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Unmanned Spaceflight.com _ Pluto / KBO _ "Pluto is dead" - Mike Brown
Posted by: SigurRosFan Aug 24 2006, 01:58 PM
- http://www.space.com/scienceastronomy/060824_planet_definition.html
- http://news.bbc.co.uk/1/hi/world/5282440.stm
Posted by: ugordan Aug 24 2006, 02:05 PM
Quick! Is there still time to redirect New Horizons to say... Uranus or Neptune? 
Sorry, I couldn't resist...
Posted by: SigurRosFan Aug 24 2006, 02:15 PM
What's Alan's email address? 
Posted by: djellison Aug 24 2006, 02:31 PM
Why would this affect NH in any way, shape or form.
Pluto is still Pluto. Still fascinating, still unexplored, still part of a collection of bodies that we need to learn about.
The silly thing about this entire episode is that it's making the news......but no one has learnt anything, no one has discovered anything, nothing has changed.
Doug
Posted by: Ames Aug 24 2006, 02:41 PM
Doug
Oh I don't know about that. As the saying goes “There’s no such thing as bad press”
The public has learnt that that the Solar-system is a much more varied and interesting place than that taught to them in school (25 years ago in may case
) and highlighted the problematic discoveries of large bodies that don’t conform to the old rules.I think it's fascinating, and I think the correct decision has been made.
I am also glad that NH is on it’s way (Phew!)
Nick
Posted by: Paolo Aug 24 2006, 02:43 PM
I am quite happy of the decision because
1) the definition of planet that was approved is exactely the same I have been promoting for some time
2) New Horizons is already launched. I wonder how more difficult it would have been to "sell" the mission had Pluto already been demoted
Posted by: Rob Pinnegar Aug 24 2006, 02:44 PM
...Which makes it perfectly suited for making the news.
And yes, we *are* lucky that New Horizons is already launched. It's hard to see how Pluto's demotion from planetary status could have failed to affect the mission, had this happened a few years ago.
Posted by: ugordan Aug 24 2006, 02:45 PM
It shouldn't. I was joking -- hence the smiley.
Although I am one of those "demote Pluto" guys, I still think Pluto is a worthy target to explore. I'm eagerly awaiting July 2015 as much as the next guy. Just as I'm looking forward to Dawn visiting Ceres and Vesta. To me it makes very little difference what the object's classified. As long as it's interesting, I wanna see it explored.
That's why this whole thing is silly and absurd as you say; I was just trying to lighten things up a bit
Posted by: David Aug 24 2006, 02:49 PM
Just wait until Senator Curmudgeon (C-New Dorkshire) stands up in Congress and demands that New Horizons be "recalled" because "the people of this great nation don't want to see their tax dollars wasted sending machines to 'dwarf planets'!"
Posted by: Myran Aug 24 2006, 03:26 PM
We discussed this earlier, and this triggered a conversation with one friend with a nice astronomical interest some time later (He's not a full fledged space buff, but well infomed).
And his view was already then that Pluto should be demoted for the simple reason that Pluto cross the orbit of Neptune.
As for me I kept the view that Pluto should remain a planet for 'historical reasons' even though my hesitation had grown somewhat. I think I had a problem of demoting a planet since I have grown up with the idea that Pluto are one planet.
Now the verdict are in, I live with it. Pluto are still there, whatever it is called. Yet like some already have hinted, it might have been hard to get a mission underway if Pluto was not seen as part of the planetary family. So its the best of both worlds..... Pluto and Charon thats it!
Posted by: JRehling Aug 24 2006, 03:30 PM
And yes, we *are* lucky that New Horizons is already launched. It's hard to see how Pluto's demotion from planetary status could have failed to affect the mission, had this happened a few years ago.
I disagree. It was a long, slow fight to get a Pluto mission, and I don't think anyone involved would want to have any extra ammunition whatsoever in the hands of the political opponents of it.
I could see someone in a House committee saying, "The damn thing's not even a planet any more," getting a round of laughs, and a representative or two thinking that the same line would seem persuasive to a few voters or fundraisers, etc. Or Goldin pushing the same line. I don't see the impetus towards the mission having been so solid that it might not have been derailed by an additional flyspeck of resistance.
NH has 9 years to go. I would be very surprised if this issue remains settled. Anticipation of NH's arrival itself might spur reconsideration of the issue. It's credible that NH's observations might rekindle the issue if Pluto is found to be particularly lively.
If the scads of rival definitions has made anything clear, it's that "planet" is a category with many properties that one person or another finds to be relevant in its conceptualization. Most of the reasoning that has gone into the debate has involved appeals to intuitions: Gut-level reactions to hypothetical cases have been used repeatedly as the test of a definition. If this tells us anything, it should be that the gut-level reaction is the real definition of "planet", and we're just trying to reverse-engineer it into a codification. We all know that Saturn and Mars are planets, and we pretty much all "know" that Charon isn't. When we get a definition that counters what we "know", we reject it. Again, what we already "know" *is* the definition of planet, and there's no guarantee that it codifies elegantly. As the Supreme Court justice said of pornography vs. art, you know it when you see it. Of course, different people have different opinions. That, to me, is the end of the line. The embarrassment and the indecision shows that it was a damaging exercise that missed an opportunity to do the right thing and NOT define the undefinable. And this issue is not settled, I promise.
Posted by: centsworth_II Aug 24 2006, 03:37 PM
Discovery also includes better understanding what you already "know". This discussion could be a good way of letting the general public see some of the behind the scenes workings of science. Like a tour through a slaughterhouse to show the messy reality behind the neatly wrapped meats in the grocery store, this shows the messy reality behind the neatly wrapped scientific "facts" in school books.
Posted by: RNeuhaus Aug 24 2006, 03:42 PM
And now what astro category belong to Pluton? Icy Asteroid?
P.D.
Never mind. I have already read others pages: --> Dwarf planet. It does not sound me good! because its nomination is the same: Planet.
Rodolfo
Posted by: djellison Aug 24 2006, 03:45 PM
This isn't science though. We have not measured the composition of anything, nor have we found something new. We've not measured an albedo, taken a spectra, imaged an occultation......it's just administration.
And to be honest, given that 2 weeks ago we had 9 planets, 1 week ago we had 12 or more, and now we have only 8.....it's made the scientists involved looked more than a little silly.
Doug
Posted by: punkboi Aug 24 2006, 03:46 PM
Look on the bright side, with only 8 planets now... Our exploration of the solar system is officially complete! USA! USA! USA! Just kidding.
Posted by: um3k Aug 24 2006, 03:53 PM
No, no, it's not complete until all the planets have had orbiters!
Posted by: volcanopele Aug 24 2006, 03:55 PM
grrr.... needless to say I am very unhappy right now. I'll live, but still 
I'll see if www.demoteearth.com is still available.
Posted by: JRehling Aug 24 2006, 03:56 PM
And to be honest, given that 2 weeks ago we had 9 planets, 1 week ago we had 12 or more, and now we have only 8.....it's made the scientists involved looked more than a little silly.
Doug
I completely agree.
Several years ago, I stated the opinion that it is a mistake to think that doing science is hard but naming things and defining categories is easy. In this case, none of the "science" is particularly sophisticated: You could teach an intelligent person with no science background all of the relevant science in at most a few hours. This is very different from the debates around biological taxonomy, which pertain to encyclopedic arcana.
I would have put this issue to professional categorists, cognitive scientists to wit, instead of professional astronomers.
In a business, you learn that professionals in area X really are better at it than smart people who are dabbling in area X. A smart engineer should not take over a sales job. A smart marketer should not install computer hardware. I think what we've seen here is that being smart at astronomy doesn't make someone a good categorist. I think if the "facts" and position-papers supporting three to ten rival definitions had been handed to people who study categorization, they could have rendered an elegant embarassment-free definition that the scientists themselves could not. They were basically operating in an area outside their expertise: Astronomy has had an easy time of it, distinguishing between white dwarfs and neutron stars, neutron stars and black holes: distinctions that are sharp and clear. The first outing in a really tough categorization task has shown the lack of experience.
Posted by: centsworth_II Aug 24 2006, 04:05 PM
I read that Pluto was the only planet discovered by an American.
Posted by: centsworth_II Aug 24 2006, 04:16 PM
This whole discussion has opened up precisely because of how many new things have been discovered about the solar system. Science is not just the collecting of data, it is also putting the data in context with what is already known.
Like the classification system of living things has changed with new genetic studies, the classification of solar system objects must change with new discoveries. In neither case will the changes be quick, easy, static or uncontroversial. But in both cases, the classification discussions are very much part of the science.
Posted by: Toma B Aug 24 2006, 04:18 PM
Well, I'm personaly not very happy about losing Pluto as planet but at least I can say that I have saw all 8 planets with my 4,5" telescope...
I'm just guesing what size asteroid (or whatever) has to be to be planet...because when Pluto was discovered it was thought it is 6000 km in diameter, and that would be a planet!
Posted by: David Aug 24 2006, 04:24 PM
And now I have to update http://www.unmannedspaceflight.com/index.php?s=&showtopic=2160&view=findpost&p=50516:
As for Pluto, Sir or Madam,
Fame and glory, it has had 'em
But it's gone the way of Adam --
Wasn't good enough for me!
Gimme that Old Time Solar System
Gimme that Old Time Solar System
Ceres, Pluto -- never missed 'em
They're not good enough for me!
Posted by: djellison Aug 24 2006, 04:24 PM
B)-->
No it wouldn't.....it's neighbourhood would not be cleared so it wouldn't be a planet.
Unfortuantely, the same is true of almost every 'planet' in our solar system...so this definition has written of most of the planets we have. I'm unsure of how many Venus and Mercury crossing asteroids there are...but at the moment I think we've got about 3 planets by this definition.
Doug
Posted by: JRehling Aug 24 2006, 04:26 PM
B)-->
Well, I'm personaly not very happy about losing Pluto as planet but at least I can say that I have saw all 8 planets with my 4,5" telescope...
[/quote]
Yeah! I will add that I saw all of them in one night, and I made the observations of increasing distance from the Sun, with the Moon inserted into the sequence. Had to stay up mighty late to do it.
Posted by: RedSky Aug 24 2006, 05:04 PM
Yep... Clyde Tombaugh discovered it in 1930 from Arizona. Throughout the 1920's, there had been a lot of hype in the U.S. public print media about "the search for Planet X". It was suspected because of supposed perturbations seen in Neptune's orbit that another outer planet should exist. Clyde knew after the discovery that it could not have been the Planet X they were looking for... it was too small to be responsible for the Neptune perturbations. (which later observations resolved away any large discrepancies in Neptune's orbit, so in fact, they were searching in vain).
