Nobody's discussed presence/absence of an atmosphere. Maybe because Mercury doesn't have one. Any factor that eliminates Mercury won't do, because Mercury has been a planet since prehistoric times.<br /><br />Pluto does. Strangely, larger Ganymede and Callisto don't. Titan and Triton do. According to the N14/N15 ratios on Titan measured by Cassini, about 80% of Titan's atmosphere has evaporated. Unknown whether Xena has an atmosphere, but I bet right now it doesn't. It might never get close enough to the sun, since perihelion is farther than Neptune.<br /><br />Of course, Pluto's atmosphere is temporary. And comets have temporary atmospheres. Since Titan's atmosphere is evaporating, would you say it's also temporary?<br /><br />Temperature has an awful lot to do with this.<br /><br />As far as definition purposes goes, how thick would an atmosphere have to be? Our Moon has an atmosphere of argon. It is continuously generated by radioactive decay of potassium. When we reach the poles of the Moon, I wouldn't be particularly surprised if there's an enormous quantity of frozen argon there. The temperature's low enough. That might even be the factor that sets the Moon's atmospheric pressure.<br /><br />I have included moons in this discussion because at least two have atmospheres, and Enceladus appears to also have an atmosphere, although it might be temporary or transient.
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<font color="yellow">Which 4 objects are you referring to, and which Lagrange points?<br /><br />Pluto, Triton, 2003 UB313, and 2003 EL61; L4 and L5</font><br /><br />None of those objects are anywhere close to Sun/Neptune L4 or L5. As it turns out a bit of googling did turn up 4 objects at L4, although noone is going to mistake them for planets.<br /><br />See here: http://cfa-www.harvard.edu/iau/lists/NeptuneTrojans.html<br /><br />So far nothing has been spotted yet at L5.
No, I think they formed there. The points are not actually stable. Remember, Lagrange solved the <font color="yellow">three body problem<font color="white">. If you put massive objects in <font color="yellow">both <font color="white"> Lagrange points, it becomes the <font color="yellow">four body problem <font color="white">- and that's dynamically unstable.<br /><br />Another thing adding to instability is that anything flying past Neptune gains energy with respect to the Lagrange points. So they pump energy into the Lagrange points when they collide with the objects there.<br /><br />I think _all_ L4 and L5 points had large objects form there, including Lagrange points of the moons of the giant planets. And all these objects wound up escaping. Here is a picture of Miranda, I think the ovals are the crash sites of Lagrange objects:<br /><br />http://en.wikipedia.org/wiki/Image:Miranda.jpg<br /><br />The features are on the edges, about the two o'clock and eight o'clock positions.<br /><br />And Neptune's moon Proteus:<br /><br />http://en.wikipedia.org/wiki/Image
roteus_Voyager_2_%28big%29.jpg<br /><br />In this case, the Lagrange crash sites are at the 12:00 and 6:00 positions. I predicted finding these sites in advance of the Voyager flyby in a letter to JPL.<br /><br />Look around, there's a bunch of these!</font></font></font></font></font></font>
roteus_Voyager_2_%28big%29.jpg<br /><br />In this case, the Lagrange crash sites are at the 12:00 and 6:00 positions. I predicted finding these sites in advance of the Voyager flyby in a letter to JPL.<br /><br />Look around, there's a bunch of these!</font></font></font></font></font></font><font color="yellow"><br />In this case, the Lagrange crash sites are at the 12:00 and 6:00 positions. I predicted finding these sites in advance of the Voyager flyby in a letter to JPL. <br /></font><br />that's pretty freakin amazing, milkee-man. you get props <img src="/images/icons/wink.gif" />
I agree with the "mesoplanet" definition, although my personal preference was "minor planet" or "planetoid". Either way, I believe in a middle ground.
