Pluto defines a Planet as being a Planet!

kheider · Sep 12, 2006

>defining an object by it's surroundings is nonsense. I know it's the practice done at moons, and I'm not fond of it. />What really counts about an object is of course how that object is. Not how many objects it's surrounded by! You are right that moons are defined by their surrounding DOMINANT (more massive) Planet. But currently (for better or worse) we define both planets and moons by their surroundings. I would much rather call the following 'Planets' before I would call Pluto a Planet: Ganymede (has its own magnetosphere), Titan (with an atmosphere that is 5x higher and 4x denser than the Earths), Callisto, Io (active volcanoes), The Moon, and Europa (subsurface water?) Europa is 3.8 times more massive than Pluto. From my chart (dia km; mass kg): Ganymede (5262 ; 1.48e23) Titan (5150 ; 1.35e23) Mercury (4880 ; 3.3e23) (smaller but more massive than Titan) Callisto (4800 ; 1e23) Io (3630 ; 8.9e22) The Moon (3476 ; 7.3e22) Europa (3138 ; 4.8e22) Triton (2700 ; 2.14e22) (orbits Neptune backwards, so it is probably a captured KBO) -- Kevin Heider

MeteorWayne · Sep 12, 2006

"Which is why in a few more years, the definition of plaent will return to the the traditional one, of a planet about Pluto';s size or larger that is in orbit aroudn the sun, more or less in the planet of the ecliptic. " I assume you meant plane of the ecliptic. That's one of the major problems with pluto. It is NOT in the plane of the ecliptic. It's inclination of 17 degrees is typical of dozens of objects of similar and smaller size, in 2:3 resonance with Neptune. They are called Plutinos, out of respect for it's staus of the first, and one of the largest, to be discovered. But it is one of an easily identifiable class of objects. To me the outer edge of the planets is Neptune, a Giant object in a circular orbit. Pluto is but part of the fluff outside of that. Yes, a bigger than average piece, but one of hundreds of objects in that size class. See Pluto Perspectives Part 1 for clarification. Neptune is hugely larger than ALL the objects beyond it. All the rest is rubble., Pluto's one of the larger objects but is in no way unique. <div class="Discussion_UserSignature"> But the Krell forgot one thing John. Monsters. Monsters from the Id. I really, really, really, really miss the "first unread post" function </div>

MeteorWayne · Sep 12, 2006

And if a Kuiper belt object of 3 earth masses is found, (noting new reply line), I would suspect it will have significant effects within the belt. Like orbit clearing. Maybe not , but we'll see. When it's discovered, we'll deal with it. Until then, a definition has been thrown down for battle, which is occuring. I return to my point. There at least is a definition to argue about. Those who wail about the "demotion" of Pluto miss the point. It is the archtype for the Plutinos, a class of dozens of objects. It's as interesting, and useful in understanding the solar system as it ever was. So stop whining, make your arguments and deal with it. My Pluto Perspective threads have laid out the data on where Pluto fits into the heirarchy of the solar system. Yet all the activity exists in the hysterical "you can't demote my damn planet" threads. Emotion is not science, IMO. Analysis is. <div class="Discussion_UserSignature"> But the Krell forgot one thing John. Monsters. Monsters from the Id. I really, really, really, really miss the "first unread post" function </div>

MeteorWayne · Sep 12, 2006

The plane of the ecliptic is within 4 degrees of the earth's orbit. (See Pluto Perspectives Part 3), except for Mercury, which has it's own path to existance to deal with. Very close to the sun, relativistic effects, blasted by solar wind. It's a miracle it survived. All the rest are in a very narrow plane until you get beyond Neptune. Beyond that, all the little chunks are spread all over the place, except for: Plutinos, 2:3 resonance with Neptune, inclininations from 15 to 20 degrees, Orbital Periods between 245-252 years. Pluto is the 2nd largest we've discovered so far. Classic Kuiper Belt objects: Circular orbits with periods around 280 years. Everything else is scattered all over the place in inclination, eccentricity, and period. So Pluto is part of the Plutino pie. <div class="Discussion_UserSignature"> But the Krell forgot one thing John. Monsters. Monsters from the Id. I really, really, really, really miss the "first unread post" function </div>

