Pluto: the once and future planet?

Watching Neil DeGrasse Tyson on The Daily Show right now. Here's what I'm thinking:

Pluto has an atmosphere. It's frozen on the surface most of the time, but big deal - it's still there.

Pluto's orbit may be elliptical, but we've found exoplanets outside our solar system with even more elliptical orbits, and we're still calling them planets. Why treat Pluto any different?

Pluto also has three moons. Not too shabby for something that's supposed to be just another Kuiper Belt oddity. Did I mention that one of the moons is a comparative whopper?

I see where Tyson is coming from, but I think we need to give Pluto the respect that it deserves. Call it a planet, already.

:P

:cry:

Besides, Titan has an atmosphere that's way thicker than Pluto's.

:P

If it wasn't orbiting Saturn already, it would probably make a pretty cool planet.

Just watch out for that liquid methane rain. If the chill doesn't get you, the toxicity will. :P

Its almost as large as the earth

These are to scale.

:hi:

That man is most excellent! Then there's the roid scheduled for 2029, first I've heard of it.

-Hoot

Iä! Shub-Niggurath!

:silly:

The more the merrier.

Planets are masses of 'sufficient size' that are spherical and orbit a star...

Other than the one I'm currently standing on.

a planet must pass these three tests:

1. It must have enough mass and gravity to gather itself into a ball.
2. It must orbit the sun.
3. It must reign supreme in its own orbit having gravitationally “cleared the neighborhood” of other competing bodies.

Since Pluto orbits in the vicinity of other smaller objects, it has not “cleared the neighborhood” of other bodies. Therefore it is no longer classified as a planet. It is now considered to be a “dwarf planet”. There are two other designated dwarf planets, Ceres and Xena.

http://www.iau.org/public_press/themes/pluto/">Pluto: International Astronomical Union

Some of them do cross each other's orbits, but have yet to be downgraded.

IAU punted, plain and simple.

Pluto is a dwarf planet, which makes it still a planet. You could then say that we have 11 planets instead of 9, including Ceres and Xena.

very few of them are in identifiable solar systems, and I'm aware of none where the planets themselves have orbits that cross each others orbits. Elliptical orbits are no indication that they do cross each others paths, and considering that most of these planets are Superjupiters, it seems unlikely that any planets that crossed their paths would last very long.

One day it will decide what it wants to be.

and saw my first diagram of the orbital paths of the "nine" planets, I thought to my self: "That little one way out there on the end is not right."

Over the course of time we learn things. When we do, we adjust our classifications and understandings to make sense of them. For years they listed one of the asteroids as a planet. They used to think that galaxies were nebulae. We have to get used to it. It may be romantic and nostalgic to think of it as being in the same class as the planets, but facts don't bear that out. If everything that goes around the sun is a planet, we will have to get ready for a few thousand planets. We shouldn't get sentimental over an icy rock, but hen I suppose Columbus would have felt bad if he had been alive when we found out that the island of HIspanola is not China.