<blockquote><font class="small">In reply to:</font><hr /><p><i>bonzelite said</i><br /><br />Nobody is saying that anything and everything with moons is a planet. YES there are chunks of rocks with moons. but they are not planets.<br /><br />even if Pluto had no moons, this does not necessarily disqualify it from planethood. yes it is a KBO. ok fine. then we either decide that KBOs are for some reason "not" planets, or they are. i don't see the point in excluding KBOs from planet status just because they are farther away. what is the logic in that? especially when some of them are going to eventually be discovered that are the size of Titan, Ganymede, Mercury, etc.. i think Ganymede is actually larger than Mercury. but Mercury still stays a planet. let's demote Mercury then. some moons of Jupiter are bigger than it is.<br /><br />it's not necessarily size as it is physical traits. my opinion. does highly inclined or eccentric orbits disqualify planethood, then? is that the big deal? and if it is, then why? well, lets take a look at....<br /><br />...the REAL reason:<br /><br />i think the heart of the matter is really that the anti-planet people are threatened and insecure over the whole standard model of accretion --- /> that is the REAL issue --they don't want to admit that maybe the solar system did not follow this nice, safe, airtight little theory of accretion and nebular collapse so neatly and wonderfully. they do not have the answer. they do not have the knowledge. they do not win. they do not pass Go. they do not collect $200.<p><hr /></p></p></blockquote><br /><br />---------------------------<br /><br /><br />A valid point.<br /><br /><br />That oddly no one commented on...<br /><br />LOL<br /><br />
They better promote Ceres & co. to major planet status, too. Once they start discovering some of the really big KBOs out there, and call them minor planets, they`re gonna realize how pointless it is. <img src="/images/icons/smile.gif" /><br /><br />A minor planet is just as well an asteroid or a comet as a circular semi-planet. The definition just don`t fit both. <div class="Discussion_UserSignature"> </div>
<i>"They better promote Ceres & co. to major planet status, too. Once they start discovering some of the really big KBOs out there, and call them minor planets, they`re gonna realize how pointless it is."</i><br /><br />This argument is really all about <b>semantics, nomenclature and taxonomy!</b> It has nothing at all to do with theories of Solar System development or the how's and why's concerning the origins of these new-found celestial masses orbiting our Sun.<br /><br />Obviously, more stuff like this will be discovered in the future and in Science, all things <i>must be</i> systematically classified with similar units in a process called disambiguation. <br /><br />The International Astronomical Union (IAU), which is a member of the International Council of Science (ICSU), is responsible for maintaining a unified system of astronomical classification. Within the IAU is the Working Group for Planetary System Nomenclature (WGPSN) which maintains the astronomical naming conventions and planetary nomenclature for orbiting bodies. This is the seminal authority which will decide on a system to <i>disambiguate</i> the Solar System.<br /><br />Just like Ceres has been reclassified as a mere asteroid, rather than a major planet; it is <i>my opinion</i> that Pluto will also have to be redesignated as a Kuiper Belt Object to fit the new realities caused by recent discoveries!<br /><br />This isn't a bad thing. In the end it will help us get a clearer picture of the structure of the Solar System and in the future there may have to be several sub-classifications as new objects are discovered.<br /><br />The Kuiper Belt and Oort Cloud may someday have to be separated into several sub-sets such as inner and outer belts and/or areas far removed from the plane of the elliptic; to suggest a few examples. The same thing was done for the rings of Saturn when we discovered new ring divisions! <br /><br />It's just too cumbersome to call everything under the Sun a "Planet". I think n
