Pluto the Planet :D

[LittleBlueGaming]

A simpler system is a better system, but only if it does not sacrifice accuracy and relevance in the process

Yeah, that's what I said.

[YNM]

Probably we should ask the public "Do we want any planet category at all" first. I would say no, better to classify objects on their five orbital elements (only excluding anomalies) and their Tisserand wrt the second largest object, Jupiter. IMO if there's anything they want to call planet, rock-solid, is the four gas giants.

[vger]

Seeing as we have a probe there now... wouldn't it be good manners to ask Pluto for his opinion?

Secretly, I was hoping there might be a landscape feature that looked like 'giving the middle finger.'

[Brotoro]

No, if they are rock, and do not have a moving orbit then its still a rock. Asteroids often have other asteroids orbiting them... re read my list....doesn't make the asteroid a planet OR a moon.

What are you talking about? Ida has a perfectly normal elliptical orbit around the Sun, just as Pluto does.

- - - Updated - - -

This might be helpful to show just how big the gap is between the 8 current planets and Pluto/others. Yes, 100 is technically an arbitrary line, but it's an arbitrary line that makes a lot of sense.

https://plutovian.files.wordpress.com/2010/12/dwarf-planets.jpg

Nice plot. I especially like the usage of the technical term 'crap' there.

[ko1Stein]

While it makes sense that Pluto is not a planet, the sudden change was incredibly annoying.

Additional to the IAU's planet definition, there are two other things that bugged my:

1: Plutos "moon" Charon is so big that their CoM is outside pluto. Doesn't this make them a binary system?

2: I bet pluto will have completely different moons next time he passes by our solar system because his orbit passes through the Kuiper Belt. Consistency? Who needs that!

[YNM]

Binary asteroid is already there, it's not hard to get binary dwarf planet in I guess. Now it's a matter of naming... Do we get 134340 A for Pluto and 134340 B for Charon ? And how to refer the whole system, like, what's the parent object of Nix, for example ?

2: I bet pluto will have completely different moons next time he passes by our solar system because his orbit passes through the Kuiper Belt. Consistency? Who needs that!

Asteroid belt, which is far more crowded, still sees some objects with stable moons. I know everything goes at snail's pace out there, but that implies changing moons etc. is going at a snail's pace for a snail's pace. Bet you don't get that 'till like next few tens of millenia or so.

[Brotoro]

Ceres, Pallas, Juno, and Vesta were once classified as planets...so our solar system had 11 known planets in 1807 (and then 12 when Neptune was discovered). It was only the discovery of many more asteroids starting in the mid-1840s that got these four demoted to "minor planets" (asteroids) after half a century as planets.

I'm sure there were people at the time who were upset about the demotions. But there aren't any of those people left.

The same thing will happen with people upset about Pluto being demoted.

[ZetaX]

2: I bet pluto will have completely different moons next time he passes by our solar system because his orbit passes through the Kuiper Belt. Consistency? Who needs that!

What does "next time he passes by our solar system" mean¿ It's eccentricity is still only 0.248 or so, which is not that far away from circular.

And like the asteroid belt, the Kuiper belt is not as densely populated as bad SciFi movies suggest. Encounters are very rare, catching a new moon is really really rare, and loosing a moon as big as charon requires quite a massive object or much more time.

[vger]

This thread needs a little relevant humor.

NDT vs. Colbert discussing Pluto

[Kilmeister]

This thread needs a little relevant humor.

NDT vs. Colbert discussing Pluto

I miss Colbert so much. Even though NDT doesn't really go into any real detail, I wouldn't really expect him to.

[Dooz]

I think we should make the Definition for planets much simpler

HYPOTHETICAL SITUATION.

mimas sized object found inside mercury's orbit

Is it roughly ball shape? Yes

does it orbit the sun? yes

has it cleared the neighborhood? yes. well there is hardly any stuff down there to begin with.

And this small 200km object is now a planet, but should be a dwarf planet.

Definitely some problems with this system.

Instead of having these requirements.

how about a simpler one defined by size?

Is the object roughly ball shaped?

orbits the sun?

does the object dominate the region based on size.

must be pluto sized or larger.

[Superfluous J]

I think we should make the Definition for planets much simpler

HYPOTHETICAL SITUATION.

mimas sized object found inside mercury's orbit

Is it roughly ball shape? Yes

does it orbit the sun? yes

has it cleared the neighborhood? yes. well there is hardly any stuff down there to begin with.

And this small 200km object is now a planet, but should be a dwarf planet.

Definitely some problems with this system.

Instead of having these requirements.

how about a simpler one defined by size?

Is the object roughly ball shaped?

orbits the sun?

does the object dominate the region based on size.

must be pluto sized or larger.

