Expert: Paul Wagner - 2/2/2011

Question
I am a college student and I am supposed to write a paper on "a topic of interest from science". I don't know if you will be able to get back to me in time, but I want to know why Pluto was kicked out of the solar system. I know it has to do with its size, orbit, and the fact that it hasn't cleared the space around it from all other orbiting bodies, but we've called it a planet since it was found, so why kick it out now? Also i've heard that they've now found that Pluto has 3 moons: Charon, Nix, and Hydra. Is this true? Back in high school my astronomy teacher argued with me about this, and I just want to know. Thank you for your time.

Answer
Hi Dixie

It all has to do with how we define planets--size, orbit, etc.  And the fact that we've found a couple of other bodies out there by Pluto that are also small, with eccentric orbits, and we don't want to call them planets...because they are small than the current list of planets, farther out, and have eccentric orbits.  Just like Pluto.  SO if we can't call THEM planets, why should we call Pluto a planet?

But if you do a web search, you will find tons of information about this topic...

Paul Wagner