<font color="yellow"><br />I think new names such as mesoplanet, planetesimal, microplanet, planetoid and the like, will have to become a part of the Solar Systems' lexicon and in the end it will help our scientific understanding of the universe. </font><br /><br /><br />i think it will help perpetuate status quo ideas that beg for revision.<br /><br />nobody cares about such hair-splitting. it is tedious and boring and entirely appealing to maybe a zoologist or a latin student or to the exclusive adoration of the scientific professional community. to the reader of Discover magazine or one who has coffee with the morning paper before going to punch a time card --they will be alienated. <br /><br />you call them planets. you do not skate over the fact that they are non-conforming to the ecliptic --you emphasize it. you say "Pluto is a planet that is very far away. it has 3 moons. it is in an area called the Kuiper Belt. it's orbit is highly different than most of the inner planets. this is because it formed in a slightly different way than the inner 8 planets. Planet Sedna, Xena, Santa, Quoaror, Abbot, Costello, Heckle, and Jeckle are also very cold and far away like Pluto." <br /><br />so on and so on, etc...<br /><br />it is a matter of time before they find more and more larger-than-Pluto objects, and probably a nearly Mars-sized KBO. and it will have a very weird orbit perhaps. and then what? you call it what? a chocolate cake-toid? <br /><br />the real issue is that nobody wants to admit that planetary accretion theory as it is currently known is WRONG. this is why they do not want to call these KBOs "planets." it would ruffle their egos and authoritative relevance. it would force them to confront their own myopic theory of equatorial zone core accretion and consider flushing it down the toilet. <br /><br />so instead we have this politically correct b.s. <br /><br /><br /><br /><br /><br />
<i>"I think it will help perpetuate status quo ideas that beg for revision."</i><br /><br />I agree! I think that's what science is all about; formulating ideas which naturally evolve as our knowledge grows! <br /><br /><i>"Nobody cares about such hair-splitting."</i><br /><br />Sure they do. Science is full of hair splitting...<br /><br /><i>"... it is tedious and boring and entirely appealing to maybe a zoologist or a latin student or to the exclusive adoration of the scientific professional community."</i><br /><br />I disagree; I think it's new and exciting! Your argument seems to be the same as saying; "Animals are animals, so why do we have to give them different names?". It aids in our understanding to classify things. Not only do we have lions and tigers and bears, but we have also have sub-sets; such as polar bears, Kodiac bears and Brown bears!<br /><br />Science needs to put things into a logical order <sup>1</sup>.<br /><br /><i>"You call them planets. you do not skate over the fact that they are non-conforming to the ecliptic --you emphasize it.</i> <br /><br />I agree; there will be <b>8</b> "Major" planets and other orbiting objects will be classified with an emphasis as to how they are non-conforming to the "Major" planets. <br /><br />But instead of calling them planets, wouldn't it be more logical to create a more defining term for them - to help emphasize how they are non-conforming? We call asteroids, "Asteroids", and that doesn't seem to be an issue. Why should KBOs and Oort Cloud objects be any different?<br /><br /><i>"...a chocolate cake-toid?"</i><br /><br />I don't think that name is properly descriptive and it would have to be Latinized into something like; <i>Cioccolatta Laganumtoid</i> to be internationally accepted and approved by the IAU.<br /><br /><i>"The real issue is that nobody wants to admit that planetary accretion theory as it is currently known is WRONG. this is why they do not want to call these KBOs "planets"."</i><br /><br />This is an issu
<i>mesoplanet is good. as long as they're all in that size range. </i><br /><br />How about Plutoiods in honor of Pluto and so we do not dishonor the little guy <img src="/images/icons/smile.gif" />. <div class="Discussion_UserSignature"> <p> </p><p><em><font size="1" color="#000080">Don't let who you are keep you from becoming who you want to be!</font></em></p> </div>
