new planet definition proposal

kmarinas86 · Aug 24, 2006

The 9 are not planets, they are worlds. So are the 90+ worlds we know as moons today. The term planet is used for a form of celestial racism. The universe is analog, not digital, so get wit da program ol' peeps and yougins.

Saiph · Aug 24, 2006

celestial...racism? riiiiight. <div class="Discussion_UserSignature"> --------------------SaiphMOD@gmail.com -------------------"This is my Timey Wimey Detector. Goes "bing" when there's stuff. It also fries eggs at 30 paces, wether you want it to or not actually. I've learned to stay away from hens: It's not pretty when they blow" -- The Tenth Doctor, "Blink" </div>

cuddlyrocket · Aug 24, 2006

"So does this new definition mean that Earth isn't a planet any more? Because 3753 Cruithne shares its orbit with Earth (along with NEOs that cross Earths orbit), so it could be argued that Earth hasn't "cleared the area" around itself." No, it couldn't be argued that the meaning of 'cleared the neighbourhood around its orbit' in the IAU definition of a planet is such that Earth has not cleared the neighbourhood around its orbit. The IAU definition of a planet states it must have 'cleared the neighbourhood around its orbit', but also that Earth is a planet. To be consistent, the precise meaning of 'cleared the neighbourhood around its orbit', whatever that may be, has to mean that Earth has cleared the neighbourhood around its orbit!

Saiph · Aug 24, 2006

while some objects still cross earth's orbit, the number is small compared to the amount of objects that share the orbital properties of say, ceres in the asteroid belt, or Pluto out in the KBO region. This definition, like all others one can apply to the situation, does not have a non-arbitrary component. You can't say it's all or nothing. You could go by mass...but where do you draw the line? You could go by density...but where do you draw the line? You could go by self-induced spherical shape...but where do you draw the line? You could go by composition...but where do you draw the line? You could go by orbital eccentricity...but where do you draw the line? The 8 planets defined by the IAU are objects well within this vague area, they aren't borderline cases. Pluto is pretty close to the edge on nearly all categories when you compare it to the other terrestrial planets. It's orbital region is relatively crowded with similar objects (akin to the asteroid belt), it's mass, density and composition are low, it's orbital eccentrity far higher than any other planet, and it's lumpier than any other one as well. <div class="Discussion_UserSignature"> --------------------SaiphMOD@gmail.com -------------------"This is my Timey Wimey Detector. Goes "bing" when there's stuff. It also fries eggs at 30 paces, wether you want it to or not actually. I've learned to stay away from hens: It's not pretty when they blow" -- The Tenth Doctor, "Blink" </div>

JonClarke · Aug 24, 2006

Pluto is not borderline when you consider that objects as small as 400 km in diameter can achieve hydrostatic equilibrium. Nor is sphericity arbiatry, because, providing it is based on hydrostatic equilibrium in is related to a fundamental change in the nature of a body's internal structure. In the same way as using boiling point of water as a thermal reference point because it represents a fundamental phase change. I suspect the third criterion of sweeping out the neighbourhood was because some astomers did not like the idea of several dozen planets. But it is nuts because it pays no attention to solar system evolution. In the end though 'drawf planet will become a sementic quibble at worst and a subcategory at best, just like gas giant and terrestrial planets are subcategories. Jon <div class="Discussion_UserSignature"> Whether we become a multi-planet species with unlimited horizons, or are forever confined to Earth will be decided in the twenty-first century amid the vast plains, rugged canyons and lofty mountains of Mars Arthur Clarke </div>

input22 · Aug 24, 2006

It seems to me that if one just took a step back and looked at it, it would distill down to including only those objects which are orbiting in the same plane (meaning they were made at the same time by the same forces), and that are larger than the smallest which fits the previous conditions. Pluto is out.

synecdoche · Aug 24, 2006

AP says: "Much-maligned Pluto doesn't make the grade under the new rules for a planet: 'a celestial body that is in orbit around the sun, has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a ... nearly round shape, and has cleared the neighborhood around its orbit.' "Pluto is automatically disqualified because its oblong orbit overlaps with Neptune's." So why isn't Neptune disqualified also?

