighteenth, nineteen thirty, he discovered an unusual object after less than one year of searching. The object moved slowly in the sky like a distant planet. Percival Lowell's Planet X had been found!