<font color="yellow">This argument is really all about semantics, nomenclature and taxonomy! It has nothing at all to do with theories of Solar System development or the how's and why's concerning the origins of these new-found celestial masses orbiting our Sun.</font><br /><br />So it be. Calling Mercury a planet while Pluto not, is arbitrary. If Mercury is a planet, then Pluto is it too. If Pluto is a planet, then Ceres is too.<br /><br /><font color="yellow">Just like Ceres has been reclassified as a mere asteroid, rather than a major planet; it is my opinion that Pluto will also have to be redesignated as a Kuiper Belt Object to fit the new realities caused by recent discoveries!</font><br /><br />Then you`ll havee to reclassify Jupiter and Saturn as gas giants, Uranus and Neptune as ice giants, and so on. <br />Pluto is a KBO, but that`s its sub-category. It`s a planet; as well as the terrestrial objects are planets.<br /><br /><font color="yellow">This isn't a bad thing.</font><br /><br />If Ceres had kept it`s status as a planet, it would probably have been visited by spacecrafts twice already.<br /><br /><font color="yellow">It's just too cumbersome to call everything under the Sun a "Planet". </font><br /><br />I agree with you on that; and that`s why we have terrestrial planets(Ceres would fit in under this definition), gas and ice giants; and why we should have KB Planets, and probably Oort Cloud Planets, too.<br /><br /><br />In my eyes, a planet:<br />- has enough mass to let its gravity make it roughly spherical in shape<br />-is no bigger than 13x the mass of Jupiter(it`s a brown dwarf/star above)<br />-does not orbit an object smaller than 13x the mass of Jupiter(then it orbit another planet, and is thus a moon)<br />- does not have to orbit another object(i.e. a star or a brown dwarf)<br /><br />This definition does not say anything about how the planet was created, or what sort of planet it is, but we got sub-categorys for that. <div class="Discussion_UserSignature"> </div>
A friend of mine had another idea: get ride of "planet" altogether. The word sounds like 'plane' and thus gives too much credence to the idiots in the Flat Earth Society. There is too much flat thinking on this planet already.<br /><br />His idea is thus: everything that is anything worth visiting is a ball:<br /><br />Fireballs: stars<br />Blackballs: black holes<br />Gasballs: brown dwarfs, jovians<br />Rockballs: terrestrial planets<br />Iceballs: ice moons, KBOs, Oort objects, and Pluto.<br /><br />Anything that isn't a ball is rubble, gravel, and dust.<br /><br />This classification system would have people thinking ballsy thoughts about space exploration, stamp out flat earth beliefs and planar thinking, and end the bad treatment of places like Ceres and Pluto. <br /><br />For objects that are a mix of two groups, for instance, brown dwarfs would be fiery gasballs, and moons like Ganymede and Callisto would be Icy Rockballs, and Titan, Earth, and Venus would be Gassy Rockballs.
Hm.... I quite like the word planet, and I <i>do</i> think of a 'ball' whenever I hear the word. And this is clearly discriminating toward the asteroids and comets! <br /><br />No... the word planet is more classy, methinks..<br /><br /><br />(Btw, I thought the FES was dead, since its leader is.) <div class="Discussion_UserSignature"> </div>
<font color="yellow">...disambiguation...<font color="white"><br /><br />Thanks for posting, harmonicaman. I agree with your post. That's a good keyword. You have helped me organize my thinking about this.<br /><br />I don't know why that word, "planet", seems to pull so much rank. To me, planets follow the Titius-Bode law. Althoug Ceres does that, it's just the tail end of a different class of objects than planets.<br /><br />The "classical" KBOs also have planet-like orbits that are fairly circular and follow (somewhat) the Titius-Bode law. But can we jam up the planet definition by including 2005 FY9, Quaoar, and several other objects in it? Now, THAT causes confusion!<br /><br />I would rather consider a class of objects, like asteroids, rather than have to memorize the names of a bunch of two-meter diameter rocks.</font></font>
Thanks <b>Mike;</b> I didn't mean to touch a nerve with people...<br /><br />I'm just attempting to present a logical argument for revising the Solar System's planet classification system which the IAU (International Astronomical Union) is currently grappling with. The IAU is a very conservative governing body and I am sure the decisions they render will be very thoroughly reviewed and acceptable to the scientific community and world at large.<br /><br />They may even decide to do nothing at this time, but because of all the new planetary discoveries, I believe changes will have to be made to put everything in its proper place in the Solar System.