ittiz · Aug 24, 2006

This is actually discussed in a different thread. From what I can see it does disqualify Neptune as well. The object is supposed to be 100 times larger than any other body that shares it's orbit, but Neptune is only 21 times larger than Pluto. Either it was over looked or they haven't told us what the precise definition is yet.

vandivx · Aug 25, 2006

<"He was a lot of in TV before revolution. Then journalist knew him, so they asked him frequently to come into TV, and about astronomy things, even after that. However he acts as a jerk in other activities, so he makes me uneasy. " /> k, that's fair comment, don't know much about his pre 89 career or personal qualities, you may be right for all I know as to the vote, I am happier with fewer planets than if it went the other way of too many of them, they could leave Pluto in though, for tradition's sake if nothing else vanDivX <div class="Discussion_UserSignature"> </div>

synecdoche · Aug 25, 2006

This 'clearing the neighborhood' business doesn't hold water. It's almost like some folks wanted to kick Pluto out, but couldn't come up with a great reason for doing so, and whipped this together at the last minute. If Pluto were exactly the same as it is now, only it were the size of Saturn, no one would be talking about disqualifying it because its orbit happens to overlap with Neptune's -- no one would say that that's not a planet. I'm fine with demoting Pluto if it's warranted...and I'm fine with having a thousand planets in our solar system if *that's* warranted (you don't really need to be able to recite them all). But the reasons behind the decisions need to make sense. This seems like a bad day for science. Also -- how is the average person supposed to read the phrase "dwarf planet" and somehow not conclude that this is in fact a planet that's small? They need a different term. (This is like declaring that, say, a soft drink isn't a drink. Of course it is, it's got the word "drink" in the name...)

cuddlyrocket · Aug 25, 2006

I would imagine that astronomers in favour of the IAU definition would say that Neptune is a planet despite the existence of Pluto because the latter is an object in a synchronous orbit with the former and such objects don't count for the purposes of 'clearing the neighbourhood' (as it is impossible for a planet to clear such an object - that's why it's in a synchronous orbit in the first place!).

raghara2 · Aug 25, 2006

The problem is it is completely arbitary. Arbitary definition with possibility of slicing off enought objects in any system, with great memorization potential. It's significantly better than an arbitary definition of cleared its neighbourd. Actually it's not completely arbitary. It results from multiple simulations of planetary system formation, and other stuff. When you have figure eight star orbit, the term cleared theirs neighbourd looks silly. Of course it would be nice to define moons, however planet system type 1, 2, 3 is often enough.

pogy · Aug 25, 2006

What an interesting thought, re-classifying Pluto. That makes me wonder. Maybe we need rules for classifying elements? For an atom to be classified as an element, it should be capable of being found at Standard Temperature and Pressure, and be capable of existing for at least 0.1 seconds without spontaneously fissioning or otherwise decaying to some other elemental state. Or how about a ship versus a boat. Or a car versus a truck.

sponge · Aug 25, 2006

Here is just a size comparison from 100000km away from each body. <div class="Discussion_UserSignature"> SPONGE </div>

planetceres · Aug 26, 2006

Size does and doesn't matter. Take Ceres, It's size is tiny compared to many moons of the system. Yet, it does orbit within a resonance. It has a similar rotation as the next few planets. It has a rather low eccentricity. It is a major mass within it's orbital resonance. It is a spherical body. Pluto/Charon Binary shares some of these traits. In the first Titius Bode, Saturn was considered part of what made the equation legit. In the New Bode, Saturn is the worst follower of the resonance as a percentage of distance. (About 4.8%) (New Bode is at 1Ceres) http://www.1ceres.com/