Actually, the only people with any justifiable emotional connection with Pluto and its status should probably be Percival Lowell (of the infamous "canals on Mars" ordeal), Clyde Tombaugh, and perhaps, Walt Disney
... and I doubt right now that they care. The true person who pushed for the search was Percival Lowell, who employed Clyde at his observatory near Flagstaff, AZ for the main purpose of searching for "Planet X". If there hadn't been all the hoopla of "looking for Planet X" and the "name the new planet" hype afterward... the 1930 discovery would probably have been barely noticed except for a mention of "asteriod found on the edge of the solar system in highly inclined orbit". But, as it was, with all the hype, Percival Lowell got his claim to fame... since the selection of the winning name of Pluto officially has as its symbol an overlapping "PL"... his initials!
Posted by: David Aug 24 2006, 05:12 PM
I don't believe that's at all true. In the context of 1920s astronomy, minor planets (asteroids) were defined by their position inside Jupiter's orbit. There was no term other than "planet" available to describe Pluto at the time, as it certainly was not a comet or a meteor. Pluto was also initially (and for several decades) imagined to be at least the size of Earth. Someone who described Pluto as an "asteroid" in 1930 would have looked ridiculous. Regardless of the inclination of its orbit (which is, for most people, a pretty esoteric detail), any object beyond Neptune that was bright enough to be detected in 1930 would have been dubbed a planet.
The importance of the "Planet X" search has nothing to do with "hype", but rather the fact that without the Planet X search Pluto would not have been discovered at all in 1930, and probably not for another six decades.
Posted by: JamesFox Aug 24 2006, 05:16 PM
Well, I don't really minf the intent to divide things into the 8 regular planets, dwarf planets, and all others, but I think the given definition is screwey. They should have used the vague, but more appropriate term 'orbital dominance'.
Posted by: odave Aug 24 2006, 05:20 PM
...and I'm relieved that I don't have to try for "Xena" now - can't afford that kind of equipment!
Posted by: punkboi Aug 24 2006, 05:50 PM
All I can say is... The http://pluto.jhuapl.edu will have a couple of revising to do...
Posted by: Paolo Aug 24 2006, 06:05 PM
Speaking of which, the Italian television has just aired a news story about Ceres' discoverer Piazzi and his small town of birth some 100 km from here (Milan)
Posted by: Holder of the Two Leashes Aug 24 2006, 06:23 PM
Like JRehling, I predict that shortly after July 2015, at the latest, we will be posting a "Pluto is resurected" thread here.
Posted by: ElkGroveDan Aug 24 2006, 06:47 PM
I predict that popular culture will continue to speak of "the nine planets" and the "planet Pluto". As someone said on a previous topic, the whole concept of the nature of a planet has been largely cultural and linguistic one anyway.
My experience is that "official" attempts to dictate changes in time-honored concepts and traditions often fall flat (outside of totalitarian dictatorships, that is). I recall that in the 1970s "everyone" was of the view that the US should switch to the metric system. President Carter even went so far as to issue executive orders dictating the use of metric measurements in all things related to the US government. The transition began, but it never stuck. I used to have a 1980 Oldsmobile that required two sets of socket wrenches, metric for the body and English for the engine.
The point is that the movement never stuck in US culture and eventually everything reverted back to our English standard (with no commentary from this former engineer as to which system is "better.") I believe the same will happen with this decision on "the Planets." Lacking any kind of "enforcement" school teachers will keep their expensive models and collections of elementary textbooks. This news will fade in about three days, and a month from now the average disinterested members of the public will forget that it ever happened.
Posted by: djellison Aug 24 2006, 06:57 PM
I know I will.
That - or accept a set of definitions that technically remove planetary status from just about every planet in the solar system.
Doug
Posted by: David Aug 24 2006, 06:58 PM
Yes, but there are always going to be officious up-to-date people who will undertake to "correct" them if they happen to speak of "nine planets". The worst are going to be the smart-alec kids who will raise their hands in 4th grade and say, "Excuse me, Miss Barringer, but astronomers now say there are only eight planets." You know, kids like you and me when we were that age.
Posted by: JRehling Aug 24 2006, 07:01 PM
This is why I thought the "biggest" thing the community could have done here is to have the "official" word be: "Don't be officious about this. It's inherently vague. Some things are."
By making headlines one day and contradictory headlines a few days later, the community perpetuates the unfortunate perception that officiousness is a big part of science.
Posted by: ElkGroveDan Aug 24 2006, 07:28 PM
Let's not forget the quiz-show contestants who will now lose the whole pot of cash by answering, "There are NINE planets, Regis."
Posted by: yg1968 Aug 25 2006, 03:56 AM
Alan Stern isn't too happy about all this. See this article:
http://www.space.com/scienceastronomy/060824_planet_definition.html
Posted by: Stephen Aug 25 2006, 09:28 AM
Oh I don't know about that. The whole episode would seem to give a whole new meaning to the term "mad scientists".
======
Stephen
Posted by: Stephen Aug 25 2006, 09:38 AM
Unfortunately a more likely scenario is that some kid will get up in class one day and say: "Excuse me, Miss Barringer, but my pop reckons there are nine planets. So why did you mark me wrong in the exam?"
If the textbooks change sooner or later all the kids will start talking about eight planets. They will certainly be required to answer "eight" or be marked wrong.
Something like that happened in Australia to what used to be called "Ayers Rock" until the powers-that-be decided it would be more politically correct to rename it "Uluru".
======
Stephen
Posted by: Greg Hullender Aug 25 2006, 02:16 PM
I still very clearly remember a teacher who insisted Saturn had 9 moons because that's what our 1950's-era textbook said, and who was unmoved by any other evidence. "Don't believe everything you read" was his catch-all response.
Reading the occasional AAAS article on the subject, I don't think American science teachers have gotten much better in the past 35 years. So I'd expect the kids to be more up to date.
That said, this has had so much publicity that even the lamest teacher can't have missed it. Even my guy read the daily paper. I shudder to think how he'd have explained this, though.
Posted by: JRehling Aug 25 2006, 03:24 PM
Reading the occasional AAAS article on the subject, I don't think American science teachers have gotten much better in the past 35 years. So I'd expect the kids to be more up to date.
That said, this has had so much publicity that even the lamest teacher can't have missed it. Even my guy read the daily paper. I shudder to think how he'd have explained this, though.
I got to thinking about how much total time a child will hear about the solar system in a K-12 education, and how much of it will now be devoted to talking about this stupid planet definition issue, and what information that waste of time will displace. Chances are, the child will not hear about dust devils on Mars... but will hear that Pluto is really small. They won't hear that Jupiter has huge lightning storms, but they'll hear that astronomers voted on what is a planet.
I'm less concerned that a teacher will explain this matter "correctly" than that it will waste class time at ALL. I'd say if you had ten-minute blocks of lessons, and you wanted to correctly place the importance of this issue, it would be somewhere past #500, but instead it's going to end up in the top ten. And instead of a kid getting the idea that beautiful, exciting, dynamic, landscapes are out there, they'll get the idea that there are rules and definitions that must be adhered to. It's a tremendous shame.
Posted by: odave Aug 25 2006, 03:57 PM
IIRC, my 3rd grade daughter's class spent about a week of their science time on the solar system last year. Since it's been all over the media, questions are bound to come up, so unfortunately it should be covered. Depending on how the teacher wanted to handle it, they could probably get through the discussion in 10-15 minutes. That may blow half of a day's science lesson, but you've still got the rest of the week for more important things.
Posted by: Stu Aug 25 2006, 09:22 PM
Hmmm... 10-15 minutes to explain how Pluto was predicted, then found; how astronomers looked for then found KBOs; how there was a worldwide astronomical debate, lasting decades, about the identity of Pluto, at the same time as small group of planetary scientists fought desperately for NASA to send a mission to Pluto, and succeeded in launching it just before a visionary and controversial proposal was put forward to expand the solar system, which was then shot down and replaced with what many see as a painfully politically-correct compromise that in turn led to a suspiciously undemocratic vote which finally ended with Pluto being evicted from the list of planets, to the disgust and outrage of many...
If I heard from my kid that a teacher had raced through all that in 10-15 minutes I'd want them slapped with a wet fish and made to do the lesson again.
Posted by: JRehling Aug 25 2006, 09:48 PM
If a school does spend a total of 5 hours on the solar system, even 15 minutes for Pluto's planet status is way too much. That's 5% of the total time. Here are nineteen things that deserve mention:
Sun, Mercury, Venus, Earth, Moon, Mars, Asteroids, Meteors, Jupiter, Io, Europa, Saturn, rings, Titan, Uranus, Neptune, Triton, Pluto-Charon, comets.
Granted, some of these things will get a brief mention only, but Mars and Titan among others could be topics dealt with at length.
Space exploration itself could eat an hour. The planet-status topic is going to bump something far more worthy off the list.
Posted by: Big_Gazza Aug 25 2006, 11:19 PM
Yeesh! Too much concern over a non-issue. Anyone would think that the government has re-introduced prohibition from all the doom and gloom.
Folks, lets get it into perspective. The world hasn't changed. Tomorrow the price of petrol will be the same, the taxman will be just as greedy, the government will just as incompetant, and women will still defy understanding
Pluto is where it belongs. The flag bearer for the little guys. The icy rocks that never amounted to much. Its not a real planet, but it took us 7 decades to realise that.
Consider the alternative. The year is 2360, and little Johhny is having trouble remembering the names of the planets. He is OK until he gets to the double planet of Brangelina & Tomkat at 57 AU (number 31 in the list) but it gets hazy after that. He gets frustrated, gives up on school, and drifts into an aimless life of vice, crime and illegal drug use, forever haunted by the infamous decision by the IAU in 2006 where sanity just did not prevail.
Posted by: Bill Harris Aug 25 2006, 11:19 PM
My opinion? They are loonies.
There may be good logic for not designating the KBOs and other minor Solar System objects as planets, but Pluto ought to be a special case since it was discovered and named in the pre-interplanetary probe era and should be "grandfathered" in.
My 2c.
--Bill
Posted by: ugordan Aug 25 2006, 11:27 PM
So was Ceres.
Geez. this debate will never end, for as long as Pluto exists. Therefore, I suggest we blow it up. No Pluto, no problem.
Posted by: Stu Aug 25 2006, 11:34 PM
You see, this is the problem, right here. We're all happy with the idea of a school spending just 5 hours teaching about the solar system. 5 hours! That's NOTHING!
