More likely, the definition of planet will be refined to contain the criterion that "it has cleared its neighborhood of planetesimals", allowing the classification of only 8 bodies in our Solar System as planets to remain.
I think that's going to be difficult. Too many of the minor planets are far enough away that there is no possibility of determining what debris is in the vicinity of their orbits. To me, if it's big enough to have become round due to gravity and it isn't a moon, then it's a planet. And, if the definition of "moon" isn't good enough, they'll have to fix that, too.
which is precisely why they will not meet the criterion, as it cannot be shown that they have cleared their neighborhood of planetesimals. I don't have any real logical objection to your definition, save for the fact that , in the context of science education (which, really, is the only context of this battle over nomenclature for Pluto), it is even worse than only having 8 planets... as there will be hundreds and maybe, eventually, thousands of planets. that's hard to romanticize.
Well, it's hard to romanticize in the way we're used to - I'll certainly grant that. I agree that science education is a serious aspect of this naming thing. I don't believe we'll find all that many new planets that are massive enough to have become spheres. So, I'm not to worried about the large numbers issue. BUT, when I talk to kids about the sky I WANT there to be questions that are obvious, clear and NOT answered. Why would any kid get more excited about memorizing some fixed number of planets than about the possibility of finding new stuff and discovering more completely how our solar system works? Pluto got discovered in 1930 by a young researcher working for an observatory. He took photographs if the sky and looked for objects that moved! I think that's cool. In most cases, asteroids get found by private individuals looking at the sky using similar techniques - not NASA. I think the possibility is what's interesting.
Because one precedes the other. They are not mutually exclusive, but rather chronologically ordered proposals. You aren't going tobget kids to care at all, without some sort of shiny bauble to get them interested in the first place. At least, I feel this is at the root of the objections.
I agree. I'll have to tell you that I get more mileage out of presenting what we don't know - the possibility. The list of facts isn't a shiny bauble as far as I can detect.
Pluto to be Re Planetized. Our Science $ at Work. It's confusing to subdivide planetary objects in our own Solar System into finer & finer categories, just at the time we're first discovering exo-planets around most other stars. How can we categorize them into the fine grained descriptors we use to admit or reject planetary bodies into groups here around our Sun? We can't. Furthermore, it's presumptive to assume those same categories will exist around other stars. I vote we return to a simpler, time honored system, where a planet is any astronomical body that is: 1. not a star; 2. orbits a star; & 3. is massive enough to assume a spherical shape. Once recognized & accepted as a "planet," then it could be subdivided into a wider variety of objects, like protoplanets, rocky planets, dwarf planets, gaseous planets, etc--or others.
I like your 3 criteria. Isn't that the direction being proposed - the change that would again categorize Pluto as a planet? It would be outstanding to be capable of detecting Pluto sized exoplanets!!
I believe not only Pluto should be classified as a "planet," but every other body in the Solar System that meets the three criteria. I don't understand why someone in a position of authority decided we should limit our Solar System to an arbitrary maximum of 8 planets--especially when we're now discovering other planetary systems that have more. In truth, most stars probably have dozens of planets. Why shouldn't we enjoy the fact that we do too? I agree with you that it would be wonderful to develop the instrumentation capable of seeing Pluto sized planets around other stars. Perhaps we could create systems that could actually see details on Earth-sized planets to determine the possibility of life there? It's nice to dream.
Most of this arises from a desire to keep young people interested. Ever try to make a solar system mobile with 58 planets? I bet it isn't easy...
Speaking for myself personally, I feel that being scientifically accurate is more important than dumbing down our planetary system to encourage our youth to be interested. I'm confidant they'll be interested anyway. And to me, a Solar System with "58" planets is far more interesting than one with only 8. I have no fear, no apprehension and no hesitation in adding Pluto, Eris, Sedna, Ceres, and every other new-found world out there that qualifies as a planet, to our growing list of family members. Indeed, I find it thrilling!
Well, there are objects orbiting the sun in the size range of Jupiter on down to dust. Besides planets and dwarf planets, the Kuiper belt and Oort cloud of stuff orbit the sun, too. There are asteroids and comets of various origins orbiting the sun as well. I don't see any evidence that the rule that made Pluto (and various other objects) dwarf planets was created in order to dumb anything down. If the new rule set is accepted, Pluto will be considered a planet, not a dwarf planet. And, so will Ceres, Charon and 2003 UB313 - 12 planets. And, Eris, Makemake, and Haumea will be the dwarf planets currently known, I think. Is that some big improvement in describing our solar system to the public? I really doubt it. It's certainly hard to argue that it is more scientifically accurate.
