You may have heard that Pluto is no longer a planet and our Solar System is down to eight planets. But you may not know why Pluto is no longer among those massive rocks special enough to have the title of planet. Learn the basics about Pluto, from past to present, including some interesting facts that might come in handy next time you are playing a trivia game.

Pluto’s History

PlutoCredit: NASAIn the early 1900’s astronomers suspected there was something amiss in the Solar System. There seemed to be a disturbance in the orbit of Uranus, something other than Neptune, which they already knew about. Employees at the Lowell Observatory set out to find out what was making this impact on other planetary orbits, suspecting it was another planet. This new planet was named Planet X during the exploratory phase.

After much tedious work, Clyde Tombaugh discovered Planet X on February 18th, 1930. Tombaugh’s work ruled out the possibility that Planet X was an asteroid, which at the time then put it into the classification of a planet. The name for the ninth planet in the Solar System came from an 11-year-old student named Venetia Burney. There is much speculation that the planet is linked in various ways to the Disney character Pluto, but there is no distinct evidence to prove any of the theories.

Reclassification in 2006

For 76 years, Pluto was considered the smallest and furthest planet in the Solar System. Then in 2006, the International Astronomical Union (IAU) decided it was time to define the term planet. When they decided on the definition, it meant that Pluto was demoted to dwarf planet instead. The definition of a planet now includes requirements for how large it is in relation to its moons, its shape and if it dominates the solar neighborhood around the planet and its orbit, according to National  Each planet’s moons are much smaller than the planet itself, but Pluto’s moon is roughly half the size of the planet, making it too big to be considered a standard planetary moon.

One of the most remarkable things about the reclassification of Pluto, though, is the fact that many people refuse to acknowledge the change in title. For some reason, many people in a variety of global societies are too emotionally attached to the tiny former planet at the far edge of the Solar System. Even some astronomers that understand the reasoning behind the reclassification better than other people can still contend that Pluto is a planet.

What this Means for the Solar System

The Solar System we know, love and live in is down to just eight planets. Pluto was the smallest planet before it was demoted to dwarf planet so the current smallest plant is now Mercury. Schoolbooks all over the world had to be modified to address the change in Pluto’s status, but it is still a topic of discussion. Now, elementary school students learn about not only the planets, but also the dwarf planet that used to be among our Solar System’s bodies. One other reason Pluto is separate from the other eight planets is because it is the only one of the group that has not been visited by a space probe.