Back in 2006, scientists voted on a new definition of the word planet and Pluto failed to meet it. They came up with this new definition because how they were defining it before was not accurate enough. So, Pluto is no longer a planet because it does not fit the criteria that they set out to make an accurate definition of what a planet is. This blog post will give you a little bit more information on why Pluto lost its planet label and why we now have 8 planets instead of 9. Pluto is a very interesting planet. It is the only one with a known rocky core, and it is its own planet in our solar system. But recently, Pluto was demoted to not even being considered a planet. Here's what happened: when scientists were trying to figure out what the word planet meant, they realized that they needed to make sure that there weren't any more objects that could be mistaken for planets because they really weren't planets by their definition. So that's what they did. They made a new set of criteria for the word planet and now we have 8 planets in our solar system. Pluto failed to be considered a planet because it wasn't big enough, nor did it orbit the sun in a circular motion. But don't worry! Pluto is still an interesting object, and it has its very own solar system called the Kuiper Belt in which it orbits the sun. And because it has its own solar system, it is still considered a planet and in the future, it will be a planet again. Here's what happened to make Pluto not a planet anymore: The word planet had been used for several centuries before scientists decided to officially set some criteria for how a planet is defined. So, when scientists decided that they needed to set the definition of planet they went back through the historic literature of planets and picked up on the ones that could have been mistaken for a planet.