I wasn't suggesting for a moment that the Pluto-related items I listed should be taught at the expense of other astronomical subjects, phenomena and places, far from it. I was trying to say that astronomy is such a huge, huge subject that every planet deserves more than a mere "10-15 minutes". Jeez, I spend whole mornings and afternoon running junior school workshops about the solar system, and have to force myself to keep Mars' section under control as I could easily spend the whole session just talking about Valles Marineris!
This is a real "grrrr!!!" of mine, the quality of science education in schools. I can only speak from experience of schools over here in the UK, but "space" is taught appallingly, almost non-existently. There are token efforts made to cover the subject, at best. If the Pluto debate is the catalyst for improving that then yaaaay, I'm all for it. I just worry that what's more likely is that teachers - those that can be bothered - will take the debate as a sign that Pluto's not even worth bothering with to astronomers, and sweep it under the carpet, dismissing it as an iceball.
Posted by: odave Aug 26 2006, 01:02 AM
I was thinking of 8-10 year old elementary students, so the classification discussion doesn't have to be quite so detailed. I totally agree with that even that's too much to spend on this matter, but the cat's out of the bag. I'll be paying closer attention than normal to what happens in class when space comes around again this year. I'm sure the better teachers will make an effort to balance the time on the issue and "get it right", but unfortunately I feel a majority of them will teach straight from the book, or worse, straight from the standardized test.
And kudos to Stu for doing those workshops! I've done several astronomy nights myself, and I've always found the students & teachers very appreciative of the extra exposure.
Posted by: alan Aug 26 2006, 01:38 AM
DON'T DO IT
If that much plutonium (1.3 * 10^22 kg) was detonated it would release 10^36 Joules. More energy than the sun produces in 88 years.
Posted by: Myran Aug 26 2006, 07:24 AM
Thats correct, Ceres was declared to be a planet at first. One reason for that was that it fitted in the right slot for the idea of the now defunct 'Titus-Bode law'. But also that the size wasnt known.
So
1: Demoting one object of the planet label have been done before.
2: It happened when the true size of the object began to be obvious.
The same happened to Pluto in a step by step process after Charon had been discovered. The estimated size was downgraded and after the set of eclipses we had a the size nailed down.
Yet I agree with Bill Harris that we might have been able to keep Pluto, I would have liked that personally. The only good point I have for that is that Pluto are inside the actual belt of KBO's, but little other pro's. The list of cons starting with the elliptical Neptune crossing orbit & out of the ecliptic gets uncomfortably long - so its not about logic or facts but only 'sentimental' reasons.
Now what if someone actually do discover lets say one object in or close to the plane of the ecliptic and a near circular orbit & 5000 km diameter out there?
Well even I would give up my stance about that one not might be one KBO's that makes up same belt and depending on how many ways it qualify have to say that it instead are a never finished protoplanet or actual planet embedded in same belt.
Posted by: MCS Aug 26 2006, 08:03 AM
Geez. this debate will never end, for as long as Pluto exists. Therefore, I suggest we blow it up. No Pluto, no problem.
If only there were a handy Death Star around:
"Foolish earthlings, quibbling over such trivial matters. I will settle this argument for them. Permanently."
It would keep astronomers busy cataloguing all the new KBOs!
Posted by: ugordan Aug 26 2006, 11:21 AM
That's easy -- I wonder if Mimas can be reactivated after being unused for such a long time. We all know it's not actually an ordinary moon of Saturn...
Posted by: Bill Harris Aug 26 2006, 12:48 PM
>The same happened to Pluto in a step by step process after Charon had been discovered.
Yes, and Pluto has been teetering on the fence for a while as folks considered it to be an escaped moon of Neptune.
--Bill
Posted by: tasp Aug 26 2006, 02:52 PM
Am I alone in wondering why this IAU edict is even happening in this time frame?
Pluto has been on the planet roster for a very long time now, could this matter have been tabled till after the New Horizons flyby?
If Pluto turns out to have geysers, weather, climate, tectonics, lakes, volcanoes, lightning, aurorae, rings, hurricanes, magnetic field, etc. perhaps there would be a new debate regarding what a planet is?
Posted by: ugordan Aug 26 2006, 03:37 PM
Titan likely has most of those things, but I don't see such a fuss pushing for it to be a planet. I don't think interestingness should be a factor in determining what is a planet. Nor do I think being a planet should be a factor determining if something's interesting.
Posted by: David Aug 26 2006, 04:36 PM
You haven't been listening to Jason!
Posted by: ugordan Aug 26 2006, 04:40 PM
Nah.. He also hates Europa, so go figure!
Posted by: Jeff7 Aug 26 2006, 04:56 PM
Too many of those teachers are probably completely unaware that Pluto has its very own flyby mission en route.
"Foolish earthlings, quibbling over such trivial matters. I will settle this argument for them. Permanently."
It would keep astronomers busy cataloguing all the new KBOs!
But the Empire would only be interested in blowing up Charon.
Yes, and Pluto has been teetering on the fence for a while as folks considered it to be an escaped moon of Neptune.
--Bill
The other half of the proposed Triton duo perhaps? What I refer to is of course the theory that Triton was a wandering object, with a partner, and when they got too close to Neptune, Triton was captured while the other one was flung away.
Posted by: AlexBlackwell Aug 28 2006, 06:40 PM
Mike Brown is the guest for the http://planetary.org/radio/show/00000199/ of Planetary Radio.
Posted by: djellison Aug 28 2006, 07:13 PM
He even said that there is every chance we will find something the size of Mars or even Earth..but we'll have to call it a dwarf planet.
That's just astonishingly short sighted.
Doug
Posted by: volcanopele Aug 28 2006, 07:26 PM
That's just astonishingly short sighted.
Doug
See, that to me, sums up why I really dislike this definition. Personally, I don't think it is THAT big of deal whether or not Pluto remains a planet, but in the attempt to remove Pluto, they have shut the door for all intents and purposes on the possibility of finding planets in the cold deep. And we aren't just talking about problems for Mars and Earth-sized objects, even larger objects far out would have problems clearing their neighborhoods as go farther out.
Posted by: djellison Aug 28 2006, 07:28 PM
I to don't really care if Pluto is or isn't a planet...but I DO care when the definition they've come up with is so flawed and counterintuitive.
Doug
Posted by: climber Aug 28 2006, 07:36 PM
Now, in the books, NH will be seen as a new class of explorer
We have had :
Spoutnik 1 to the Earth
Luna 1 to the moon
Mariner 2 the first to a planet
Pionner 10 the first to (outside planets and) outside the solar system (may be Voyager 1's better pick)
Giotto to a comet
...you can complete the very limited list of "new explorers"
In that sense, its very name "New Horizon" couldn't have been a better choice. I personaly don't mind whether Pluto is or isn't a planet, I want to understand our solar system and how it compares to others. Go NH, Go, tell us what's up there.
Posted by: jamescanvin Aug 28 2006, 09:41 PM
Yup, that's been my other big problem (after the whole neigbourhood clearing issue) with all this.
Dwarf Planet: Not necessarily a dwarf and definitely not a planet.
Talk about confusing. Worst name ever!
Posted by: gpurcell Aug 28 2006, 11:01 PM
My wife tolerates my space exploration obsession, teasing me about going to JPL websites and the like. She's your basic, educated person for who space is at most a passing thought.
This Pluto thing got her pissed off enough to rant about it. Which is surprising.
Her beefs:
1) What the heck is the "IAU" and who gave them the authority to determine something like this?
2) Historical precedence ought to count for something.
Getting her riled up is an indication of how foolish this decision was.
Now, I'm not an astronomer. But I am a political type, and from my professional perspective this issue was handled incredibly poorly.
First, the IAU did not have to create a set of exclusive definitions. Doing so ensured that the Pluto decision would be a hardball choice over which there could be no compromise. That's a bad situation to be in. The original committee suggestion was quite clever in this regards; by keeping Pluto a planet, while including it in a separate category, the path was laid out for the gradual elimination of it. Without a fight. As the planets of the KBO proliferated, the shorthand would have become: "We have eight classical planets and ### "plutons" beyond Neptune of which we know the most about Pluto." In a generation or two, Pluto and the rest of the planets are separated.
Second, the whole rejection of the committee report was a really bad scene. It looks like a cabal of anti-Pluto types threw out a lot of serious work and imposed their policy preferences over the vocal objections of a significant minority. The small group that actually voted on this only adds to the sense that Pluto was convicted in a kangaroo court.
Third, and this bears on my wife's first point: the IAU has nothing but its internal credibility behind its decisions. By engaging in a hack job on this issue, that credibility has been undermined significantly. That lack of credibility is likely to bear noxious fruit in a host of policy choices: "Well, you all can't even decide what a planet is, when any sixth grader can tell you that! So why should this Congress give you more money?"
In summary, it was exceptionally foolish to allow astronomers, untrained in linguistics, semantics, or politics to have free reign in determining the answer to the Pluto question. The IAU obviously realized this with its initial committee selection. It is most unfortunate that the professional anti-Pluto crowd did not take their advice into account in favor of their ill-considered jihad.
Posted by: mars loon Aug 28 2006, 11:24 PM
That's just astonishingly short sighted.
quote:Today, 07:28 PM
I to don't really care if Pluto is or isn't a planet...but I DO care when the definition they've come up with is so flawed and counterintuitive.Doug
I completely agree and even Mike admits on his website that the definition is flawed.
This is a complete PR disaster for astronomy and science as evidenced by the endless cartoons, polls, etc. So now the public will have even less respect for scientists. As a scientist, I dont see much positive here for science or public understanding of science.
gpurcell's wife is typical of public reaction.
The IAU vote should have tabled this for a later date, given all the internal controversary. Doing nothing or trying again to reach broader consensus would have been better than being hijacked at Prague by a narrow band.
Posted by: mchan Aug 29 2006, 04:23 AM
I had thought this as well but did not post it in such a clear and succint way. The effects of the original proposal would indeed be spread out and evolve over time. Even the cultrual planet might diverge from the scientific planet, with Pluto being a cultural planet and not a scientific planet.
Posted by: karolp Aug 30 2006, 01:59 PM
And how about having "cultural" bacteria versus "scientific" bacteria? Or "cultural" mammals vs. "scientific" mammals? All in all planet was supposed to be a scientific word. It had only become a cultural one because underfunded science cannot provide much details on what a planet really is so culture filled in.
Posted by: djellison Aug 30 2006, 02:12 PM
To use the biological analogy 'Planet' is like 'Bug'
Bug can mean all sorts of things in common english - Bacteria, Virii, small insects etc etc.
