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CorvusCamenarum

macrumors 65816
Dec 16, 2004
1,231
2
Birmingham, AL
Dont Hurt Me said:
Problem is they just never defined a Planet very well, I like to think of Planets as Big enough Rocks to have or had a atmosphere.

So what about moons that have atmospheres? Saturn's Titan and Neptune's Triton are the only ones I can recall offhand.
 

Queso

Suspended
Mar 4, 2006
11,821
8
CorvusCamenarum said:
So what about moons that have atmospheres? Saturn's Titan and Neptune's Triton are the only ones I can recall offhand.
Our own moon has an atmosphere, albeit an extremely thin one.
 

srobert

macrumors 68020
Jan 7, 2002
2,062
0
CorvusCamenarum said:
So what about moons that have atmospheres? Saturn's Titan and Neptune's Triton are the only ones I can recall offhand.

And what about the moons that are bigger than Mercury, an undisputed planet? (Ganymnede and Titan)

Those guys (astronomers gathered in Prague) are probably throwing the same arguments at each other ^_^
 

2nyRiggz

macrumors 603
Aug 20, 2005
6,161
76
Thank you Jah...I'm so Blessed
How much this will count as now....13? xena, sedna, the egg shape one(with two moons), and the one that looks like a brown seed(I love wiki)....Man just name everything they can see....you know whats funny...our moon doesnt have a name but other planets moon(s) does.....




Bless
 

Dont Hurt Me

macrumors 603
Dec 21, 2002
6,055
6
Yahooville S.C.
CorvusCamenarum said:
So what about moons that have atmospheres? Saturn's Titan and Neptune's Triton are the only ones I can recall offhand.
Lets call em planets:D Maybe it should be a size thingy, X- amount of mass or larger is a planet. All we have to do is define X
 

BlizzardBomb

macrumors 68030
Jun 15, 2005
2,537
0
England
To add more confusion to this: Plan for 12 planets

A planet could be defined as:
* The object must be in orbit around a star, but must not itself be a star
* It must have enough mass for the body's own gravity to pull it into a nearly spherical shape
 

miloblithe

macrumors 68020
Nov 14, 2003
2,072
28
Washington, DC
The biggest surprise to me is Charon. That's a bunch of crap if you ask me.

name (min dist to sun, max distance from sun, orbital period, diameter)

Pluto (29.7, 49.3, 248.1, 2306)
Orcus (30.9, 48.1, 247.9, est. 840-1880)
Santa (35.2, 51.5, 285.4, est. 1500)
Quaoar (41.9, 44.9, 286.0, est 989-1346)
Easter Bunny (38.7, 52.6, 308, est 1600-2000)
Xena (37.8, 97.6, 557, est 3000)
Sedna (76.2, 975, 12050, est 1180-1800)
Ceres (2.5, 2.8, 4.6, 950)
 

emw

macrumors G4
Aug 2, 2004
11,172
0
At least they have a fairly unambiguous definition of a planet. Going purely by an arbitrary size wasn't good, and this sounds pretty reasonable to me.

Of course, now they've used the whole "pluton" thing, which seems odd. It's a planet with a "weird" orbit, essentially.

The inclusion of Charon makes some sense, in that Pluto and Charon are apparently a "dual-planet" type system, where they orbit each other. Ceres to me is the odd one, since we've known about that one for a long time and have always classified it as an asteroid.

I also like how they say that we should still focus on the 8 "classical" planets and these other ones are just kind of there.
 

Chundles

macrumors G5
Jul 4, 2005
12,037
493
miloblithe said:
The biggest surprise to me is Charon. That's a bunch of crap if you ask me.

Yeah, it's just a big moon. It's in orbit around Pluto, not the sun.
 

miloblithe

macrumors 68020
Nov 14, 2003
2,072
28
Washington, DC
emw said:
The inclusion of Charon makes some sense, in that Pluto and Charon are apparently a "dual-planet" type system, where they orbit each other.

But that seems somewhat arbitrary to me. The earth and the moon orbit around eachother too don't they? It's just a matter of ratios. The larger the moon is relative to the planet, the more effect it will have on its motion, but where's the cut off point between moon and planet?

(note: I'm no astronomer, so if I'm missing the point I'm happy to be corrected).
 

emw

macrumors G4
Aug 2, 2004
11,172
0
miloblithe said:
But that seems somewhat arbitrary to me. The earth and the moon orbit around eachother too don't they? It's just a matter of ratios. The larger the moon is relative to the planet, the more effect it will have on its motion, but where's the cut off point between moon and planet?

