Sad day for Pluto when it was no longer considered a planet! Ha.
Scientists decided it is not technically a planet a few years ago, after about 30 years of arguing over it! (Scientists can be very slow to make up their minds about things).
They first started to be doubtful because its pretty small for a planet, and because a few other similar small ‘planets’ were discovered far out in our solar system. With a bit more research – and thanks to some awesome telescopes – they were able to figure out that its actually a part of the outer limits of our solar system that has several of these tiny planets in it. And these tiny planets are called ‘plutoids’, and are not officially planets.
To make all of this a bit clearer, in 2006 the International Astronomical Union wrote up a very specific definition for a ‘planet’ – and Pluto didn’t qualify 🙁