On February 18, 1930, at the Lowell Observatory in Flagstaff, Arizona, a 24-year-old astronomer named Clyde Tombaugh was hunched over a special machine called a blink comparator. It flashed two photos of the night sky back and forth, and Clyde was looking for any tiny dot that had moved between them. Most dots, of course, were distant stars sitting still. But that afternoon, one little speck in the constellation Gemini hopped a tiny bit from one photo to the next. Clyde sat back, grinned, and called his boss in.
The speck turned out to be a new world circling our Sun, way out past Neptune. Newspapers around the planet ran the story on their front pages. An 11-year-old British girl named Venetia Burney suggested the name Pluto, after the Roman god of the underworld, and astronomers loved it. The name even started with the initials of Percival Lowell, the rich astronomer who had founded the observatory and predicted that a ninth planet must be out there. Clyde Tombaugh, who'd grown up on a Kansas farm and built his first telescope from a tractor's spare parts, became instantly famous.
For 76 years Pluto was officially the ninth planet, beloved by kids everywhere. Then in 2006 scientists decided Pluto was a little too tiny and reclassified it as a 'dwarf planet,' a decision that made plenty of people grumpy. In 2015 the New Horizons spacecraft zoomed past Pluto and sent back stunning pictures of icy plains, blue skies, and a huge heart-shaped feature, proving that the little world Clyde found is still full of surprises.
