Pluto defines a Planet as being a Planet!

[Philotas]

They(astronomers, the IAU) didn't know how big the asteroids where, neither did they know when objects turn spherical under their own gravity. The only thing that is comparable from now and then, is the numbers. <br />If the original IAU proposal had succeded, we would have around 18 planets(12 at first) today.<br /><br /><br /><font color="yellow">When asteroids started cropping up all over, "they" decided that the rubble were not planets but asteroids.</font><br /><br />True; the IAU didn't promote scientific definitions back then either. <img src="/images/icons/crazy.gif" /><br /> <div class="Discussion_UserSignature"> </div>

 

[jakethesnake]

It would be nice to get that excel file from you so I can break it down statistically. If you would like I can send the modified file back to you but I’m not to sure you would want to bring it with you next Friday! I have done some preliminary stats on what you have posted already and from what I can see it doesn’t bode to well as far as your position goes!<br /><br />Of course I’m looking at what would differentiate the cut off between a “Dwarf Planet” and a “Planet” and everything I have looked at so far has been on average a linear distribution but a larger sample size would helpful to minimize the standard error I’m getting.<br /><br />I have been seeing an obvious trend as the mass of the object goes down there is more of a chance that the inclination and eccentricity will increase but this is also linear and I see no clear cutoff.<br /><br />I was thinking about combining some variable to come up with some comparative ratios and maybe doing some 3D scatter plots to see if something sorts out.<br /> <div class="Discussion_UserSignature"> <strong></strong> </div>

 

[ittiz]

Yeah it seems people can't seem to come up with a definition of a planet that doesn't have gray areas. I have come up with one though. Everybody will probably find it distasteful. I don't like it either but it is crystal clear.<br /><br />1: If it orbits a star or stellar remanent it's a planet regardless of size, location, orbit, or orbit of other bodies.<br />2: If it orbits with a planet or a moon and falls in a lesser class it's a moon.<br />3: If it falls in the same class it's a double planet if it orbits with a planet or double moon if it orbits with a moon.<br />4: The body must not have fusion due to compression or heat.<br />(Thanks to CuddlyRocket for pointing out that I forgot to mention criteria 4)<br /><br /><br /><br />This definition would pretty much clear up all the ambiguity with our current knowledge of solar systems. It would also avoid the problems some bodies being moons for one part of there orbits and planets for the other. Classes would be needed and I would suggest one similar to what we have already: <br /><br />Class One, Asteroidal World: Every thing with to little mass to be round would be an Asteroidal Planet or Asteroidal Moon. Pretty much everything smaller than Mimas would fall in that category. <br />Class Two, Dwarf World: If it has enough mass to be round but doesn't have enough mass to hold a carbon dioxide atmosphere (the heaviest naturally <b>abundant</b> gas) at the standard temp of 273.15K^o (0C^o, 32F^o) precluding outside influences (example: solar wind) it's a Dwarf Planet or Dwarf Moon. Pretty much all round bodies with less mass than Mercury would fall into that category.<br />Class Three, Terrestrial World: If it has enough mass to hold a carbon dioxide atmosphere at the standard temp of 273.15K^o precluding outside influences but doesn't have enough mass to hold a helium atmosphere at the standard temp of 273.15K^o precluding outside influences it's a terrestrial Planet/Moo

 

[jakethesnake]

I don’t find your solution distasteful and although it is a physical way of describing a “Planet” which I prefer over a spherical body being able to “clearing it’s neighborhood” I would prefer a planetary definition that predominately includes some sort of geophysical properties, such as how mass plays a roll at various levels of gravity but, this is not understood well enough at this point nor do we have the capacity at this time to fly out to all these objects and actually know their compositions, which has been pointed out on this thread.<br /><br />I think the color “Grey” is the color of the day for a while or at least many years!<br /> <div class="Discussion_UserSignature"> <strong></strong> </div>

 

[cuddlyrocket]

Lots of stars orbit stars, and would therefore be planets by criteria 1 of your definition.<br /><br />Which part of the atmosphere are you measuring the temperature at? (As the temperature changes with height and latitude.)