MeteorWayne · Sep 12, 2006

It was not a REdefinition, it was the first definition ever attempted. As any person would expect, it will spark discussion. That is what we are living through. Ain't it fun? <div class="Discussion_UserSignature"> But the Krell forgot one thing John. Monsters. Monsters from the Id. I really, really, really, really miss the "first unread post" function </div>

jakethesnake · Sep 12, 2006

Thank you and it’s gratifying to see someone get my point. Since this is what I do on a daily basis, quantify applicable variables that must translate into viable data, it’s a little frustrating to try and get this point across to others who are so overly caught up in their blind opinions all be it very knowledgeable ones, none the less it’s a lot of fun trying! I’m also aware that this point of view of quantification through progressive understanding is obvious to me it is apparently illusive to many especially the IAU. Hey go with the flow and try not to piss too many people off! <div class="Discussion_UserSignature"> </div>

search · Sep 12, 2006

"The Englishman Who Went Up a Hill But Came Down a Mountain" In Pluto's case should be: "The Englishman Who Went Up a Mountain But Came Down a Hill" Did anybody asked how all this story of IAU new definition and Pluto being a now a Dwarf Planet and not a Planet started? IAU Definition The main problem with the definition arises from the third element of the definition Clearing the neighbourhood Alan Stern and Harold Levison work in the Southwest Research Institute and wrote the following proposal to the IAU. (check the one paragraph before last on page 6 of this document) Alan Stern however did not agree with the IAU decision and sign a petition against it. He also is working on the New Horizons. Maybe it was not the most remarkable definition and surely it will be challenged in the near future but it is a definition and can be improved. As for Pluto not being a planet well I believe New Horizons can bring some insight on this. Until then they will continue to dance for us in the sky.

ldyaidan · Sep 12, 2006

As we learn more, our current understanding of things, and our definitions will have to change. I do, however, feel that the definitions should be consistent, in our own solar system as well as others. If the change in pluto's status has caused such an uproar, just imagine the chaos when it was announced that the world is round, not flat as previously thought! Rae

robnissen · Sep 12, 2006

I've decided that the IAU has made things too complicated. Here are three simple facts that I think resolve the issue: 1. Mercury is a planet (going back to ancient times). 2. Pluto was called a planet because when it was discovered it was thought to be Planet X and much larger than Mercury. 3. Size matters. If Pluto was one-mile in diameter, but had coincidentally formed as a sphere, I don't believe anyone here would think it should be a planet. Thus, a planet is anything the size of Mercury or larger that orbits its star. It is irrelevant whether it orbits close to the ecliptic and the shape of its orbit is also irrelevant. One criteria, size. Its simple, it works in all solar systems, and has a thousands years old historical basis. (Using Pluto as the arbitrary limit on planet size is not based on an historical basis but rather on an historical mistake.) Also children could easily understand it, and while there might be a couple of Mercury sized objects out in the KBO, its unlikely that there will be hundreds which is another problem of using Pluto as the arbirtrary size limit.

rhm3 · Sep 12, 2006

So if Callisto was orbiting the Sun instead of Venus, it wouldn't be a planet? Setting any numerical size limit is too arbitrary, and makes things weird when you have objects just slightly under the given limit.

jakethesnake · Sep 13, 2006

Wayne I think the word arbitrary needs a closer look and to arbitrarily classify anything in science for the purposes of analyzing and quantification there has to be some point of reference. This point of reference does not need to be fully understood and can be derived at by statistical of physical analysis usually it is a combination of both which are used to narrow down the variability of what is being studied. Example: DNA When a geneticist searches for an anomaly within a strand of DNA a statistical process is used to narrow down the search. After a probable location is found either physically observation and/or actual manipulation can be used to see and confirm whether or not the anomaly has been isolated. When a geneticist starts his search he takes certain factors in to consideration such as where within a strand of DNA does such a “hypothetical” anomaly typically reside. Then an “educated arbitrary” location is picked to start the search and through this isolation processes a more refined “educated arbitrary” location is chosen narrowing down where this anomaly resides. ------------------------------------------------------------------------------------------------------------ Webster’s online dictionary http://www.websters-online-dictionary.org/definition/arbitrary Arbitrary Adjective 1. Based on or subject to individual discretion or preference or sometimes impulse or caprice; "an arbitrary decision"; "the arbitrary rule of a dictator";"an arbitrary penalty"; "of arbitrary size and shape"; "an arbitrary choice"; "arbitrary division of the group into halves". ------------------------------------------------------------------------------------------------------------ The IAU chose an arbitrary cutoff causing Pluto to be declassified as a planet this cutoff is not only vague <div class="Discussion_UserSignature"> </div>