(note: I'm no astronomer, so if I'm missing the point I'm happy to be corrected).
As I understand it, they included Charon because the combined center of gravity is outside of Pluto, which is not the case for any other planet-moon system. But I'm no expert.
 

clayj

macrumors 604
Jan 14, 2005
7,612
946
visiting from downstream
This new plan sucks noodles. Ceres as a planet? It's part of the Asteroid Belt, fer cryin' out loud!

Either leave things the way they are (9 planets), or demote Pluto and make it 8 planets. It makes sense that the inner four planets are rocky terrestrials and the outer four planets are gas giants. Pluto is an anomaly and always has been.
 

jsw

Moderator emeritus
Mar 16, 2004
22,910
44
Andover, MA
clayj said:
This new plan sucks noodles. Ceres as a planet? It's part of the Asteroid Belt, fer cryin' out loud!
Well, it is 933 km in diameter and contains 25% of the entire mass of the asteroid belt. It's not a small little rock. Some theories suggest it's the core of what was a larger planet (or whatever you'd call it) between Mars and Jupiter.

I think we're getting too hung up over historical terms when, really, a definitive definition of what a "planet" is would then enable us to classify things appropriately, and it wouldn't bother me to have the number of planets increase over time as we found more. Nor would it bother me to define "planet" as one of the nine current ones and just use a new terminology for everything else, so that Earth would for example, be a planet and a blarble (or whatever term we use) whereas Ceres would be an asteroid and a blarble.
 

clayj

macrumors 604
Jan 14, 2005
7,612
946
visiting from downstream
Well, if Ceres was the core of whatever used to be in Orbit #5, then it used to be a planet... and not a very big one, if it represents 25% of the mass of that alleged planet.

But at 933 km, Ceres is a lot smaller than a lot of the moons that orbit planets... our Moon, Europa, Titan, Io, Triton, Ganymede, Callisto, etc.

I still think the count should be 9 or 8. I'm never gonna refer to Ceres as a planet, and Pluto/Charon and Xena barely qualify, but Pluto gets some benefit of the doubt because we've called it a planet for so very long.
 

iTwitch

macrumors 6502a
Mar 30, 2006
619
0
East of the Mississippi
Classical planets versus pluton? Ok, so the IAU needed something to do but Pluto has been a planet for a while now. Surely it's a classic? Oh well, can't fight progress or scientist with to much time on their hands. :)
 

thedude110

macrumors 68020
Jun 13, 2005
2,478
2
This is ridiculous.

People (the "they") should not be able to change fundamental truths once I'm older than 25. I just can't retain the information.

Like this thread. I'm totally going to forget about. Then in a few years I'll hear something on the radio about the "eleventh planet" and I'll be furious that nobody told me about it.
 

jsw

Moderator emeritus
Mar 16, 2004
22,910
44
Andover, MA
clayj said:
But at 933 km, Ceres is a lot smaller than a lot of the moons that orbit planets... our Moon, Europa, Titan, Io, Triton, Ganymede, Callisto, etc.
Yes... but it seems like you're more saying that it shouldn't be a planet because you weren't raised to consider it as such than because it's small.

Certainly the size ratio of Ceres to, say, Mercury is much higher than the ration of Earth to, say Saturn.

Or if size really matters, why consider anything but Jupiter, as it has well over two times the mass of all other planets combined?

Rigorously defining "planet" will answer the question, both for this solar system and for others.
 

emw

macrumors G4
Aug 2, 2004
11,172
0
clayj said:
Either leave things the way they are (9 planets), or demote Pluto and make it 8 planets.
Having a clear definition of what a planet is makes everything simpler to define and removes ambiguity moving forward as we discover more of these "things" in our solar system.

The fact that an object was misclassified in the past due to a lack of any clear cut methodology doesn't mean we can't correct ourselves. Science in most cases isn't absolute. Look at our view of dinosaurs and how that's changed over time as we've learned to read the data more effectively.
 

EricNau

Moderator emeritus
Apr 27, 2005
10,725
267
San Francisco, CA
We should wait until we discover intelligent life in other solar systems and ask them how they defined a planet. Then we can just use their system.

It'll be faster.
 

2nyRiggz

macrumors 603
Aug 20, 2005
6,161
76
Thank you Jah...I'm so Blessed
Wow..Pluto/Charon are "dual planets".....strange to my ears but so interesting. Do we address it as Pluto/Charon now or single them out.........I've never spent so much time on wiki as I'm doing now...indeed.


Note: little or big green or brown men are laughing at us now

Alien: stupid humans...haha ha



Bless
 
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