Everyone's favorite dwarf planet, Pluto, was discovered on this day in 1930.
The existence of a ninth planet was first suggested by Percival Lowell (who, fun fact, also thought Mars had a canal system built by aliens) in 1905, who noted that wobbles in the orbits of Uranus and Neptune had to be caused by something. While he figured out that the planet must be in a particular part of the galaxy, he never laid eyes on it himself.
But in 1929, at the Lowell Observatory in Arizona (founded by Percival himself), astronomer Clyde Tombaugh managed it. He used a new technique, combining photographic plates with a blink microscope, a tool that allows users to quickly switch between two images to compare them, and caught a glimpse of the freezing-cold planet located billions of miles away.
In 2006, of course, the International Astronomical Union disappointed the world when it stripped Pluto of its planetary status, recategorizing it as a dwarf planet because it doesn't clear the space around its orbit. That's OK: it'll always be a planet in our hearts.
Where can you learn more about Pluto? NASA, of course.
