1. Why Isn’t Pluto a Planet Anymore?

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

3. 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

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

5. 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)

8. Lots of objects far out, comparable to Pluto

9. And their orbits are different:

10. 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.

11. How was our solar system formed?

12. 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)

14. 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

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