 

[MeteorWayne]

Very similar to what I'm doing, Jake, but for today, it's strictly data entry.<br />I was surprised at how many objects there really are with ESTIMATED sizes greater than 250 km! <div class="Discussion_UserSignature"> <p><font color="#000080"><em><font color="#000000">But the Krell forgot one thing John. Monsters. Monsters from the Id.</font></em> </font></p><p><font color="#000080">I really, really, really, really miss the "first unread post" function</font><font color="#000080"> </font></p> </div>

 

[jakethesnake]

You know what they say, “Absolute power corrupts absolutely” and I believe the IAU has most certainly reached this stature as have many different forms of governments and institution but the caveat is, we the people have these types of venues in which to bring their discretions to light! Isn’t it great, ye ha!!! <div class="Discussion_UserSignature"> <strong></strong> </div>

 

[ittiz]

Yeah one thing I forgot to mention was no fusion. But I do mention it at the end of the post as part of the planet classes.<br /><br />You don't have to worry about measuring the temperatures of these bodies. We already know the speeds of these gases at standard temperature. The temperature of the gas is determined by the average speed of the gas particles. Since we know what a speed distribution curve looks like we can calculate if the body can hold a gas at a given temperature. All you would have to do is determine the mass and radius plug it into a computer and the computer would tell you if that body could hold a particular gas at a particular temperature. The actual temp of the object wouldn't matter so there would be no need to measure temperature.<br /><br />stevehw33: If there are any factual inconsistancies in my post please point them out so they can be corrected.

 

[Philotas]

<font color="yellow">It is NOT a matter of fact that Pluto is or is not a planet. It is an arbitrary and unecessary redefinition is all, a break from a traditional and useful definition.</font><br /><br />And that's sort of what I've been saying since the beginning of the discussion.<br /><br /><br /><br /><font color="yellow">Again, will Those who promote this redefinition of planet Personally pay for the costs of re-reading all those thousands of science and other reference texts and then specifically Pay for the Costs of making the changes in type, etc., for all those hundreds of publishers in this arbitrary redefinition of planet? <br /><br />Will you, personally, pay for all the 10's of thousands of texts' changes needing to be made in Hundreds of languages and over 100 nations? <br /><br />Will you put your money where your position is? </font><br /><br />Science books should contain science, not 100% arbitrary planetary definitions. What seperates a planet from a minor planet is roundness, and thus also differentiation. That's science, and that what should be said in the text books. It's irrevelant how many planets we have and what they're called; but why they should be called planets, is what that's that's interesting.<br /> <div class="Discussion_UserSignature"> </div>

 

[derekmcd]

Steve... I agree with what you are saying and understand the point you are trying to make, but using the cost of textbooks is not really relevant.<br /><br />Science books, in particular, are plagued with factual errors, outdated info, misconceptions, compromises, and myths. <br /><br />I should think that I think that if some of the physics as to the reasons for the change were included, then absolutely it is worth the cost if it furthers the students education. And while the publishers are adding these 'arbitrary' changes, they might fix a few other things.<br /><br />Textbook publishing is, unfortunately, a competitive business that occasionally gets politics and religion involved to the detriment of the student.<br /><br />I haven't reviewed any science textbooks recently, however I do recall Pluto is commonly referred to as the 'farthest planet from the sun'. With that said, if changes in textbooks referring to the definition of planets somehow includes the reasons WHY it was changed, the education can be furthered and is no longer simply 'arbitrary'. <div class="Discussion_UserSignature"> <div> </div><br /><div><span style="color:#0000ff" class="Apple-style-span">"If something's hard to do, then it's not worth doing." - Homer Simpson</span></div> </div>

 

[MeteorWayne]

I've tried to make this point to Steve before and he has ignored it.<br /> <div class="Discussion_UserSignature"> <p><font color="#000080"><em><font color="#000000">But the Krell forgot one thing John. Monsters. Monsters from the Id.</font></em> </font></p><p><font color="#000080">I really, really, really, really miss the "first unread post" function</font><font color="#000080"> </font></p> </div>

 

[ittiz]

Although I do agree that the new definition is bad, I don't think the "text book problem" is a problem at all. Most text books these days have new editions released every few years or so. If you ever went to college you will remember that often you had to buy your texts brand new because they switched to the newest edition that semester. Discoveries are being made everyday in science and the textbooks are being rewritten constantly to accommodate them. The changes will just be included in the next edition of each text, which were going to be released anyway.

 

[cuddlyrocket]

"I'm no apologist for the old boys who've arbitrarily and unwisely changed a workable and traditional definition, a redefinition based upon the flimsiest of reasoning, which looks more like sophistry, than good science, and increasingly so."<br /><br />With all due respect, this is hyperbole. It is gratuitously offensive and inaccurate. You are at liberty to disagree with the IAU's definition, but that does not give you the right to libel people just because they disagree with you.

