Clyde Tombaugh discovered Pluto in 1930 at Lowell Observatory in Flagstaff. Here's how Pluto won - and lost - its planetary status.
He called this hypothetical world "Planet X." "In some ways, Pluto's more of a planet than some of the other established ...
Sad face emoji for Pluto. When I was a boy reading books about the Solar System, there was Pluto at the edge of the double-page spread in the middle of the book, the furthest planet from the sun ...