dude, you've ordered too many kinds of latte's and coffees at Starbucks -- they're Planets. any other word is diminutive and marginalizing. people wake up to hearing "new Planet discovered." <br /><br />not "new mesoplanet discovered" --nobody cares. that does not make an impact like "planet." it just doesn't. period. a mouse is really "mus musculus." but nobody gives a rip's hind-end. it is "mouse."<br /><br />this is stupid ---- />"new ectoplanet discovered." c'mon, dude. that is so queer. it sounds like they found an egg yolk in space. <br /><br />they're Planets --in different regions, often with inclined and eccentric orbits. and they're turning up by the buttloads. and they rival Pluto in size. and they're round. the earth's moon is larger than Pluto. <br /><br />
puhhh-leeezz! let go and admit it's queer, dude. <br /><br />i tell you what, if the authorities who name planets decide on sub-latin planetoid stun gun phaser gun categories of KBOs, then i will write them all a letter telling them to go home. i'll boo them off the stage and throw rotten cabbage at them. <br /><br />
<b>Bonzelite -</b><br /><br />I thought you of all people would be excited about a new classification for all these new "Planetary" discoveries. <br /><br />Wouldn't a separate category for Trans-Neptunian planets highlight the apparent gaps in our understanding of the accretion disc theory of Solar System formation?<br /><br />I would think that a separate category of planets would help bolster your contention that accretion disc theory has fatal flaws!<br /><br />(Of course; I think the theory is basically sound and just requires a little tweaking here and there... <img src="/images/icons/rolleyes.gif" />)
i suggest they are all planets. and they are classified by region. i suggested this in some other thread a little while back. you can have the inner 8. then the KBO Planets - the K-Planets. then the Oort Cloud region - the O-Planets. this way, you know where they are and how they are classified as to their formation scenarios. <br /><br />yes, mesoplanet, ectoplanet, exoplanet, minor planet, planetoid, tyranosauraus planet --are all fine. they make sense, and that is why most posters suggest these. what i'm saying is that these designations lack relatability to most people --as cool as it sounds to you and i, nobody cares to decipher "mesoplanet." it is not evocative of anything relatable. even as a person keen to science jargon, i find it a bit silly. <br /><br />you say "astronomers discover 20th planet today" and you have a headline right away --creating enthusiasm and interest for nearly everyone. and it may be as large as Titan or Mercury. a Planet is majestic, mysterious, spherical -- a whole world. <br /><br />but i'm just repeating myself now --you say "2 new mesoplanets and one gastroplanet discovered last month" and you start confusing the picture and marginalizing some objects that may very well be as large as mercury or even mars --if you start to bury the planets in jargon, nobody will really relate to it. trust me. <br /><br /><br /><br /><br />
<blockquote><font class="small">In reply to:</font><hr /><p>tyranosauraus planet<p><hr /></p></p></blockquote><br /><br />"Tyrant Lizard" Planet? <br /><br />Anyways, in my opinion I believe anything smaller than the biggest moon in our Solar System, Ganymede, should be disqualified as a planet. This includes Pluto. <div class="Discussion_UserSignature"> </div>
<br /><br />Anyways, in my opinion I believe anything smaller than the biggest moon in our Solar System, Ganymede, should be disqualified as a planet. This includes Pluto. <div class="Discussion_UserSignature"> </div>why did you then start an entire other thread about this? <br /><img src="/images/icons/rolleyes.gif" /> <br /><br />t-rex is coming to get you for that.
<font color="yellow">Anyways, in my opinion I believe anything smaller than the biggest moon in our Solar System, Ganymede, should be disqualified as a planet. This includes Pluto. </font><br /><br />It "includes" Mercury as well. Doesn`t really matter as Mercury has never been my favourite planet. <img src="/images/icons/tongue.gif" /> <div class="Discussion_UserSignature"> </div>
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