14. Pluto never completed an orbit during its time designated as a planet
The existence of Pluto was suspected based on the application of Newtonian Mechanics for many decades before astronomers began combing the sky to find the ninth planet. In 1906 Percival Lowell, the founder of Arizona’s Lowell Observatory, began an extended search for the planet in the regions of the sky where he expected it to be found. He died in 1916, having failed to establish its presence. The search did not resume until 1929, due to legal complications between the observatory and Lowell’s widow. When it did a young astronomer named Clyde Tombaugh was assigned to the task. By early 1930, Tombaugh announced the discovery of the planet had been confirmed.
It was a worldwide sensation during the early 1930s. It was named for the god of the underworld, Pluto, and the fame of its name influenced Walt Disney to name a new character, Mickey Mouse’s dog, after the planet. A newly created element – plutonium – was so named in its honor. But 76 years later, following the discovery of numerous previously unknown orbiting bodies, the International Astronomical Union changed the definition of what can be called a planet. Pluto didn’t qualify. It became a dwarf planet. During its entire period of being known as a planet Pluto did not complete a single orbit around the sun – or even half of one. On earth, it was a planet for 76 years, on Pluto less than one.