In common english - Planet can mean Terrestrial, Gas Giant, KBO etc etc etc.
Perhaps there's an argument to be made for not trying to define the word 'Planet' at all.
Doug
Posted by: karolp Aug 30 2006, 03:11 PM
gpurcell's wife is typical of public reaction.
The public does not typically have much understanding of such things as the Kuiper Belt. For them that is pure technobabble. They simply know that Pluto was discovered by an American and has the same name as Disney's cute cartoon dog. They tend to run into a weird "overpersonification" of Pluto defending it from "bullies" and demanding it to be treated like "any other". It was already obvious what Pluto is with the discovery of 1992QB1 in 1992 (the first known KBO). And if that was not enough, discovering Xena - a KBO larger than Pluto did it. Mike Brown - Xena's discoverer and Kuiper Belt explorer understands that. The "public", as well as non-planetary, non-KBO astronomers - don't.
Posted by: JRehling Aug 30 2006, 04:27 PM
What about "river"? "Mountain"? "Canyon"? Those are all vaguely defined.
I hardly think more funding would shed a lot of light onto this. Maybe whopper projects in Earth-based telescopy to search for more far-out objects.
Posted by: gpurcell Aug 30 2006, 05:30 PM
I disagree. Planet was a word for a category of objects long before science came along.
Definitions are, at some level artificial constructs. There is no "scientific" answer to the question "What is a planet?" because the question itself is not one with truth value. Given a set of criteria, science can determine whether an object matches or fails...but the criteria used are, in the end, subjective.
Posted by: dvandorn Aug 30 2006, 06:23 PM
Very true. If we want to go back to the original definition, a planet is any point of light in the sky that "wanders," i.e., that does not move in the same manner as the stars within the celestial firmament. If we go back to that definition, then any solar system object, no matter how small, that is visible from Earth is a planet.
I guess we could debate whether or not an object must be naked-eye visible to qualify...
-the other Doug
Posted by: karolp Aug 30 2006, 06:50 PM
I guess we could debate whether or not an object must be naked-eye visible to qualify...
-the other Doug
I don't think going back to the original idea devised by the Greeks to be a good idea. All in all the word has certainly evolved and gained some scientific meaning. But the meaning is not complete as we do not know many exotic configurations which might occur in other planetary systems. And by underfunding I mean cancelling such missions as the Terrestrial Planet Finder developed by NASA. But luckily ESA has its COROT mission which is also specifically designed to hunt for exoplanets and it is due to be launched in October 2006
Posted by: David Aug 30 2006, 06:52 PM
I consider the (apparent) fact that I am able to discuss this planetary classification issue halfway intelligently to be positive proof that it is not in any sense a scientific question.
Posted by: karolp Aug 30 2006, 07:29 PM
And it won't really be until we find out what a planet REALLY means by exploring other planetary systems and seing what they are like and might be. I particularly find any criteria of circular orbits to be inappropriate and Sol-centered - there are "jupiters" and "neptunes" in eccentric orbits around other stars. But we shall not understand what it really means to "be a planet" until we see more planets around other stars. For now it is just a "distant flavour", not insight. But we ARE intelligent enough to tell a KBO from a planet. And until COROT tells as some more or we discover an "earth" in the Oort Cloud the case appears to be settled.
Posted by: Greg Hullender Aug 31 2006, 02:19 AM
Something I thought sounded interesting in one of Mike Brown's papers was the idea that a "planet" in a really eccentric orbit is probably a separate condensation from the original nebula, not a condensation from the accertion disk of the star. Multiple stars do indeed tend to have very elliptical orbits, so a "planet" that condensed that way would likely have one too. He alluded to a "purist" view that insists all such bodies are "stars" not planets, although he didn't sign up to it.
The implied assumption (sounds reasonable, anyway) is that anything that does form from the accretion disk will unavoidably be in a circular orbit near the plane of the ecliptic.
Posted by: alan Aug 31 2006, 04:36 AM
The web is being rearranged to accomodate the new definition: eightplanets.org and now redirects to nineplanets.org 
Posted by: karolp Aug 31 2006, 01:09 PM
Gas giants might get eccentric orbits from interacting with each other. It was suspected Uranus was coming close to Saturn in the past in its eccentric orbit which finally resulted in its odd tilt. Circular orbits are so "Copernican". Time to embrace the 21st c.
Posted by: Greg Hullender Aug 31 2006, 01:54 PM
Uranus and Saturn are both in less eccentric orbits than Mars. I've never heard anyone suggest that they used to be in more elliptical orbits. I HAVE heard the suggestion that they both formed further in and have gradually drifted further out, but that would have happened when the Solar System was new.
Posted by: karolp Aug 31 2006, 06:07 PM
Well, it basically goes like this:
"Jupiter and Saturn start out at roughly 5 and 8 astronomical units; Uranus and Neptune begin much closer to the Sun than their current positions, at about 13 and 14 AU. They stay pretty comfortably in those positions for about 100,000 years. Then, quite suddenly, that 1:2 resonance is reached. Saturn and Jupiter don't change a lot initially, but the orbits of Uranus and Neptune go nuts. They get much more eccentric, so that their orbits cross; at times Uranus even gets very close to Saturn. After about a million years, the eccentricity dies down, and Uranus and Neptune are on their way out to more distant positions in the solar system, at the same time that Saturn begins to acquire its present orbit eccentricity."
http://www.planetary.org/blog/article/00000553/
Posted by: ugordan Aug 31 2006, 06:42 PM
I have a problem with that scenario. Namely, Saturn, Uranus and Neptune start closer in than they're now.
* Saturn : 8 AU --> 9.5 AU
* Uranus : 13 AU --> 19 AU
* Neptune : 14 AU --> 30 AU
All three are gaining momentum as they move into a higher orbit. Who's losing momentum here? You can't just get it out of nothing. There has to be a pretty large object that spirals inward as a consequence. I see Jupiter stayed pretty much where it is now so no luck there.
Posted by: Alan Stern Aug 31 2006, 07:15 PM
Actually, the simulations show U and N get up to e=0.3 or a bit higher en route from their former closer orbits to their current ones.
This occurs just after their strong scatterings by J or S and before dynamical friction on the outer disk damps the e back down.
Posted by: Greg Hullender Sep 1 2006, 03:24 AM
Thanks, Alan. I knew the move had to be while there was still a lot of material in the accretion disk, but I had envisioned a gradual outward spiral. I hadn't considered a catastrophic interaction, but I guess I shouldn't be surprised.
How confident are astronomers/astrophysicsts of this simulation?
Posted by: Alan Stern Sep 1 2006, 03:46 AM
How confident are astronomers/astrophysicsts of this simulation?
Its controversial that U and N originated in the J-S zone, but the simulations of that are convincing
that if this occured, the e's got pretty high. I myself am not convinced of the entire scenario.
-Alan
Posted by: Jyril Sep 1 2006, 10:51 AM
Isn't it that according to the theories of planetary formation, Neptune should still be in the process of forming if it formed where it is now?
Posted by: Alan Stern Sep 1 2006, 11:04 AM
No. I think you're confusing the fact that in many old models, Neptune could not be made for form in
the age of the solar system. It has no significant feedstock to continue forming today in any real
sense, though technically it and all the planets--including Pluto--are gaining mass because things that
they run in to "stick" owing to their high gravity.
-Alan
Posted by: Myran Sep 1 2006, 01:41 PM
I am not entirely convinced of this scenario either.
One detail that makes me wonder are the fact that the disc where the planets formed should have been thinner at the outer edge. Yet Uranus have got 14 earth masses whereas Neptune got 17.
But there could of course have been a thicker belt of KBO's that Neptune gobbled up when it migrated outward and so gained more mass. The KBO's are after all just that, planet bulding blocs and if there was enough of them and we smashed them together we'd end up with something quite similar to Uranus or Neptune: A small rocky core surrounded by a vast and very deep ocean and perhaps even a similar atmosphere, at least it would have the methane.
If this scenario would be correct, then Chiron and Pluto simply are the leftovers which happened to survive with Pluto in resonance with Neptune and Chiron flipping back between Uranus and Saturn.
Posted by: Julius Sep 1 2006, 07:21 PM
This Migrating Giant theory was clearly discussed on BBC sky at night programme.While N,U and S seem to be migrating outwards,is J supposed to be moving inwards towards the inner solar system?If I understood right,interactions with KBOS seems to be the trigger of this whole migration taking place with Jupiter being the final encounter resulting in KBOS being scattered into the interplanetary space.Would this explain the presence of Phoebe at Saturn??
Posted by: Julius Sep 1 2006, 07:34 PM
Sorry I have been away for a while!Is that THE real ALAN STERN?I have a question:Since Charon,nix and Hydra seem to have originated from impacts with Pluto,would it be reasonable to assume that we should be seeing big impact craters on Pluto,unless of course there is some process that is refreshing the surface to obliterate such major events??What are the predictions if any have been made??
Posted by: Alan Stern Sep 2 2006, 04:31 AM
THe giant collision that produced Charon, Nix, and Hydra did not leave an impact scar because it remelted
Pluto. For KBO collisions and cratering predicts on Pluto and Charon, see Durda & Stern (2000) in
Icarus; I belirve these remain the latest model calculations.
-Alan
Posted by: djellison Sep 2 2006, 07:12 AM
I guess one could use the Earth / Moon formation as an analogy. We don't see a enormous crater on Earth from the impact that created our moon.
(and yes - that's the real Alan )
Doug
Posted by: Jyril Sep 2 2006, 09:36 AM
http://www.psrd.hawaii.edu/Aug06/cataclysmDynamics.html AlexBlackwell posted earlier.
Posted by: Julius Sep 4 2006, 12:20 PM
Thanks for your feedback Alan,much appreciated.I dont agree with the 'Pluto is Dead' title to this forum.Pluto is more alive than ever.Until recently. no one could ever dream of having a probe flying toward Pluto and perhaps other KBOS.Planet or not,doesnt matter....whats in a name???
Posted by: djellison Sep 4 2006, 12:46 PM
I think that's the point
Those are Mike Browns words - and I think the majority in this forum disagree with them.Doug
Posted by: Alan Stern Sep 4 2006, 01:02 PM
This thread reminds me of the old thrust and parry:
"God is dead" --Nietzsche
"Nietzsche is dead"-- God
We'll see where the planet debate ends.
Posted by: DonPMitchell Sep 4 2006, 09:30 PM
I think we should vote again. Amateur enthusiasts get one vote. Professional astronomers get 2 votes, and people who have launched a probe to Pluto get 100 votes. :-)
Posted by: Alan Stern Sep 5 2006, 12:17 AM
If only.
