Demote The IAU!!!!

jaxtraw · Aug 27, 2006

"There are plenty of other KBO objects of similar mass in the vicinity of Pluto. Even if they aren't right next to it, they are far closer in size, and orbit than for any other planet." I'm not disputing this. I'm simply asking somebody to justify why, from first principles, this should be a criterion for planethood. It has nothing for instance to do with the body itself- why does it make sense to define a planet purely in terms of its neighbours? Back with Jupier and Mercury- they really have nothing whatsoever in common. One is a very small rocky body, the other a vast agglomeration of gases, largely hydrogen. They don't share any traits at all. I wonder if intelligent beings had evolved on a Jovian moon, they'd probably relegate Mercury and the other terrestrials as unimportant "solar satellites" <img src="/images/icons/smile.gif" /> There are clearly two very, very distinct classes of planet- gas giants and terrestrials, so vastly different that "planet" can only loosely mean "body that orbits the Sun". I would add a third category- icy planets- the members of which more closely resemble the terrestrials than the terrestrials do the gas giants. It'd probably make more sense to have "gas planets" and "solid planets" with the latter subdivided into "rockies" and "icies". Astronomers are then free to define sub-groupings of them by composition, size, orbital characteristics, or any other useful categorisations. And I still think that the idea of "demotion" is inherently wrong. As Enceladus has shown, we really don't know which worlds are the interesting ones until we get a spacecraft or two there <img src="/images/icons/smile.gif" />

ittiz · Aug 27, 2006

I only have two major issues with the definition. One, orbital dominance makes a universe were a Jupiter sized object can be a dwarf and a Mimas sized object can be terrestrial in the same solar system! And two, the fact that dwarf planet doesn't mean planet, something that was done to make people who were uneasy about the number of planets happy. If you want to categorize objects in a belt as belt object no biggy, but if it looks like a planet it's a planet even if it's in a belt. It's just a belt planet. I think another thing which compelled them to boot Pluto is they didn't want to have to name more planets, they only had one name left and that was "Vulcan." I think they could have foregone that practice with the Pluto like planets. Maybe they could have used Roman emperors for the big Pluto like ones. Nobody would think they were crazy for having dozens or even hundreds of planets. Kids wouldn't have to learn about the small ones, that would be insane. Also the argument that Pluto is just like the other KBOs doesn't hold water. First off it's a sphere, secondly, unlike the lumpy KBOs, it has a crust, a mantle, and a core, which is like the other planets. If an planetoid is spherical it probably will have the internal layering of a planet. Just because it happens to be made out of the same stuff as the surrounding material doesn't mean that it's not a planet or the Earth would be a big asteroid.

Saiph · Aug 27, 2006

Meteor: that's the short version in straight english yes. But there are established precedents on how to identify each trait. For instance the "round shape" is based upon hydrostatic equilibriums, but the definition doesn't specifically site how to establish that. So, the wiki article shows how one would quantify "orbital dominance". And as the table shows, pluto isn't even close compared to the other planets in a very quantifiable sense. I mean, do you really see the IAU throwing all that into a press release? Or boiling it down to the general, fundamental idea for public consumption? Jax: Mercury and Jupiter do have some things in common. Their orbit a star, are round, and dictate the actions of bodies in nearby orbits. Part of the problem we have here is that Mercury through Saturn have been called planets for thousands of years, it's an entrenched definition. As such planet must be defined as such to include those planets into the group. It's the place of subgroups to further differentiate, such as terrestrial and jovian categories. If pluto was by itself, and it did dictate the actions of it's neighbors, I'd have no problem calling it a planet, but I would put it into another subcategory, as it's solid, but differs significantly in composition and structure from other terrestrial planets. Izzit: The only way you'll get Jupiter to be a "dwarf planet" and a smaller object to be a planet is in a proto-stellar system. I.e. it's still forming. In which case the planets would probably be classified as proto-planets. Also, we're finding other KBO's that rival pluto in size, not just composition. <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>

MeteorWayne · Aug 27, 2006

Saiph: I mean, do you really see the IAU throwing all that into a press release? Or boiling it down to the general, fundamental idea for public consumption? Unfortunately, that is my point. This was not a press release, it was the actual resolution that was passed. Is there an IAU definition of "orbital dominance"? We all know what it means, but the resolution does not even use that term. Like I say, I'm in the 8 planet camp, since to me Pluto is but one of (but not) the largest objects in a large population (Plutinos) It's a minor or dwarf planet. But the "clearing out" is a poor choice of language for what we are trying to say. <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>

ittiz · Aug 27, 2006

Well you could have several Jupiter mass planets with slightly elliptical, inclined orbits that cross each other relative to the orbital plane like Pluto. Then a cleared out area between where the planets reside and the star where one Mimas sized world resides. It may be unlikely (although possible not), but I'm sure there all solar systems with configurations like that out there. Also the KBOs that are large like Pluto shouldn't be KBOs because they are built like planets. Unless the object is a solid peice of iron or some such material there is no way it wouldn't be like a planet and still be the size of Pluto.