 

[silylene old]

I still think my definition is best, and I repeat it again. I first posted this 4 yrs ago before the SDC crash, and reposted it into other threads, and I post it again.<br /><br />This set of 5 simple rules still works best, IMO, and covers everything known about our solar system, recently discovered non-solar planets, and everything which may occur elsewhere in the universe:<br /><br /><font color="yellow">1) A planet circles a star or stars. If it does circle another planet, it is also considered a planet if the barycenter is above the surface of both objects ('double planets'). <br /><i>and</i><br />2) The maximum mass is below the threshold to sustain deuterium fusion, which is about 13x mass of Jupiter. <br /><i>and</i><br />3) A planet's is largely composed of 'normal' matter. It is not a mini-black hole, nor a mini neutron-object, etc. (not that any of these are known or perahps even possible with our current models of physics). This is actually a tough definition, for as the mass exceeds about 2x Jupiter, Coulombic forces between atoms in the object core will be inadequate to prevent atomic nuclei from compressing enough to form "electron degenerate matter" (when electron degeneracy pressure exceeds coulonbic repulsion). Adding additional mass to an object between 2x Jupiter and 13x Jupiter actually makes the object's radius get smaller due to forming additional electron degenerate matter in the core. As a result, masses between 2x Jupiter and 13x Jupiter are partially composed of not 'normal' matter. I am not certain of the dividing line here, but for now if less than 50% of the body's matter is denegerate, call it a planet.<br /><i>and</i><br />4) A planet has enough mass to gravitationally assume a spherical or ellipsoidal shape. <br /><i>and</i><br />5) A planet is at least as big as Pluto. This is arbitrary, cultural, historical and controversial. A dividing line has to be made somewhere.<br /></font>/safety_wrapper> <div class="Discussion_UserSignature"> <div class="Discussion_UserSignature" align="center"><em><font color="#0000ff">- - - - - - - - - - - - - - - - - - - - - -</font></em> </div><div class="Discussion_UserSignature" align="center"><font color="#0000ff"><em>I really, really, really miss the "first unread post" function.</em></font> </div> </div>

 

[jakethesnake]

Textbooks on average are replaced every 6 to 8 years in the US and less often in third world countries so, this is unquestionably a very expensive rewrite. This expense will ring very loud as the money starts being doled out and I’m sure plenty of articles will expound on the cost of this Pluto decision. <div class="Discussion_UserSignature"> <strong></strong> </div>

 

[wonky]

Jake, at first they wanted to add MORE planets. That would have required a re-write, anyway.

 

[jakethesnake]

This post has educated me enough to show a clear path as to what should have been done. The title and suggestion of this post “Pluto defines a Planet as being a Planet!” still remains in my mind as a correct assessment of what should have been done in the first place.<br /><br />One very good thing has occurred with the demotion of Pluto that was unfortunate to witness and that is it highlights the erratic and dysfunctional way the IAU operates.<br /><br />I have thrown down the question (what differentiates a “Planet” from a “Dwarf Planet”) on the table and not one single satisfactory answer has arisen from 162 replies and almost 4000 views!<br /><br />I understand the problem that the astronomical community has with the headache of finding all these new KBO’s but, to set a cutoff which excludes Pluto as being a Planet is a very costly decision that has little to do with science.<br /><br />The IAU couldn’t bring itself to admit what is the obvious and that is they just don’t know what a planet is so their pride came before the truth and this is to their disgrace!<br /><br />I believe the IAU should have left Pluto as a planet and not added any more planets to our solar system with the emphasis that the planet issue needs to be researched further.<br /><br />If you don’t know don’t add to the confusion!<br /><br />If you don’t know leave it alone until you do!<br /><br />If you don’t know admit it!<br /><br />If you don’t know don’t cost everyone a lot of money pretending you do!<br /> <div class="Discussion_UserSignature"> <strong></strong> </div>

 

[alokmohan]

Astonished at at the farce at renaming a planet.If any body has read astronomical popular papers for last few years he would be glad at this decision .The seeds of this thought is for decades.Most of the posters donot seem to have been careful on this point.

 

[ittiz]

Except I don't think they will rewrite until they are scheduled. Also my experience with college text books is they are rewritten about every three years. Although I don't know how long it takes for gammer school and high school texts.

 

[robnissen]

I agree with your entire post, except for item 5:<br /><br />"5) A planet is at least as big as Pluto. This is arbitrary, cultural, historical and controversial. A dividing line has to be made somewhere."<br /><br />As I stated previously, the ONLY reason PLuto was ever called a planet in the first place was because of the massive error in its size estimate -- the so-called Planet X which was allegedly disturbing the orbit of Neptune. Rather than basing an admittedly "arbitrary . . . dividing line [that] has to be made somewhere" based on a historical mistake, the "arbitrary dividing line" should be based on the thousands of years old standard . . . namely a planet must be the size of Mercury.

