Pluto Hasn't Completed One Orbit Since Discovery

When American astronomer Clyde Tombaugh first spotted Pluto in 1930, it began a new chapter in our understanding of the solar system. Since that moment, humanity has lived through the Great (Review) Depression, World War II, the Space Race, and the entire digital revolution. Yet, in that same span of time, Pluto has not even made it halfway around the Sun. Its journey is so immense that one Plutonian year lasts for 248 Earth years, a timescale that dwarfs a human lifetime.

This immense journey is a direct result of Pluto's vast distance from the Sun and the laws of orbital mechanics. The farther an object is from the Sun, the slower it travels and the longer its path must be. Unlike the relatively flat, circular paths of the major planets, Pluto's orbit is a stretched-out oval that is tilted at a steep angle. This path is so eccentric that for about 20 years of its long trip, it actually crosses inside the orbit of Neptune, making Neptune temporarily the most distant planet from the Sun.

Because of this slow, looping voyage, the distant world won't return to the same point in its orbit where it was discovered until March 2178. It is a humbling reminder that while entire generations pass on Earth, the cosmos moves on a much grander and more patient timescale. The first "year" of Pluto's discovery is still more than 150 years from being complete.