Philotas · Sep 13, 2006

I would much rather call the following 'Planets' before I would call Pluto a Planet: Ganymede (has its own magnetosphere), Titan (with an atmosphere that is 5x higher and 4x denser than the Earths), Callisto, Io (active volcanoes), The Moon, and Europa (subsurface water?) I don't have any wish list when it comes to object that I think should be planets, because I don't start at the objects, I start at the definition; how to make the best scientific definition? "Once" an object is round, it's scientific interest is increased. And that's what I think should define; it's worlds that are interesting in their own right. -Chris Edit: Another thing is that this new planetary definiton goes into science books, yet it is not scientific. That's lame; do the IAU actaully know what they've done? <div class="Discussion_UserSignature"> </div>

jakethesnake · Sep 13, 2006

I agree that when a celestial body has enough mass to pull it’s self into a spherical shape it’s worthy of having an arbitrary definition but, the IAU completely fell short when it tried to differentiate between a “Dwarf Planet” and a “Planet”! <div class="Discussion_UserSignature"> </div>

kheider · Sep 13, 2006

Jake wrote: >A planet1 is a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, (c) font color=orange>only if it orbits tilts no more than an angle of 17 degrees away from the plane of Earth's orbitfont color=yellow> or no greater than the plane of Pluto’s orbit and (d) only if its Diameter is no less than Pluto’s Diameter (2274 km). So Jake, according to *your own definition*, if we find a Gas Giant World and it has an orbital inclination of 20 degrees, it is NOT a planet. Talk about messing up the definition of a Planet. Jake also wrote: >For you information Pluto is a dwarf Planet according to IAU not a “plutinos”! Jake, the above is proof that you have not done all of your homework. Pluto is a 'Dwarf Planet', Plutino (2:3 orbital resonance with Neptune), TNO, KBO, and known formerly as a Major Planet. Science should be based on facts and progress. It should not be based on mistakes from the past such as when the Sun, Moon, Ceres, Vesta, Pallas, Juno, and Pluto were known as Planets. -- Kevin Heider

wonky · Sep 13, 2006

Jake, like I keep saying, the definitions need to be tweaked. The more I think about it, the more I think the planet/dwarf planet's geology needs to be taken into consideration--such as if the body has a differentiated interior.

jakethesnake · Sep 14, 2006

Wow, are you contentious or what? Take a chill pill guy! I along with others that are posting on this thread came into the “Pluto is or is not a Planet belief” with preconceived beliefs and opinions with at least an open mind also, wanting to educate myself further though discussion and debate. I have been swayed on several issues, originally I did not think that a definition was needed due to the lack of knowledge by the astronomical community but have since changed my mind (thanks to MeteorWayne). So with that in mind I will take you’re somewhat haphazard and less than polite commentary point by point. 1. “So Jake, according to *your own definition*, if we find a Gas Giant World and it has an orbital inclination of 20 degrees, it is NOT a planet. Talk about messing up the definition of a Planet.” If you would have taken the time to read what I wrote marked (09/13/06 01:07): If there is to be an “uneducated arbitrary” cutoff of were a “Dwarf Planet” ends and a “Planet” begins it should be Pluto!” The hypothetical definition that I wrote at the beginning of this post was basically saying that I also don’t want every KOB that is spherical to be defined as a “Planet” not that my definition should be used for bedim but, that does not get away from the fact that Pluto was demoted based on nothing that was and to use your words “fact or progress”. You keep sighting “What makes a planet” by Steven Soter and his definition of “Orbital Dominance” and I have read his paper. --------------------------------------------------------------------------------------------------------------------------------- By Steven Soter: “A planet is an end product of disk accretion around a primary star or substar. I quantify this definition by the degree to which a body dominates the other masses that share its orbital zone.” -------------------------------------------------------------------------------- <div class="Discussion_UserSignature"> </div>

kheider · Sep 14, 2006

Kevin wrote: Pluto is a 'Dwarf Planet', Plutino (2:3 orbital resonance with Neptune), TNO, KBO, and known formerly as a Major Planet. Jake wrote: Kevin the IAU resolution 6b, naming this population "font color=orange>plutonianobjects" failed by less than ten votes yet it failed so, I guess you’re the one not doing his homework! Jake, Plutino (click here for the definition) and Pluton are two different words! Jake wrote: You keep sighting Steven Soter and “Orbital Dominance” and yet you feel geology is an important aspect of what should be used to classify a “Planet” as do I. “Orbital Dominance” and geology are basically two completely different ways of categorizing planets. I am trying to be pratical in defining a Planet based on 'what it is' and to a more limited amount 'where it is'. After all, Titan is not a Planet, not because of 'what it is', but because of 'where it is'. I think a Planet should be unique enough that is should not share it's orbital range with other comparable objects, ie Pluto (30-50AU orbital range) AND Ceres. Geology (dynamics and physical history of an obect, the rocks of which it is composed, and the physical, chemical, and biological changes that the object has undergone or is undergoing) would be useful, but it is more difficult to do geological studies (differentiated interior) of remote objects than it is to infer orbital dominance. It will be a long time before we send a spacecraft to planetary contenders in the outer solar system, much less to any exo-planets. Here is a recent picture of <</safety_wrapper>

