Why Isn’t Pluto a Planet Anymore?

Do they have something against Yellow Dogs or something? Maybe he’s just a little too friendly?

Fault of Mike Brown One of most important planetary astronomers Published book: How I Killed Pluto, and Why it Had it Coming. Things came to a head at International Astronomical Union Meeting (IAU) in 2006 Meeting had heated arguments and shouting matches His young daughter didn’t like it either

Why was this such a big Deal? This is where you guys try to answer (not all at once, please!)

We always knew something wasn’t quite right with Pluto. . . Very small, (two thirds the size of Mercury) Very far out Orbit is much more elliptical And not in the plane of the eight other planets Not always the ninth planet – it was inside the orbit of Neptune for about 20 years (1979 to 1999)

Lots of objects far out, comparable to Pluto

And their orbits are different:

If Pluto was going to be a planet, it was going to have a lot of company Asteroid Ceres Pluto’s own moon Charon Eris (formerly Xena), Greek God of Discord, was the final straw, because it was actually bigger than Pluto Would have meant between 3 and 20 new planets, possibly up to 200 later.

How was our solar system formed?

So What’s a Planet? In 2006, astronomers voted on a planet’s definition: Is in orbit around the Sun Has enough mass so that it assumes a nearly round shape Has cleared its orbit (of space objects)

So What’s Pluto? Dwarf Planet: Is in orbit around the Sun Has enough mass so that it assumes a nearly round shape Has NOT cleared its orbit (of space objects) Is not a satellite

What is The Kuiper Belt? Icy bodies in orbit past Neptune