While I appreciate your opinion, you are not a child. Furthermore, your characterization as "dumbing it down" is not accurate or appropriate. Also, the "58" number was arbitratry. If we make pluto a planet, then that "58" number will likely and eventually be a 4-digit number.
For some reason, people can’t wrap their minds around what science is. Everyone wants a susinct and simple answer to all questions when, in reality, it’s always an ongoing modification of what has come before as new evidence becomes available.
Interesting thoughts. . .though personally, I feel it's best to simply go to the simplest, easiest, and most accurate system of regarding everything 1. not a star; 2. orbiting a star; 3. massive enough to retain a sperical shape, and 4. not a comet. . .as a planet. That would include everything in the Kuiper Belt & the Oort Cloud that fulfills the requirements mentioned, as a planet. That fits better in a system that is increasingly including new findings on exo-planets around other stars. We need a system that deals with Solar & stellar planets smoothly and without glitches. The intermediary step you mention could work, I suppose, for awhile. But why go thru two change steps and disrupt everything & everyone twice, when one complete step could accomplish it all with less overall stress?
I was simply responding to YOUR post, as you worded it. Whether the total number eventually becomes "58" or 1,258, makes no difference. It's easy to say, "We have 1,258 planets in our Solar System, but we'll limit our discussion to those known to Man from ancient times thru the twentieth century," or something similar. We have to devise a system that is compatible with our own Solar System objects plus the ever increasing new discoveries coming in constantly for exo-planets. We can't have one system for studying our local planets and a different system for studying planetary systems beyond the Sun. That's all I'm saying.
To an educator or their child student? Oh, I think it does. And...if it "makes no difference"...then why are you resisting? This is precisely what the planet/minor planet classification attempts to do! I don't disagree, really. The physical is no different. It's just an example of the scientific community trying bring science to laypeople,and especially kids.
The rule that made Pluto a dwarf planet DID have a purpose. You keep saying "most accurate" or whatever, but there is no issue of accuracy. With the current change, it is just as accurate. It's just that there won't be a name specific to planets that have cleared their orbits. Frankly, I just don't see any reason for celebrating that.
Seems to me the 'simplest' method is if it orbits a star it is a planet and if it orbits a planet it is a moon...no matter it's shape. However, there must be a minimum size definition to extract the debris and dust, etc. We can't judge by solid versus gas, or with or without magnetic field, or gravity, etc. If a comet is large enough, and orbits only a single star, then it's a planet. But first the question should be 'what is the purpose' of naming objects a planet?
Regarding your "minimum size" question, if its mass is so small that the object is not spherical in shape, then categories like asteroids, planetoids, meteors, comets, etc, can be applied. I hadn't thought about including spherical comets as new "planets," but that's an interesting possibility. I'm not sure how the astronomical world would react to that though.
The new and current designation of "Dwarf Planet" makes perfect sense and eliminates the nightmare of hundreds of planets while maintaining the designation of the other couple hundred thousand solar system objects. If it is spherical and orbits the sun while clearing out everything in its path its a planet. If not it is not.
The thing that bothers me about the definition you cite is the part about "clear its (orbital) path". Some exo-planets we've recently discovered are attached to new-born stars, and are still in the process of forming themselves. They are 1. not stars themselves; 2. orbiting the star itself; 3. they're massive enough to maintain a spherical shape. But they haven't yet cleared their orbital path of debris around that star. So, does that make them ineligible to be called "planets"? I don't think so. They're proto-planets, but they're still planets. Creating excessive groupings or designations to label and package every known entity in the universe, simply creates more confusion and becomes more burdensome to learn & use. The best way is to simplify, simplify, simplify. The general term planets should cover them all, regardless of their individual differences.
Over simplification leads to inaccuracies. The more information we have, the greater the need to be organized by groups. Wether it’s astonomy or biology, as more evidence is acquired, the greater the need for accuracy. If you extend this over simplification idea to biology for example, we’d had two kingdoms, the plant and animal, with no phylum, class, order, species etc.
I'm not advocating being simplistic, or being insensitive to the various differences that need to be addressed. I'm simply saying the word "planet" should be kept more generalized and less specific than we have now. You can add all the sub-classes of planets you wish to account for the wide differences out there, but proto-planets, gas planets, rock planets, dwarf planets, gas giants, etc, are all important distinctions, but they should all be categorized under the general title, "Planet." That's all I'm saying.