Posted by: Julius Sep 5 2006, 07:47 PM
Planet or not,no big deal!To be honest I was not particularly keen about having the solar system numbering 13 planets as was being suggested prior to the voting.I believe that Pluto's proper place lies with the KBOs.Personally,Pluto has not been demoted or anything.My interest in NH has not dwindled .I would like Pluto to look like Triton of Neptune;Surely that would be interesting provided that NH will have 6 months of observations whereas Voyager just flew by Triton over a matter of days. Wish we had more time with Triton.Hope to be around in 2015 to see the Plutonian system.
Posted by: ugordan Sep 5 2006, 09:41 PM
I think that's a bit incorrect. Voyager 2 began observing both Neptune and Triton well in advance of the closest approach date. Take http://photojournal.jpl.nasa.gov/catalog/PIA01491, dated July 3, it's a month and a half before August 25, C/A date. NH will also fly by Pluto in "a matter of days", but that doesn't mean an extensive observation campaign won't take place before.
Posted by: SigurRosFan Sep 7 2006, 01:15 PM
134340 - Pluto's minor planet number.
Posted by: karolp Sep 7 2006, 01:22 PM
And where does that come from? Is it the next unassigned number? How about 90210...
Posted by: Jyril Sep 7 2006, 03:46 PM
Go to http://cfa-www.harvard.edu/iau/MPDes.html and type "Pluto" and you'll get
Additional identifications = Object Lowell Observatory = X
Posted by: volcanopele Sep 7 2006, 04:45 PM
When does Earth get its minor planet number? ....
Posted by: Rob Pinnegar Sep 7 2006, 05:21 PM
A completely unremarkable number. They should have given it 0 instead.
Posted by: SigurRosFan Sep 7 2006, 05:30 PM
And "Xena":
---
(136199) 2003 UB313
No additional identifications
---
Posted by: Jyril Sep 7 2006, 05:38 PM
Six years ago, somebody suggested that Pluto should have assigned with the minor planet number 10000. It would have become the first numbered & named KBO. The suggestion resulted in an uproar and was forgotten. The number 10000 went to a completely unremarkable main belt asteroid and now Pluto got a dial number.
It's obvious that no one will use it perhaps except for articles and such, so in practice it is more or less irrelevant what number it gets. But still this feels humiliating.
Posted by: ugordan Sep 7 2006, 05:53 PM
Or 00. http://en.wikipedia.org/wiki/Wacky_Races would have liked that one.
Posted by: alan Sep 7 2006, 08:18 PM
Explanation from minor planet center, (or should that be dwarf planet and small solar system body center )
URL http://cfa-www.harvard.edu/iau/mpc.html ISSN 1523-6714
EDITORIAL NOTICE
(From MPC 57525)
At the IAU General Assembly in Prague on Aug. 24 a very substantial majority of the members present agreed to accept that the solar system contains just eight "planets" (Mercury-Neptune) and that objects in hydrostatic equilibrium orbiting the sun but not dominating their vicinity would be considered as "dwarf planets". (1) Ceres, Pluto and 2003 UB313 were identified as members of this new category, with other objects such as 2003 EL61 and 2005 FY9 likely to be added in the future. Since at least one of the "dwarf planets" is already included in the catalogue of numbered "minor planets"--with comets and other natural sun-orbiting material a component of a new category of "small solar-system bodies"--and since the Minor Planet Center Terms of Reference emphasize the need for the MPC to maintain a database of the astrometric observations of such bodies observed beyond the confines of the earth's atmosphere, Pluto and the above-mentioned three provisionally designated objects are now being added to this list of objects with reliable orbit determinations under the numbers (134340), (136199), (136108) and (136472), respectively. It should be noted that, just as some of the numbered objects that have exhibited cometary activity also have designations in the catalogue of numbered periodic comets, the numbering of "dwarf planets" does not preclude their having dual designations in possible separate catalogues of such bodies.
Timothy B. Spahr © Copyright 2006 MPC M.P.E.C. 2006-R19
Pluto still doesn't show up on their list of transneptunian objects though.
Posted by: tedstryk Sep 7 2006, 11:44 PM
This is idiotic. If dwarf planets are going to be considered a new type of object, why are they numbering them like they were asteroids? They don't number comets on the same system as asteroids, and they don't number moons around different planets on the same system. So why do it here, when there are already thousands and thousands of asteroid numbers?
Posted by: David Sep 7 2006, 11:56 PM
We sometimes forget how important names are, and how words help us organize things in our minds, and influence our prejudices.
For instance, for most people "Pluto" was and is a plausible planet. However, "Asteroid #134340" is just a nothing, a little rock on the edge of nowhere. Assigning a number -- and in particular a nondescript, license plate-style number -- has obvious propaganda value. Nobody wants to memorize "Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, 134340."
Posted by: AlexBlackwell Sep 8 2006, 04:37 PM
I wasn't sure where this post would fit, so I placed it here. Bill Safire joins the fray in his On Language column in the September 10, 2006, issue of The New York Times Magazine:
On Language
Dwarf Planet
By WILLIAM SAFIRE
The New York Times Magazine
Published: September 10, 2006
http://www.nytimes.com/2006/09/10/magazine/10wwln_safire.html
Posted by: gpurcell Sep 8 2006, 04:46 PM
Boy, those bastards at the IAU and MPC really know how to rub salt in a wound, don't they!
Posted by: Alan Stern Sep 8 2006, 07:50 PM
Perhaps a little feedback to Dan Green and Brian Marsden at MPC is in order, your call.
marsden#cfa.harvard.edu
green@cfa.harvard.edu
Posted by: AlexBlackwell Sep 8 2006, 09:43 PM
I apologize if this has been mentioned but I just noticed Paul Schenk has an interesting editorial, "Pluto Demoted Back to Dog-Star Status," which appears in the August 2006 issue of the Lunar and Planetary Information Bulletin (http://www.lpi.usra.edu/publications/newsletters/lpib/current.pdf).
Posted by: mchan Sep 9 2006, 08:24 AM
Alan Stern's PI's Perspective for September 6 keeps Pluto as ninth planet --
http://pluto.jhuapl.edu/overview/piPerspectives/piPerspective_current.php
Posted by: alan Sep 9 2006, 08:27 PM
If your going to count the dwarf planets as 'real' planets wouldn't that make Pluto the tenth planet?
Posted by: JRehling Sep 10 2006, 04:12 AM
Sorting by what? Discovery: ninth. Distance: ninth. Size: tenth.
Posted by: Greg Hullender Sep 10 2006, 04:32 AM
I think he's including Ceres, which makes Pluto 10th in discovery and distance. If you include "Xena," it's tenth in size. Hard to make any principled argument that it's the 9th planet -- other than tradition, which can't really be called "principled."
Posted by: alan Sep 10 2006, 03:44 PM
Traditionally, back in the 1800's, Ceres, Pallas, Juno, and Vesta were listed in almanacs and journal by order of semimajor axis between Mars and Jupiter. For a while this made Jupiter the 9th planet and Neptune the 12th. After many more were discovered in the mid 1800's a numbering scheme was created and the new asteroids were put at the end in order of discover which was more convenient.
Marsden proposed giving Pluto minor planet number 10000 for a similar reason: he thought it would be more convenient if it was included in the minor planet database because Pluto kept being 'discovered' by automated asteroid search programs.
Traditionally, when a planet is found to be part of a large group, or belt, of objects it becomes part of that category instead of a planet. See the "unjust demotion' of Ceres for example.
Posted by: JRehling Sep 10 2006, 08:10 PM
That's not a truism and an example. That's a "rule" induced from a single example. If we had found a 10-25 earthmass body about every 10 AU out past Neptune, I doubt if the fact that they constituted a large group would have led anyone to revoke the "planet"hood of all of them, along with Uranus and Neptune, too, leading us to conclude that Mercury through Saturn were planets, but Uranus, Neptune et al were not.
When we try to induce why Ceres was demoted, we're theorizing in cognitive science. Which is actually the proper field for all of this, not astronomy.
To go down that road, the many-ness of the MBAs (main belt asteroids) was a likely factor, but size was as well, with Ceres being about 19% the diameter of Mercury. (A history of the accuracy of those measurements would be interesting; I don't have that information, but I don't think it fluctuated as wildly as the Pluto size estimates.) If it had turned out that the MBAs had many objects about the size of or larger than Mercury, then I guess we would have had a "is Mercury a planet?" debate 150 years ago. The large gap between Mercury and Ceres prevented that.
If it turned out that Pluto were about the size of Earth and we had kept finding KBOs that totally closed the size gap between Earth and boulder, howevers, I don't think we ever would have had the "is Earth a planet?" debate. Well, except for much earlier when it was realized that Earth was a globe surrounded by space instead of a planar surface overlying Hell.
The essential matter is that it seemed reasonable c. 1850 to exclude some small bodies from planethood, and the then-apparent gap made it look like nature had handed us some natural categories. The current embarrassment comes from the fact that the "natural category" assumption is not being questioned. Appealing to quantities that had never been a part of anyone's definition in order to reverse-engineer a desired outcome isn't good astronomy, good cognitive science or anything.
Posted by: john_s Sep 12 2006, 12:47 PM
Well here's my contribution to the debate...
http://www.planetary.org/blog/article/00000694/
John.
Posted by: djellison Sep 12 2006, 12:55 PM
We gloggers all have to have a bit of input into the debate Jim had a go at it, so did Rosaly, now your turn....I'm hoping that by October, the IAU will have reduced the status of Pluto to that of a large onion so I can have a stab at the subject as well
Doug
Posted by: ugordan Sep 12 2006, 01:04 PM
I like it. It looks as one of rare positive views on the whole definition thing. Most others just seem to bash the planet definition not because it's plain bad (though I admit, it is sloppy), but because Pluto isn't a planet anymore and they're just trying to find reasons to attack it. I get the feeling they'd be more than willing to live with the definition if Pluto remained a planet by the definition's standards.
Just my 2c...
Posted by: odave Sep 12 2006, 01:44 PM
Very well written, John. I agree that the "neighborhood clearing" statement is clumsy. If they'd taken the time to word that phrase better, IMHO, fewer teeth would have been gnashed.
Thanks for your perspective.
Posted by: JRehling Sep 12 2006, 04:50 PM
John, your statement of support is probably the best I've seen... which means it's the best place from which to try to take the discussion further.