 

[robnissen]

Your argument regarding the alleged costs of upgrading text books is a red-herring. You approve of planetary status for Eris/Xena. But changing text books to add planets, does not cost one cent less than changing text books to subtract planets.

 

[silylene old]

<font color="yellow">Rather than basing an admittedly "arbitrary . . . dividing line [that] has to be made somewhere" based on a historical mistake, the "arbitrary dividing line" should be based on the thousands of years old standard . . . namely a planet must be the size of Mercury. </font><br /><br />Don't you find this dividing line just as arbitrary as Pluto?<br />(I won't even begin to point out that for the vast majority of the time that this "thousand years standard" of planetary definition supposedly existed, that Mercury was not understood to be a spherical sun-baked crater-pockmarked mass of rock and metallic elements orbiting the sun...rather it was just a point of dimly seen light seen at dawn or dusk, speculated to be a god riding a horse driven chariot around the Earth, or, as the Mayan's thought, a skull-owl !)<br /> <br />Then I ask, imagine a future, perhaps 250 years from now after we have built and operated a huge telescope in orbit....and where we now have detailed knowledge of perhaps 25,000 extra-solar planets. I can guarantee that we will find that these 25,000 planets will range in size from sub-Pluto to 13x Jupiter in a near continuous distribution. And with our future insight, we will know that there will be no clear dividing line whatsoever at a size, be it Mercury or Pluto, to differentiate a planet from a non-planet. We will know that creating a dividing line is arbitrary, just as arbitrary as saying that "green" will be the word we define as the wavelength of 510 nm. Putting the dividing line at Pluto, rather than Mercury is just as reasonable as any else. There was no need to change the 80 yr old definition away from Pluto. <div class="Discussion_UserSignature"> <div class="Discussion_UserSignature" align="center"><em><font color="#0000ff">- - - - - - - - - - - - - - - - - - - - - -</font></em> </div><div class="Discussion_UserSignature" align="center"><font color="#0000ff"><em>I really, really, really miss the "first unread post" function.</em></font> </div> </div>

 

[jakethesnake]

Are you are saying that a standard from 1,000 years of technically inferior science should override a modern day standard?<br /><br />Once again I reiterate: <br /><br />I have thrown down the question (what differentiates a “Planet” from a “Dwarf Planet”) on the table and not one single satisfactory answer has arisen from 171 replies and almost 4100 views!<br /><br />I would suggest that with something such as Pluto holding its sentimental status for 76 years during which time we have been to the moon and back several times and have had a space telescope “Hubble” in orbit since 1989 that someone i.e. the IAU could have come up with something more definitive than a planet clearing its “neighbourhood”!<br /><br />The IAU chose an arbitrary cutoff causing Pluto to be declassified as a planet this cutoff is not only vague it is just an “uneducated arbitrary” cutoff due to the fact that to many planets would have to be added to our solar system. It is simply physically not known when a planet begins according to the IAU definition. <br /><br />1. The IAU’s definition of planet is a definition exclusive to only our solar system and this only highlights the lack of physical knowledge to what a planet is. <br /><br />2. The IAU arbitrarily categorizes what we see to break up the job of assessment. <br /><br />I believe the IAU should have left Pluto as a planet and not added any more planets to our solar system with the emphasis that the planet issue needs to be researched further.<br /><br />If there is to be an “uneducated arbitrary” cutoff of were a “Dwarf Planet” ends and a “Planet” begins it should be Pluto!<br /><br />If you don’t know don’t add to the confusion! <br /><br />If you don’t know leave it alone until you do! <br /><br />If you don’t know admit it! <br /><br />If you don’t know don’t cost everyone a lot of money pretending you do!<br /> <div class="Discussion_UserSignature"> <strong></strong> </div>

 

[MeteorWayne]

Since the new Pluto thread is getting no action, here's a little humor to the discussion.<br /><br />See this Foxtrot cartoon <div class="Discussion_UserSignature"> <p><font color="#000080"><em><font color="#000000">But the Krell forgot one thing John. Monsters. Monsters from the Id.</font></em> </font></p><p><font color="#000080">I really, really, really, really miss the "first unread post" function</font><font color="#000080"> </font></p> </div>

 

[jakethesnake]

I like it and, it says exactly what I’m seeing, only the enthusiasts care so, I guess we are in one of those exclusive clubs.<br /><br />To bad more people don’t care because we would have probably left the solar system by now and, if the masses did care the Pluto question would have already been answered long ago.<br /><br />Money doesn’t make the world go round but it certainly can take us to the stars!<br /> <div class="Discussion_UserSignature"> <strong></strong> </div>