MeteorWayne · Aug 27, 2006

Please note. The definition refers only to only "the SOLAR System" and not any other stellar system. Maybe a more universal definition would have been better, but we don't have a large (and deep) enough tally of what other stellar systems have to evn try. I think the public was demanding an answer, and the IAU, while trying to do the right thing, went too far too fast. At least that's what I think right now as I digest what we all have written today. <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>

Saiph · Aug 27, 2006

I don't think having multiple jupiter sized planets on intersecting orbits is a stable system. <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>

jaxtraw · Aug 27, 2006

I don't see anything about stability in the IAU definition either <img src="/images/icons/wink.gif" />

Saiph · Aug 27, 2006

it isn't, however such a system will quickly (in astronomical terms) change to a simpler, more stable system. I.e. it won't stay that way long, and you'll get a planet (probably larger than before) that dominates the area. <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>

vidar · Aug 28, 2006

Take up the cry!!! Demote The IAU!!!! I'm mad as hell and I'm not going to take it anymore!!! Give Me Nine Planets Or Give Me Death!!! Harumph!!!! -------------------------------------------- I think it is bad politics to demand demotion of an assembly when a vote is lost. If a ‘right’ point of view was not decisive on the decision, one should really try to gain support to the view in time rather than demand demotion of the assembly. What are the motives for that anyway? I think there is an increasing need for classifications of the planets as increasingly more are discovered in our space. Now that the ancient and useless definition is about to be specified, it opens up for classifications that fits our present perceptions. I think more classifications will be resolved in the nearby future. The definition of Dwarf, Terrestrial and Jovian planets might even be revised.

vidar · Aug 28, 2006

MeteorWayne Isn’t our moon a dwarf planet? It seems that the two obstacles are whether it circles the sun and whether it’s not a satellite. In a way, our Moon circles the sun, rather than Earth. http://en.wikipedia.org/wiki/The_Moon%27s_orbit#The_Earth_.26_Moon.27s_path_around_the_Sun What is the upper size for a natural satellite anyway, isn’t it the lower size of a Dwarf planet? If so, the Earth and the Moon can be a Terrestrial and Dwarf double planet system. To me they are. It would be very interesting to know which of the following has a concave orbit towards the sun. http://www.solarviews.com/browse/misc/plntmoon.jpg Titania is to small to be a dwarf planet anyway, but Pluto, Mercury and our Moon have concave orbits around the sun. what about Ganymede, Titan, Callisto, Io, Europa and Triton?

cuddlyrocket · Aug 28, 2006

The Moon is not a dwarf planet because it is considered a satellite of Earth. ('Satellite' is not precisely defined, but I can't see any definition being accepted that would result in the Moon not being a satellite of the Earth.) There is no upper size limit for a natural satellite. Some of them - Ganymede for instance - have greater diameters (although not greater mass) than Mercury. 'Terrestrial and Dwarf double planet system' is a contradiction in terms, as a dwarf planet is not a planet. You could possibly have a 'terrestrial planet and dwarf planet double system'.

vidar · Aug 28, 2006

CuddlyRocket A planet is a satelite to the Sun. The Moon circles Sun rather than the Earth. They are in (almost) the same orbit around the sun. http://en.wikipedia.org/wiki/Natural_satellite A natural satellite is a non-man-made object that orbits a planet or other body larger than itself. It is commonly referred to as a moon (not capitalized). The term natural satellite may also refer to a planet orbiting a star, as is the case with planets orbiting the Sun.

alokmohan · Aug 28, 2006

"A planet is a satelite to the Sun. The Moon circles Sun rather than the Earth". They are in (almost) the same orbit around the sun. I am sorry to say you are absolutely wrong.A planet is not satellite to sun.

ittiz · Aug 28, 2006

Our moon could be considered a dwarf moon but not a planet. It is well within earth's hill sphere. Also, the way I see it you can't have a terrestrial dwarf double planet. A terrestrial terrestrial double planet yes, but I think if one body falls into a smaller class that it should be considered the moon. That also fixes all the crud that arose with the last moon definition proposal. If what orbit a moon has doesn't matter and it only depends on which class it's in then you don't have planets magically becoming moons and visa versa.

serak_the_preparer · Aug 28, 2006

I think it is bad politics to demand demotion of an assembly when a vote is lost. And there you have it. Politics. This recent exercise was as political as it was scientific. The definition was drafted in such a way that Pluto and Pluto-like worlds would be 'out,' while the other planets would be 'in.' (Not that there's necessarily anything wrong with the definition produced by this process.) Some astronomers wanted Pluto's planet status stripped, toiled hard for that end, and got what they wanted. If the concern was that too many newcomers would be allowed into the planet club, there was a simple enough solution: a new definition with a grandfather clause. Pluto would therefore be 'grandfathered in' by virtue of having been awarded planet status before the new definition took effect. All subsequent planet discoveries would take the new planet test on a pass/fail basis. This would basically acknowledge the force of history, as well as the cultural signifigance of the appearance of the 9th planet three-quarters of a century ago. As well, neither Neptune nor Mercury would be threatened by any revised definitions, now or in the future. The current heirarchy of the solar system would be locked in place, with small chance of anyone new showing up to crash the party. 'Force of history'? 'Cultural signifigance'? What's any of that got to do with science? Even astronomy has a special history, and a culture, and a relationship with the larger history of ideas and scientific-technological culture in which it has grown. Also true, by the way, for every other branch of science. The IAU declaration could have read something like: Henceforth, all new discoveries considered eligible for planetary status must meet the following criteria, subject to review by the next IAU conference held after the discovery. The stipulated criteria are... Yes, yes, I know. Terribly unrealistic of me.

