Yes, I know, I was rambling in my birthday vlog and the Pluto planet question fit perfectly, but then I was questioning if it was still not a planet after it was a planet... or if it went back to being a planet... anywho, it had to be answered.
According to solarsystem.nasa.gov Pluto was discovered in 1930 and was named our solar system's ninth planet! But then, all bets were off, other rocks bigger or similar in size were discovered and then the question became, "do we have like, a gazillion planets?" ok, not quite like that because they weren't using "like" like that yet... for real though, people got together and decided Pluto wasn't big enough to be a planet. So, in 2006, Pluto was demoted to a dwarf planet and our solar system went back to only having eight planets.