Saiph · Aug 26, 2006

The wikipedia community has gathered together a decent article on the more scientific analysis behind the rather vague term "clearing the neighborhood" or Orbital Dominance. <div class="Discussion_UserSignature"> --------------------SaiphMOD@gmail.com -------------------"This is my Timey Wimey Detector. Goes "bing" when there's stuff. It also fries eggs at 30 paces, wether you want it to or not actually. I've learned to stay away from hens: It's not pretty when they blow" -- The Tenth Doctor, "Blink" </div>

derekmcd · Aug 26, 2006

Seeing the actual numbers definately puts it into perspective. <div class="Discussion_UserSignature"> <div> </div> <div>"If something's hard to do, then it's not worth doing." - Homer Simpson</div> </div>

ittiz · Aug 27, 2006

I was reading posts on the Physorg forums and somone pointed out something interesting about all those supposed more than 100 exosolar planets. No one can really call any of them planets untill we know thier "zones" are cleared, which could take centuries to millennia. If the definition isn't revised this could be a mess for centuries. To this point only one exosolar asteroid belt has been detected and it's massive. Makes me wonder how many Mars sized non-planets are there?

sponge · Aug 27, 2006

In my opinion which most will not agree with< i believe a body should be named a planet if it contains an atmosphere, eg Titan should be included, Mercury should be dropped, i dont think the obits of such bodies orbiting the Sun shold not be how we define planets. Lets face it whats the first thing that comes to mind when someone says Planet? Well for me its atmosphere and weather conditions, just a thought. Now some of you will probaly say the moon has a very thin atmosphere and that my above statement is flawed, Well I cant see any atmosphere on the moon so I would describe it as a moon. Pretty simple way to look at it I think. <div class="Discussion_UserSignature"> SPONGE </div>

Saiph · Aug 27, 2006

first thing I think of when I hear planet: Orbits a star. First thing I think of when I hear moon: Orbits a planet. So Titan is a moon with atmosphere. <div class="Discussion_UserSignature"> --------------------SaiphMOD@gmail.com -------------------"This is my Timey Wimey Detector. Goes "bing" when there's stuff. It also fries eggs at 30 paces, wether you want it to or not actually. I've learned to stay away from hens: It's not pretty when they blow" -- The Tenth Doctor, "Blink" </div>

sponge · Aug 27, 2006

Congratulations, thats why you are on the Mission Control Team. You can obviously see logical patterns which can be clearly defined. <div class="Discussion_UserSignature"> SPONGE </div>

Saiph · Aug 27, 2006

Methinks that was sarcasm <img src="/images/icons/smile.gif" /> <div class="Discussion_UserSignature"> --------------------SaiphMOD@gmail.com -------------------"This is my Timey Wimey Detector. Goes "bing" when there's stuff. It also fries eggs at 30 paces, wether you want it to or not actually. I've learned to stay away from hens: It's not pretty when they blow" -- The Tenth Doctor, "Blink" </div>

sponge · Aug 27, 2006

LOL sorry I couldnt resist, it was one of those moments that you dont get many of. Cheers <div class="Discussion_UserSignature"> SPONGE </div>

jroswald2001 · Aug 28, 2006

I think what eally upsets me about the new definitions was that they decided against including Ceres, Pluto, Charon and and U2003 just because it would have increased the number of planets to an uncomfortable extent. This is hardly scientific, and purely sentimentral. The IAU have failed us because they stuck to sentimental, rather than scientific arguments. The number of planets should never me decided upon what "feels right", but merely on what "is". And if our way of perceiving planets and their numbers changes drastically, so be it. We need a proper taxonomy that also accounts for what are currently referred to as satellites.

harmonicaman · Aug 28, 2006

"I think what really upsets me about the new definitions was that they decided against including Ceres, Pluto, Charon and and U2003 just because it would have increased the number of planets to an uncomfortable extent." I disagree; I believe that grouping like objects together helps to disambiguate the Solar System. If we take the all inclusive "No iceball left behind"(1.) approach, we're going to run into the situation of finding objects that fall into a size range that is difficult to catagorize as either a planet or something else. I think keeping objects of similar pedigree grouped together is logical. Of course it isn't perfect, but what is? I also believe that keeping Pluto as a planet would have been the sentimental choice -- the IAU rightly chose to forgo sentimentality for hard-nosed practicality. The Solar System really is resistent to an exacting taxonomy... 1. Dr. Michael Brown, CalTech; discoverer of Xena.

new planet definition proposal

kmarinas86

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