I personally think there should be 2 criteria:

1) Is the body's shape dominated by gravity and centrifugal acceleration? (which sets a low mass that is arguably fuzzy but can be defined mathematically)

2) Is the body's mass low enough so it doesn't fuse the atoms in its core? (which sets a high mass that is again fuzzy but can be defined mathematically)

I'm willing to accept a 3rd criteria:

3) Is the body orbiting a star? (i.e., a body that fails the 2nd test but passes the first)

Using my criteria, the edge cases become interesting things to study. Using the IAU's criteria, the edge cases cause decades of faux debate about why don't you love Pluto.

Edited July 16, 2015 by 5thHorseman

[peadar1987]

Totally agree. For me, any body in hydrostatic equilibrium orbiting a star that is not undergoing nuclear fusion in its core is a planet.

Within planets, there should be subcategories. "Primary planets" should be those who have cleared their orbits, "secondary planets" those that have not (the term "dwarf planet" implies the criterion is size and size alone, which is not accurate). We can teach the primary planets and the most important/historically significant secondary planets in schools.

[lajoswinkler]

And I think some people should grow up.

[NFUN]

I think we should make the Definition for planets much simpler

HYPOTHETICAL SITUATION.

mimas sized object found inside mercury's orbit

Is it roughly ball shape? Yes

does it orbit the sun? yes

has it cleared the neighborhood? yes. well there is hardly any stuff down there to begin with.

And this small 200km object is now a planet, but should be a dwarf planet.

Definitely some problems with this system.

Instead of having these requirements.

how about a simpler one defined by size?

Is the object roughly ball shaped?

orbits the sun?

does the object dominate the region based on size.

must be pluto sized or larger.

If comes out greater than 100 for the object, it is a planet. If it comes out less than 100 for Mercury, it is no longer a planet. Simple.

//Stern-Levison Parameter

[Bill Phil]

Totally agree. For me, any body in hydrostatic equilibrium orbiting a star that is not undergoing nuclear fusion in its core is a planet.

Within planets, there should be subcategories. "Primary planets" should be those who have cleared their orbits, "secondary planets" those that have not (the term "dwarf planet" implies the criterion is size and size alone, which is not accurate). We can teach the primary planets and the most important/historically significant secondary planets in schools.

I agree. Although I would use Major Planer and Minor Planet instead.

[rkman]

Are dwarf planets and gas giants considered to be classes of planets separate from "planets", or are they subsets of "planets"?

If the latter, then Pluto is a planet just as Jupiter is a planet in in spite of being a gas giant.

[Nibb31]

Are dwarf planets and gas giants considered to be classes of planets separate from "planets", or are they subsets of "planets"?

If the latter, then Pluto is a planet just as Jupiter is a planet in in spite of being a gas giant.

Gas giants are planets. Tellurian planets are planets. Pluto, Eris, Ceres, etc... are not planets, they are dwarf planets.

[Xannari Ferrows]

Let's pull up a comparison, shall we? How many arms would I have if I called my legs arms? 2. Calling my legs arms doesn't make them such.

Pluto will always be a planet to me, I'm not saying otherwise. If you want to call it a dwarf planet, that's fine, but it's a planet when you talk to me.

[vger]

Let's pull up a comparison, shall we? How many arms would I have if I called my legs arms? 2. Calling my legs arms doesn't make them such.

Pluto will always be a planet to me, I'm not saying otherwise. If you want to call it a dwarf planet, that's fine, but it's a planet when you talk to me.

Is there really going to be that much of an issue going forward if people call Pluto a planet instead of a dwarf planet? Hard to say, because people bicker constantly over such insignificant issues.

Is it okay to call a dwarf planet a planet? I don't see why not. "Dwarf planet" even has planet in the name, which implies it is a type of planet. If someone says, "Look at that car over there," I doubt anyone has ever responded with, "That's not a car, it's an SUV."

[Nothalogh]

Can we land on it without rockbolting the lander down?

Can we orbit it?

Can we not realistically tow it into another orbit?

Does it have FREAKIN MOONS?

It's a planet

[Xannari Ferrows]

If someone says, "Look at that car over there," I doubt anyone has ever responded with, "That's not a car, it's an SUV."

This is one thing ​Of many I wish was true...

[HoloYolo]

Can we land on it without rockbolting the lander down?

Can we orbit it?

Can we not realistically tow it into another orbit?

Does it have FREAKIN MOONS?

It's a planet

Nope.

[rkman]

Gas giants are planets. Tellurian planets are planets. Pluto, Eris, Ceres, etc... are not planets, they are dwarf planets.

So of all the different kind of planets only dwarf planets are not a subset of planets.

And a planet the size of Pluto or Ceres that has cleared its orbit would not be dwarf planet - and a planet the size of Earth or Jupiter that has not cleared its orbit would be a dwarf planet?

Edited July 16, 2015 by rkman

[Dkmdlb]

Does it have FREAKIN MOONS?

Pluto, Charon, and all the rest orbit around a common barycenter which is out in empty space, not inside any of them. So...