Let's say that one principle is that a meaningful category can be induced when a large gap is seen in the sizes of the objects within a local population. In the inner solar system, we have a gap between the size of the Moon (or Mercury, if you want to exclude non-solar-primary orbits) and the largest inner-SS asteroid (which is about 5 km in the longest axis?). In the outer solar system, we have a large gap between Uranus/Neptune and Ganymede, or (sun-primary-only) Xena. Past Neptune, we have no such gap (smooth continuum from Xena down to gravel, probably).
A problem I see with your explanation of the current definition is that these are two or three different populations. It's fine to come up with a term that distinguishes Mercury, Venus, Earth, and Mars from the Apollo, Aten, and Amor asteroids, and another that distinguishes Neptune from Pluto, but there are two unexplained conceptual leap:
That local-relative size is the sole distinguisher of a category that has global (for the inner solar system, for the outer solar system, and possibly elsewhere: "planet" in all cases).
Suppose we found, way out there, an zone with tight concentric orbits with sixteen 10-Jupiter-mass-sized objects, and one Venus-sized object. The gap between the "biggies" out there and the Venus-sized object is bigger than the gap between Neptune and Xena, and I think this brings out the problem with the "local qualification... global term" problem. Now the far-out Venus is not a planet, but the way-inside Mercury is, despite the former being absolutely larger.
This seems to me to be extremely hard to defend (aesthetically, which is what this exercise is all about). The original sin that begs for this problematic "local qualification... global term" quirk is, of course, the fact that the gas giants are so much larger than the terrestrial planets, but the terrestrial planets are not that much bigger than the big KBOs. To spell out the numbers, and to focus on size alone, the geometric mean of the radii of Neptune and Pluto falls between that of Mars and Venus: Mars is more "like" Pluto than it is like Neptune. Certainly Pluto and Xena are more like Mercury than Earth is like Neptune.
The "local qualification... global term" problem fixes the answer a certain way by comparing Xena and Pluto to Neptune, but comparing Mercury only to Icarus and Geographos.
As you note, the definition is already counting on there to be no big KBO out there that muddies things. But Sedna may already do that, by working the "local" loophole, with nothing else (maybe) around it. And a really big KBO would attack the "global" problem with the definition. But we can see the problem without even having those new discoveries turn up.
Posted by: Superstring Sep 12 2006, 11:38 PM
This is my first post here. I have thought long and hard about this debate, and although I am probably late in chiming in on this board, I do feel some things need to be said. Perhaps it already has been said, perhaps not.
First off, the problem with using dynamics as the fundamental characteristic in defining planets is simple: it is inconsistent. Each stellar system likely has its own unique dynamics, in fact a lot of them so far are rather different from our own Solar system. It doesn't make sense to make a definition that caters to only one system and no others. I know that's what the IAU did and intended to do, but I fail to see why. Our knowledge of other stellar systems is rapidly increasing and it won't be too long before a plethora of Earth-mass objects are found around other stars. So to me, it would make sense to go ahead and come up with a universal definition that is applicable to any system or place; otherwise, we're not really coming up with a definition per se, but more of a standby filler as we wait to gather more information.
The inconsistency in stellar system dynamics brings up several noteworthy, hypothetical scenarios. Systems with less accretion material, especially those involving small brown dwarfs as the center object, could easily have a Ceres-sized object that has "cleared its orbit." On the other hand, objects in our own system beyond Neptune are larger, and the possibility remains that a Mars or even Earth-size object in the region is waiting to be found. Yet, even these objects would be kept as dwarf planets merely due to location. It is worthy to note that had our system not had Jupiter or Saturn to absorb and slingshot material, the inner region very well could have consisted of a swarm of large objects as opposed to four, neatly-arranged worlds. The lack of such giant planets beyond Neptune is the reason why smaller bodies were able to spread out into the wide, chaotic region we know as the Kuiper Belt.
The actual criteria of "clearing an orbital neighborhood" is not only vague and suspect, it is arbitrary. What exactly constitutes a cleared orbit? Citing that one can see it and know it in our Solar system is not an acceptable answer since, as I aforementioned, it is best to come up with a definition that applies anywhere. Obviously, other stellar systems may not be so clear-cut on orbital dominance. Any boundaries we set regarding the width of a belt, maximum size ratios, etc will all be completely unscientific. Another issue with this is that it is difficult, if not impossible, to tell whether an exosolar object has "cleared its orbital neighborhood" or not. We could find several Earth-size planets, only to find out that all of them are "in a belt" and thus be forced to downgrade them to dwarf planets. Where is the logic in this? I should also point out that Sedna is currently the only object in its orbit. According the IAU definition, that technically makes Sedna planet, even though other objects are expected to be discovered in its region in the future.
Clearly, the definition needs to be based upon something more consistent, more applicable, and more scientific than dynamics and location. Some have suggested origin, but this will be even more difficult to determine and categorize. There is really no way of knowing how or where many of the known substellar bodies originated, so it would be ludicrous to base a whole classification off of that trait.
With all of this said, it is my opinion that the best option lies in the physical attributes of an object. Here is the definition of the word planet I have come up with, written in IAU style:
A planet is a celestial body that has (a.) sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium shape, (b.) restricted mass so that it cannot support or sustain fusion reactions, and (c.) does not contain degenerate matter.
In laymen's terms, a planet is any object that is rounded by gravity and is not, or never was, a fusor. That's it. This is simple, scientific, consise, and groups a large, intriguing class of objects in our universe under one name. I fully realize this includes moons; that is my intention. Moons that are pulled round are the same class of object as rounded objects that orbit a star. The only difference is orbit, and I stand by my case that orbital traits should be left aside from the broad definition. Titan is just as much a planet as Mars, as are Enceladus, Umbriel, Quaoar, Pluto. They are all planets.
Since I have made planet a broad term, sub-categories are needed. There are two fundamental and necessary ways to divide planets: orbit and size.
Based on orbit:
1.) A primary planet is a planet that orbits about a point within a star or any fusing object.
2.) A secondary planet is a planet that orbits about a point within another planet.
3.) A rogue planet is a planet that drifts freely through space.
Based on size:
1.) A giant planet is a planet that has sufficient mass for its self-gravity to sustain an envelope of light gases that make up the majority of its total mass.
2.) A terrestrial planet is a planet that has sufficient mass for its self-gravity to sustain an atmosphere from gases present in its hill sphere*, but restricted mass so that it is not a giant planet.
3.) A dwarf planet is a planet that has restricted mass so that it is not a terrestrial planet.
*This limit is approximately 10^23kg, just slightly lower than the masses of Mercury and Callisto.
It is correct, but not necessary, to combine the two sub-categories when describing a planet. For instance, Earth is is a primary terrestrial planet. Enceladus and Europa are both secondary dwarf planets. The nice thing with this is that it's very flexible. One can easily group all the terrestrial planets or dwarf planets without worrying about orbit; conversely, one can group all the primary planets with orbit largely in mind. Another benefit of adding the major moons into the planet category is it would give them more public credibility. For some reason, discussion about a moon does not seem as fascinating to many people as a planet. This is demonstrated by how the Solar System is taught; students learn the terrestrial and giant planets that orbit the Sun, plus Pluto and maybe some asteroids, but rarely do the moons get such attention. This is a good example of why limiting this kind of definition based on orbit is so problematic.
If this definition is applied, our Solar System contains about 50 planets and likely more to be added beyond Neptune. In all honesty, I must ask: what's wrong with this? Astronomers aren't afraid to have billions of stars or billions of galaxies, but then the idea of a couple dozen planets is scary? This is flawed science. I imagine it stems from the notion that Earth is somehow in a special class of objects, but in reality, a planet is what it is. I also find it preposterous that Pluto and other similar round bodies don't qualify because they are too small. If we're going to get strict about size comparisons, how about we take note how small Mercury is to Jupiter. The size ratio between the smallest terrestrial planet and largest giant planet is actually about the same as the size ratio between the smallest dwarf planet and largest terrestrial planet (Mimas and Earth, respectively). The giant planets are so radically different that to include Earth and its neighboring large bodies in the same class, meanwhile excluding objects like Pluto, is insane.
Two cents.
-String
Posted by: john_s Sep 13 2006, 09:29 PM
Point taken. We really have not eight "planets" but four "terrestrial planets" and four "Jovian planets", and lumping these very different categories together is a bit artificial. But the other constraint we're working under is to have a definition of "planet" that's not radically different from the one that's currently part of the culture, and our culture has lumped together these two classes since antiquity. The IAU definition makes only a small adjustment to what currently counts as a planet, while making the definition cleaner. Hypothetical future discoveries could muddy the waters, but a roundness-based definition, for instance, produces muddy waters already, with a dozen known bodies that hover near the planethood boundary and whose status will always be controversial. This may make for good publicity, but doesn't make for a good classification scheme.
Posted by: dvandorn Sep 13 2006, 11:47 PM
I'm not sure I agree with that characterization. I'd say we have four rocky planets, two gas giant planets, and two ice giant planets. Jupiter and Saturn are far more similar to each other than either is to Uranus or Neptune.
As an off-topic aside, we always hear that Jupiter and Saturn may well have rather small, rocky cores. Considering that most of the mass in the stellar disk probably migrated early to the gravitational center of the disk before the Sun ignited, is there a theory that the Sun has (or had) a rocky core in there somewhere? That would be a heck of a thing to see...
-the other Doug
Posted by: JRehling Sep 14 2006, 02:59 AM
There's a technique called cluster analysis: There's no doubt that in our solar system, with size as the constraint, Jupiter and Saturn would be nearest neighbors, as would Uranus and Neptune, Earth and Venus. I'm sure, however, that the JS pair and the UN pair would be linked before the UN pair would be linked to the EV pair. Neptune is almost four times the diameter of Earth, but better than 40% the diameter of Saturn.
Posted by: Rob Pinnegar Sep 14 2006, 04:41 AM
In a way I'm surprised that this argument hasn't come up more often. Just about everyone seems to include "Sun-circling body" in the definition of "planet", but it doesn't *have* to be that way, really. Certainly it's not difficult to think of Titan as a "planet" -- in fact it seems more like a planet than a moon, and the same goes for Io and Europa at least. The "Small Solar System bodies" category then becomes effectively "moons of the Sun" that aren't big enough to be planets.
By the way, on the topic of Doug's point about whether the Sun ever had a rock-metal core: The silicon-iron inner layers of red supergiants (just prior to Type II detonation) could probably be argued in this fashion, though of course that's a very different situation from the proto-Sun because those elements were formed in place rather than settled under gravity. As for the Sun itself, I guess it depends on how strong the convection was -- it's an interesting point.