MeteorWayne · Aug 28, 2006

Even though I am in the other camp, there's a lot to be said for your idea. Wayne <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>

Saiph · Aug 28, 2006

except there should be no "force of history" exerted upon a scientific classification scheme. If so, we'd be stuck with linear progressions for the tree of life, instead of the branching system we have now. People argue that science is too rigid, that it sticks to precedent rather than adapting to new evidence. Now that science is considering (well officially deciding) to take new observations into account, the entire other half of the crowd is screaming blood murder. This gets the ball rolling. An official resolution was passed, many people don't like it. My guess is that enough astronomers will be throwing this around to reconsider the entire proposal at the next IAU meeting. <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>

MeteorWayne · Aug 28, 2006

Saiph: "This gets the ball rolling. An official resolution was passed, many people don't like it. My guess is that enough astronomers will be throwing this around to reconsider the entire proposal at the next IAU meeting. " I agree. At least we have something concrete (or at least semi solid <img src="/images/icons/smile.gif" /> ) to argue about. <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>

Saiph · Aug 28, 2006

right, the one thing people really should remember is that before this, there was NO definition for a planet. <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>

vidar · Aug 29, 2006

Alokmohan I am sorry too, the satellite criteria is confusing. It’s Wikipedia that says: A natural satellite is a non-man-made object that orbits a planet or other body larger than itself. It is commonly referred to as a moon (not capitalized). The term natural satellite may also refer to a planet orbiting a star, as is the case with planets orbiting the Sun. http://en.wikipedia.org/wiki/Natural_satellite (If so, isn’t our Sun a satellite to the superstar in the centre of our galaxy?) My point is that the definition of a dwarf planet should be specific of what it can’t be a satellite to; a Dwarf-, a Terrestrial-, a Jovian- planet. Can’t a dwarf planet be caught up in an orbit around a Jovian planet like Jupiter? If, I think the dwarf planet has become a natural satellite to Jupiter as well.

vidar · Aug 29, 2006

Ittiz This second drawing shows our Moon’s orbit around our Sun. http://www.math.nus.edu.sg/aslaksen/teaching/convex.html It’s wikipedia that says: The Moon is attracted towards the Sun more (about twice as much) than it is towards the Earth, and the combined Sun-Earth "pull" that determines the path of the Moon is always directed inwards, towards the Sun. http://en.wikipedia.org/wiki/The_Moon%27s_orbit#The_Earth_.26_Moon.27s_path_around_the_Sun Most stellar objects are pulled by more than one object. In fact the Earth is pulled by the Moon as well. But all in all, both the Earth and the Moon are satellites to the Sun. That makes the Moon-Earth a double planet system.

derekmcd · Aug 29, 2006

That makes the Moon-Earth a double planet system. I believe one of the main stipulations for a binary planet system is that the barycenter (center of mass) is not within either one. The barycenter of the Earth/Moon system is inside the Earth. Pluto and Charon, OTOH orbit about a barycenter in between the two bodies... and thus have been considered a binary system. <div class="Discussion_UserSignature"> <div> </div> <div>"If something's hard to do, then it's not worth doing." - Homer Simpson</div> </div>

vidar · Aug 29, 2006

derekmcd It’s true that the Earht/Moon barycentre is inside the Earth. But the barycenter is not part of the dwarf planet definition. However, the dominant object to the Moon is the Sun, not the Earth.

derekmcd · Aug 29, 2006

<blockquote>In reply to:<hr />However, the dominant object to the Moon is the Sun, not the Earth. <hr /></blockquote> I think using this as a standard would provide confusing results. Take a very large/very small 2 body system and place it close enough to the sun, it is a binary system. Take 2 objects the nearly the same size and place it far enough away from the sun and and it is a planet/moon system. That doesn't make sense... at least, to me it doesn't. <div class="Discussion_UserSignature"> <div> </div> <div>"If something's hard to do, then it's not worth doing." - Homer Simpson</div> </div>

Demote The IAU!!!!

jaxtraw

Guest

ittiz

Guest

Saiph

Guest

MeteorWayne

Guest

ittiz

Guest

MeteorWayne

Guest

Saiph

Guest

jaxtraw

Guest

Saiph

Guest

vidar

Guest

vidar

Guest

cuddlyrocket

Guest

vidar

Guest

alokmohan

Guest

ittiz

Guest

serak_the_preparer

Guest

MeteorWayne

Guest

Saiph

Guest

MeteorWayne

Guest

Saiph

Guest

vidar

Guest

vidar

Guest

derekmcd

Guest

vidar

Guest

derekmcd

Guest

Similar threads

TRENDING THREADS

Latest posts

Share this page