search · Sep 14, 2006

I like this thread. It is getting more and more colourful.

MeteorWayne · Sep 15, 2006

Our observatory is giving a presentation to the public next Friday "WHAT IS PLUTO? Though generally the question of Pluto has not been in the public consciousness, astronomy professionals and enthusiasts have been discussing this tiny world ever since its discovery 76 years ago. Aside from its size, issues of its unusual orbital properties and distant position have energized the topic despite Pluto's entry into the science and astronomical text books we have all grown up with. The question of Pluto's planetary status is involved, with no clear cut resolution. Naturally such a question with give birth to varied perspectives. To help sharpen the public's understanding of these perspectives and illuminate the reasons why a world we all grew up with as a planet is now considered something else the NJAA will present a spirited discussion on the topic. In depth exploration of the oddities of Pluto that led to its recent demoting will be presented along with an opposing point of view. What is Pluto? We hope to help attendees decide for themselves. NJAA Observatory, Friday, September 22nd. Rain or shine, free event open to the public. " Guess which side I'm arguing <img src="/images/icons/wink.gif" /> MW <div class="Discussion_UserSignature"> But the Krell forgot one thing John. Monsters. Monsters from the Id. I really, really, really, really miss the "first unread post" function </div>

kheider · Sep 15, 2006

WHAT IS PLUTO? NJAA Observatory, Friday, September 22nd Hi Wayne; You might want to explain to them that we had 18 Primary Planets back in 1849. -- Kevin Heider

MeteorWayne · Sep 15, 2006

Kevin, very cool, I will use that image as I slice up my buddy in this discussion <img src="/images/icons/smile.gif" /> What is the source on this? <div class="Discussion_UserSignature"> But the Krell forgot one thing John. Monsters. Monsters from the Id. I really, really, really, really miss the "first unread post" function </div>

kheider · Sep 15, 2006

Source for 18 Planets: 1. Go to http://spaceweather.com/ 2. In the upper right under "View archives:"go to Sept 14th, 2006, and click view. You will see: 18 PLANETS: Have you ever heard of the planet Hygea? It's listed in the 1850 Annual of Scientific Discovery along with 17 other planets. In those days, large asteroids such as Hygea, Ceres and Vesta were widely deemed planets. They appeared so in textbooks and scientific journals. Adding asteroids to the other known planets, Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune, gave a grand total of 18. The asteroids were eventually demoted. It was a long, drawn-out affair, marked by decades of disagreement and confusion. (Sound familiar?) By 1900, however, order was restored to the Solar System: the planet count was down to eight. -- Kevin Heider

MeteorWayne · Sep 15, 2006

Thanx, Kevin. [drool] <div class="Discussion_UserSignature"> But the Krell forgot one thing John. Monsters. Monsters from the Id. I really, really, really, really miss the "first unread post" function </div>

Philotas · Sep 15, 2006

Back then they didn't have any problems with that many planets, but today they have. <img src="/images/icons/rolleyes.gif" /> <div class="Discussion_UserSignature"> </div>

MeteorWayne · Sep 15, 2006

It's all in where and how you draw the line. When asteroids started cropping up all over, "they" decided that the rubble were not planets but asteroids. More or less as we find ourself today, except instead of 18, it's now over 100,000. And Pluto still teeters on the edge, even though it was discovered 80 years after that summary. I am currently updating my largest object list (Pluto Perspectives, Part 1) to include anything larger than 250 km. It's going to be a big list!! Maybe too big, I may choose a higher cutoff for what I post, but they are all going into my large object list. For anyone who is interested, it is an excel file, and I will provide it upon request. It's a work in progress, but I have a deadline of next Friday, so I have to have it done by then <img src="/images/icons/smile.gif" /> <div class="Discussion_UserSignature"> But the Krell forgot one thing John. Monsters. Monsters from the Id. I really, really, really, really miss the "first unread post" function </div>

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