Posted by: David Sep 14 2006, 01:00 PM
Now that's just what we need: a cladogram of the planets!
Which, I guess, would look something like this:
1.
1.1
1.1.1 Jupiter
1.1.2 Saturn
1.2
1.2.1 Uranus
1.2.2 Neptune
2.
2.1
2.1.1 Earth
2.1.2 Venus
2.2
2.2.1 Mars
2.2.2 Mercury
2.2
2.2.1
2.2.1.1 Eris
2.2.1.2 Pluto
2.2.2 -- All other minor planets and assorted solar debris
Every definition of planet proposed up to now has thus been paraphyletic -- and thus not really "scientific".
Posted by: alan Sep 15 2006, 11:30 PM
Slideshow showing relative size of various objects ranging up to largest stars. Pluto is mentioned. Takes awhile to download.
http://sizeofoutworld.ytmnd.com/
Posted by: laurele Sep 30 2006, 06:09 AM
- http://news.bbc.co.uk/1/hi/world/5282440.stm
"Pluto is dead???" What kind of ridiculous statement is that for a scientist to make? It sounds as if he believes he has the power to remove an object, no matter what it is called, from the solar system. Remember, "a rose by any other name..." It sounds like he is reflecting a personal bias against Pluto that borders on the irrational. Sorry, Dr. Brown, but you cannot "kill" a planet by deciding to change what you call it. Pluto is very much out there, the same as it always has been. The debate over the definition of the word "planet" and over Pluto's status is far from over. Meanwhile, I would expect a far more professional, rational attitude from someone of Dr. Brown's status.
Posted by: PhilCo126 Oct 14 2006, 12:59 PM
Don't know if anybody brought this up yet ...
But ...
Does the UMSF logo on the top left of the page needs any adjustment ?
Posted by: djellison Oct 14 2006, 01:19 PM
It's been mentioned before
If someone goes and changes the logo on the plaque on the Pioneer spacecraft....then I'll change the logo
Doug
Posted by: PhilCo126 Oct 14 2006, 02:12 PM
Great thinking Doug ... back in 2004, Pluto was still considered a planet ...
Posted by: Alan Stern Oct 14 2006, 10:45 PM
Pluto is a planet and perhaps the most historic object discoverd of the past 150 years in solar system science.
-Alan
Posted by: GregM Oct 15 2006, 05:29 PM
.
Posted by: helvick Oct 15 2006, 06:01 PM
I find most of your arguments very well founded and your position is clearly one of the calmer ones in this debate but this last item doesn't make much sense. Why not 20 planets if needs be? There are certainly many more than 20 planets provided we don't limit ourselves to our Solar System so why not have 20 or more here? I'll accept that it doesn't make much sense to include most "satellites" in the same bucket as most "planets" but in my book Titan (as an entity in itself) has much more in common with Venus and Earth than it does with our Moon so why arbitrarily lump it into a group that would imply that it was other than it is?
Posted by: Jyril Oct 15 2006, 06:35 PM
Why some objects that clearly belong to debris belts should be considered planets? If only some of them, then why not all?
If Pluto is considered a planet, any remotely meaningful definition would mean dozens of planets. When asked, "Should Pluto be demoted?" most people said "no" but if asked "Should there be dozens of planets?" the answer would have been "no" again. Of all potential definitions, the "leave no iceball behind" definition was the least popular.
Like it is already said several times before, the whole term 'planet' is dumb. There is no good definition that is both scientific (i.e. not arbitrary) and exclusive. There is not much common between Jupiter and Earth; both are round, dominate their neighborhoods and have circular, low-inclined orbits. Still they both are 'planets'. Physically Earth is much more similar to the Galilean moons and Titan. Titan, a would-be planet, and Atlas, a tiny chunk of ice, are both just 'Saturnian satellites'.
I think the best thing to do is to ditch history and culture-loaded terms like 'planet' and classify objects by their physical properties and orbital properties separately.
Posted by: helvick Oct 15 2006, 07:01 PM
Yep - leave "planet" as a cultural term that is decided by common use and get the IAU to come up with a sensible classfication for all bodies within all solar systems and then map our bodies into that. Such a system should be of some _use_ in defining the broad physical characteristics and dynamics of the bodies. Ideally in my book it would be represented by an unpronouncable "word" so we could forever prevent a repeat of the spurious arguments based as the confusion of schoolchldren and society's attachment to a scientific definition that become obsolete.
Posted by: David Oct 15 2006, 08:19 PM
Those who have a historical interest in the question of the definition of a planet, may be interested in reading a discussion of the same written by William Herschel shortly after the discovery of Ceres and Pallas (1802), at which time these bodies are rejected as potential planets, and it is suggested that they require a new name, neither planet or comet, for which the name asteroid is proposed: the intention being that "planets, asteroids, and comets, will in future comprehend all the primary celestial bodies that either remain with, or only occasionally visit, our solar system."
Observations on the two lately discovered celestial Bodies
http://links.jstor.org/sici?sici=0365-5695%281800%2F1814%291%3C80%3AOOTTLD%3E2.0.CO%3B2-D
http://links.jstor.org/sici?sici=0261-0523%281802%2992%3C213%3AOOTTLD%3E2.0.CO%3B2-R
See especially pp. 223 of the article et seq.
The criteria Herschel uses for his definition of planet very nearly anticipate all the definitions that have been suggested since. They are, verbatim:
1. They are celestial bodies, of a certain very considerable size.
2. They move in not very excentric [sic] ellipses round the sun.
3. The planes of their orbits do not deviate many degrees from the plane of the earth's orbit.
4. Their motion is direct. (Herschel means "prograde")
5. They may have satellites, or rings.
6. They have an atmosphere of considerable extent, which however bears hardly any sensible proportion to their diameters.
7. Their orbits are at certain considerable distances from each other.
It would seem there is nothing new around, as well as under, the Sun.
In applying his criteria, Herschel finds that the asteroids differ from the planets in criteria 1, 3, 5 (incorrectly, as it turns out; he assumed that no body as small as an asteroid could have a satellite), and 7, and agreed in 2 (he was unaware of the more eccentric asteroids) and 4. On 6 he was really aiming at distinguishing planets and asteroids from comets (interpreting the "coma" of the comet as an atmosphere). His "7", is basically the "orbit clearing" idea expressed in a somewhat different way; though he seems to have had Bode's Law in the back of his mind, saying that allowing two "planets" in crossing orbits would upset the regular arrangement of planetary orbits, whereas it could be retained if they were placed into a "different species".
Applying Herschel's criteria to Pluto and Eris, we find the following responses:
1. Unknown, because we do not know where to draw a line in the large gap between Mercury and Ceres.
2. May exclude Pluto, certainly excludes Eris.
3. Excludes Pluto and Eris.
4. Includes Pluto and Eris.
5. Includes Pluto and Eris.
6. Includes Pluto, Eris?
7. Excludes Pluto. probably excludes Eris too.
So whereas by Herschel's criteria, asteroids might meet from 1 to 3 planetary criteria, Eris and Pluto meet three or four.
Posted by: Kevin Heider Oct 15 2006, 09:05 PM
-Alan
Why do dynamically challenged KBOs get all the respect and glory? Perhaps this is the reason I hope that Ceres is still considered an asteroid. Ceres orbits in the asteroid belt, is a member of the asteroid belt, and should be known as an asteroid AND a 'dwarf planet'.
Ceres apparently lives in the ghetto of the solar system and just because it is now a 'dwarf planet' let's hope that people don't forget where it comes from! If Ceres is not an asteroid then smaller asteroids will truly never get any public respect.
Asteroids like (152) Atala (100+km in dia; low albedo and a featureless reddish electromagnetic spectrum) deserve to be part of something bigger, ie: a group of objects that include (1) Ceres.
-- Kevin Heider
Posted by: David Oct 16 2006, 03:46 AM
I should add that Herschel had a less-than-noble reason for opposing the admission of Ceres and Pallas as planets in 1802; if they were planets, then his discovery of the "Georgian Planet" (Uranus) only 21 years earlier would shine a little less lustrously.
But I prefer to absolve him of such a motive; it appears from his writing that his gut objections were aesthetic: these tiny asteroids -- thought there were then only two of them, but Herschel, with laudable prescience, foresaw that many more would be discovered -- were making his solar system untidy. Herschel's distress at the messiness of the asteroids mirrors exactly modern astronomers' distress at the messiness of the KBOs.
In addition to attempting to define the term planet, Herschel also provides a definition of asteroid (a term that he seems to have invented), which he intended to be "sufficiently extensive to take in future discoveries". It is as follows:
"Asteroids are celestial bodies, which move in orbits either of little or of considerable excentricity [sic] round the sun, the plane of which may be inclined to the ecliptic in any angle whatsoever. Their motion may be direct, or retrograde; and they may or may not have considerable atmospheres, very small comas, disks, or nuclei."
(Herschel's instruments had misled him into perceiving Ceres and Pallas as having faint comae surrounding them.)
It would appear that if Herschel had still been alive in 1930, and had not changed his mind, he would likely have classified Pluto as an asteroid, and would certainly have considered the other KBOs to be asteroids as well.
Posted by: Gsnorgathon Oct 16 2006, 07:23 AM
C'mon guys! There are five planets: Mercury, Venus, Mars, Jupiter, and Saturn. The rest of 'em are - I dunno quite what - poseurs? - but they ain't planets.
Posted by: Jyril Oct 16 2006, 08:22 AM
If you think that way, you should accept the Sun and the Moon as planets.
Posted by: Alan Stern Oct 16 2006, 09:02 AM
Now we are relying on the perspectives of a man living two centuries ago to justify a bad definition
of planets?
With all due respect, I am disappointed by the discussion above. It is as if, owing to the diveristy of life, one concluded there is no common thread to living things, no tree of life with all its diversity, so we might as well simplify by just defining organisms as objects which control their ecological niche.
Yes, planets are diverse, but they do make up a class of bodies larger than rocks and smaller than stars.
They are found in many dynamical niches, colors, compositions, and sizes, but they all share the traits
that they neither do fusion in their interiors as stars do, nor retain arbitrary shapes, as rocks do.
-Alan
Posted by: JRehling Oct 16 2006, 01:48 PM
[quote name='GregM' date='Oct 15 2006, 10:29 AM' post='72675']
I find it absolutely remarkable that a group of science minded people (people who often relegate the “human” aspect of “science” behind that of logic, facts, measurements, and figures) are now placing those “human aspects” as reasoning to resist this decision.
[/quote]
It's a mistake to think that this planet-definition issue has anything to do with science.
Objects in space are often the subject of scientific investigation. That doesn't mean that every human endeavor pertaining to them is science. This is a good example of one that isn't.
If someone tried to figure out if Pluto was at sometime in the past a satellite of Neptune and they set about collecting data and testing models... that would be science: an investigation to determine something about reality.
2006's planet-definition debate has not involved any questions whatsoever about the inherent nature of things. It's more of an aesthetic debate. It isn't science any more than the contest to name the MER rovers was science.
[quote name='GregM' date='Oct 15 2006, 10:29 AM' post='72675']
Tell you what: since the books that I have on my shelf say that Jupiter has only 12, and from my sentimental historical perspective I feel more comfortable with that idea, I move that the remaining objects orbiting Jupiter not be considered moons.
[/quote]
If there were a significant "line" to draw between #12 and #13, you might have something there. By and large, I think the ongoing discoveries have trickled in over the years, although chronological gaps without discoveries have surely come and gone. There is a highly significant line between #4 and #5, and we do have a name to reflect that, crediting the discoverer.
The notion of defining planet is almost as silly as it would be to define Galilean in case Jupiter turned out to have a large previously-undiscovered satellite (sure, it would have to be very dark and of very low density) to see if it should be called a Galilean. Or to draw a line between Io and Europa and say that the fourth-largest of them isn't truly a Galilean because it is too much smaller than Ganymede. Impossible: the term Galilean is purely historical. There are four of them and that can never change. New measurements cannot possibly be brought to bear on the matter.
Nobody's convinced me that the term "planet" isn't similar. How would they convince me -- by fiat?
[quote name='GregM' date='Oct 15 2006, 10:29 AM' post='72675']
Adjust to reality guys.
[/quote]
Nobody's anti-reality, but we are trying to decide which constraints to apply in this aesthetic, non-scientific endeavor.
For me, reality includes the observation that "river" has no formal definition, people write scientific papers using the word "river" without apparent difficulty, and people interact daily with rivers without apparent difficulty. I grew up near a stream about ten feet wide that people (and maps) call "Center Run". Is it a river? I don't think many people would say so, although if you polled enough people someone eventually would. Do we need a committee to define standards of riverhood? I haven't yet seen a problem that that would solve.
And "planet" is no different except very few people ever interact with the objects past Saturn, whereas thousands of people drive cars on bridges over Center Run every day.
[quote name='GregM' date='Oct 15 2006, 10:29 AM' post='72675']
Pluto isn’t what it was originally thought to be. That doesn’t make it insignificant, just different than our traditional viewpoint. Some people feel that adjusting viewpoints to better fit observation is somehow degrading poor Pluto.
[/quote]
Pluto isn't what it was thought to be in 1965, but as far as this debate goes, it's much the same as our knowledge of it in 1979 -- excepting that it's also a bit more "planetlike" in having three satellites instead of one and a dynamic atmosphere.
The real thing that's changed is that in 1965, it was believed that the largest nonplanet orbiting the Sun was 19% the size of the smallest planet. Now it is certain that no such gap exists in the distribution of sizes. The biggest wake-up call that reality has handed us is that there is no natural category of planet (vs things in the next size bracket down -- there is no size bracket!).
[quote name='GregM' date='Oct 15 2006, 10:29 AM' post='72675']
From the broadest perspective, to say that Pluto is in the same league as Saturn or even Mars is in my mind being just a little delusional.
[/quote]
From the broadest perspective, to say that Mars belongs more in the category of Saturn rather than Pluto is flagrantly off.
Mars is 1/17th the size of Saturn... and 2.9 times the size of Pluto.
[quote name='GregM' date='Oct 15 2006, 10:29 AM' post='72675']
Maybe the new definitions are not perfect - or even that good for that matter, but at least there is an attempt being made to recognise that newly understood diversity and complexity in the Solar System – instead of hanging dogmatically onto a outdated perspective.
[/quote]
Actually, this is the worst kind of dogmatic hanging-on: the failure to recognize that "planet" is not a natural category and the delusion that it lends itself to formal definition. River-scientists have no such delusion.
What came before 2006 was not delusion (except, of course, when Pluto was assumed, without evidence to be so large). "Planet" was a know-it-when-you-see-it category. That is precisely what the evidence in nature supports: there simply is no gap or natural property distinguishing Jupiter and Mercury on the one hand from Ceres on the other. Jupiter and Mercury are lumped into a category that excludes Ceres for one reason only: history. Calling it science and trying to reverse-engineer it into being reasonable is absurd.
Posted by: AndyG Oct 16 2006, 01:52 PM
Alan's "planet" definition is too broad a range for me, and the IAU decisions are...weird. Imagine the post-IAU Empire Strikes Back:
Darth Vader: Small solar system body fields do not concern me, Admiral. I want that ship, not excuses.
Admiral Piett: Sorry, Lord Vader. When I said small solar system body field I meant a field, which is actually quite big, full of small solar system bodies. And, it has to be said, one or two dwarf planets.
Darth Vader: How small?
Admiral Piett: The field, the bodies or the dwarf planets?
Darth Vader: Never underestimate the power of this farce!
Admiral Piett (choking): Many <gasp> could be classified as dwarf planets - they have clear signs of <gulp> hydrostatic equilibrium, but none have yet <gurgle> cleared their neighbourhoods...
...Ah, how simple our lives were in 1980, when we knew what an asteroid was.
Andy G
Posted by: David Oct 16 2006, 03:19 PM
of planets?
I think a better word than "rely on" is "take into account". As Herschel seems to have been the first, or at any rate one of the first, to propose a scientific definition (good or bad) of planet as distinct from other types of solar system bodies, his analysis may serve as a kind of baseline for comparison. Of course, to properly understand the uses and meanings of the word "planet" over the last 204 years, there should really be an exhaustive search of the literature, scientific and popular, to see what definitions have been proposed and how they have been used. To the best of my knowledge, this was not and has not been done by either the Oligoplanetists or the Plioplanetists, a circumstance which I consider very unfortunate, because it means that neither side can put their positions in historical perspective. It's all very well to come up with a "scientific" division of solar system bodies, but to attach that definition to the world "planet" without first thoroughly considering what the word has meant and does mean to different populations is foolish. If a drastic break from the historical meaning of "planet" is contemplated, it should at least be done with full knowledge and open admission that such is being done.
Posted by: MahFL Oct 20 2006, 11:42 AM
I attended a meeting to discus if Pluto was a planet or not in the International Space Musuem on Second Life, it was fascinating. I think the consenses was NO.
Posted by: Greg Hullender Oct 21 2006, 04:26 AM
It's nice to find something I think we can all agree on. I too believe that Pluto is not located in the International Space Museum on Second Life, and if it were, it would definitely NOT be a planet. :-)
Posted by: laurele Oct 21 2006, 10:02 PM
Just what is it that "we can all agree on"? Are you referring to Pluto being located in the museum display or whether it should be located with the other planets? If it's the latter, back to the issue of whether Pluto should be classified as a planet, there is far from consensus on the issue. I for one along with many others believe Pluto should be included.
Posted by: JRehling Oct 23 2006, 02:30 AM
I think he's referring to Pluto itself not being located in the museum -- a joke based on a misplaced modifier in the text he quoted.
FWIW, last week, I visited the Bay Discovery Museum just north of the Golden Gate Bridge and they had a wall painted with the images of nine planets, though the artwork took liberties with the appearances of all of them and none of them came bearing names.
Posted by: Bob Shaw Jan 25 2007, 11:08 PM
From Our Special Correspondent:
http://pr.caltech.edu/periodicals/EandS/articles/LXIX4/funeral.html
Bob Shaw
Posted by: AlexBlackwell Jan 25 2007, 11:14 PM
http://pr.caltech.edu/periodicals/EandS/articles/LXIX4/funeral.html
Bob Shaw
Thanks, but I didn't need a "Special Correspondent," whoever that is, to point out this issue of E&S. I relied on one of our http://www.unmannedspaceflight.com/index.php?showuser=7, who http://www.unmannedspaceflight.com/index.php?s=&showtopic=3802&view=findpost&p=81550 it earlier.
Posted by: Bob Shaw Jan 25 2007, 11:19 PM
Alex:
The parade sounds like a lot of fun! I particularly like the idea of synchronised invisible men.
http://asymptotia.com/2006/11/22/some-things-i-like-about-the-doo-dah-parade-i/
Bob Shaw
Posted by: laurele Jan 26 2007, 05:34 AM
"One of the mourners, Caltech Image Processing and Analysis Center staff engineer Kaly Rengarajan, saw the event as a way to educate the public. “The very idea of Pluto being demoted is so exciting. We’re trying to refine what we knew before. I’m so glad people are being made aware!” she raved."
This event may be entertaining, but I wouldn't take it seriously as "something to make people aware" of "refining what we know." Holding a "funeral" for Pluto is premature. Pluto is not dead. An event like this may generate media attention, but one is hard pressed to view it as educational or as a means of stimulating thought. The fact is, this is still an open debate with two sides. The Doo Dah parade may end up having to hold a "rebirth" ceremony for Pluto's restoration to planethood in the near future.
Posted by: Bob Shaw Jan 26 2007, 11:55 AM
I'm sure they'd do just that - a baby Pluto (with a Mickey Doll beside it) and it's sibling moons in the arms of Mother Sol, her family of uncles, aunts and cousins dancing around... ...I can see it already!
I just hope the Claude Rains Squad don't spoil the view!
Bob Shaw
Posted by: mchan Jan 27 2007, 03:45 AM
They have letters of transit.
Posted by: doctorclu Jun 18 2007, 02:09 PM
Sorry, I know this is an old message but thought it hilarious!
Posted by: nprev Jun 18 2007, 02:20 PM
Funny, yes, but argh...PLEASE no more planet definition debates, please please please...my stomach lining's still recovering from all the aspirin I took last time to stop the pounding migraines...
Posted by: djellison Jun 18 2007, 03:50 PM
Don't worry - it's not going to happen here.
Doug
Posted by: alan Jun 21 2007, 10:08 PM
The topic title reminds me of a alternative slide Mike Brown slipped into one of his presentations (the details of which I won't discuss out of sympathy for nprev's stomach lining)
"How I killed Pluto and why it had it coming."
Posted by: nprev Jun 22 2007, 03:11 AM
Thanks, Alan...<eats some Tums>...no sweat, just a little indigestion!
Oddly enough, my ex expressed sentiments similar to that title...
Posted by: jaredGalen Jul 10 2007, 11:30 AM
Poor pluto
http://www.mathiaspedersen.com/3dportfolio_poor_pluto_high.html
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