PDA

View Full Version : Definition of 'Planet' Expected in September



ToSeek
2006-Jun-08, 06:29 PM
Definition of 'Planet' Expected in September (http://www.space.com/scienceastronomy/060608_planet_definition.html)


Historians and educators have joined astronomers in an effort to break a deadlock on contentious discussions over a definition for the word planet.

A decision is expected in September, but history suggests rewriting the textbooks could be more challenging than finding tiny new worlds at the edge of the solar system.

The International Astronomical Union (IAU) is expected to propose wording to delineate planets from other small, round objects at its 12-day General Assembly meeting in Prague this August. The proposal will be based on recommendations from a newly formed committee that includes experts outside the realm of astronomy tasked to break a deadlock in earlier committee discussions.

Depending on the outcome of a separate controversial procedural issue—whether IAU members should be allowed to vote on such things—astronomers might then have the chance to weigh in on the definition later in the same meeting, SPACE.com has learned.

If approved, the definition would then be announced in September.

furtim
2006-Jun-09, 02:00 AM
Yikes. This one is gonna be bloody, but I think we'll be better off once we have a firm definition from a relatively authoritative body... that we can then debate about and second-guess. ;) But at least it's a solid start and ought to put us in a better position than simply arguing from tradition.

Ken G
2006-Jun-09, 04:26 AM
What I find interesting is the idea to bring in "experts" (in what?) from outside astronomy to "break the deadlock" (!). Like they think that if astronomers can't agree, it must be because they have too much knowledge-- let's bring some people in who don't know planets from a hole in the wall, they will know how to define one. I'd like to be a fly on the wall when the media consultants are brought in... "our research shows that people don't really understand gravity or the internal physics of large objects, so we don't want to use anything happening inside the planet as a defining factor. It's all getting too complicated, people are tuning out. Why don't we just define them as the ones people can see with their own eyes on a dark night?"

Ara Pacis
2006-Jun-09, 06:57 AM
I think Ken G's post exemplifies why outsiders are needed. I expect they are consulting with communications experts and linguists. After all, words and definitions fall under their expertise. Educators might be helpful since their classes are where the rubber meets the road in establishing a new definition. If education does not take to the new definition then the IAU will have to argue it again sometime in the future when future astronomers want a better definition. Historians, on the other hand, will probably only serve to give certain astronomers the privilage of saying "told you so."

HenrikOlsen
2006-Jun-09, 11:37 AM
As long as the "experts" brought in aren't astrologers I'm ok with it.

Rivertree
2006-Jun-09, 11:44 AM
I predict that the Earth is considered a planet. Furthermore, the Moon may be considered a moon. This is open to some debate as the Earth/Moon may be considered as a binary system.

Meanwhile, the Pluto/Charon binary system usually gets picked on. Alone neither seems worthy of planet status. However, together they pretty much make a "planet."

Ken G
2006-Jun-09, 01:22 PM
Historians, on the other hand, will probably only serve to give certain astronomers the privilage of saying "told you so."
I'l reserve my "told you so" until we see the fruits of the "communications experts" in this endeavor.

Rivertree
2006-Jun-15, 04:02 AM
http://hubblesite.org/reference_desk/faq/answer.php.id=5&cat=solarsystem

FULL TEXT

How many planets are there in our solar system?

"Our solar system officially has nine planets and one star: the Sun. In order from the Sun out, the planets are: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune and Pluto. The discovery of an object larger than Pluto in 2005 rekindled the debate over whether such objects, belonging to the "Kuiper Belt" -- a collection of icy bodies located beyond Neptune-- should be called planets. Pluto itself belongs to the Kuiper Belt."

10th Planet
http://www.cnn.com/2006/TECH/space/02/01/tenth.planet/
"The claims of a 10th planet have re-ignited a debate over just how many objects should be called planets -- there is no official definition."
. . . .
"It can't get an official name until it has an official status and right now it doesn't have an official status, so it can't get a name," he said.
-------------------------------------------------------
You be three one three has a nice ring to it.

Rivertree
2006-Jun-15, 04:04 AM
I don't mean a ring as in Saturn has nice ring to it.

ToSeek
2006-Jun-21, 08:02 PM
Pluto Could Lose Planet Status (http://www.physorg.com/news70120085.html)


At its conference this August, the International Astronomical Union (IAU) will make a decision that could see Pluto lose its status as a planet.

hhEb09'1
2006-Jun-21, 08:28 PM
Pluto Could Lose Planet Status (http://www.physorg.com/news70120085.html)Actually, although that linked article is titled "Pluto Could Lose Planet Status", the only specific definition of a planet that it discusses would leave Pluto as a planet (albeit, induct eleven more).

Ara Pacis
2006-Jun-21, 08:51 PM
Sounds like her proposal is what I and a lot of people were suggesting in my "what is a planet?" definition debate thread.

hhEb09'1
2006-Jun-21, 08:53 PM
Who is her?

Ara Pacis
2006-Jun-21, 09:03 PM
Oops, I saw Marc Buie and somehow I read it as Marcie.

Saluki
2006-Jun-21, 09:21 PM
Wouldn't it make sense to wait on the NH flyby to make a definitive pronouncement on the Pluto question? Surely we will have far better information at that point. It seems that if they come out in September and say that Pluto is not a planet, it would be difficult to reverse the decision if NH turned up something that made Pluto more "planetlike", whatever that means.

Peter Wilson
2006-Jun-21, 11:16 PM
What I find interesting is the idea to bring in "experts" (in what?) from outside astronomy to "break the deadlock" (!). Like...let's bring some people in who don't know planets from a hole in the wall, they will know how to define one. They could have done a lot worse. They could have called for congressional hearings.

Ken G
2006-Jun-22, 02:32 AM
Lol-- there's still time for that. Or, they could leave it up to the individual school boards!

Ara Pacis
2006-Jun-22, 03:27 AM
Or they could leave it to Holst.

yuzuha
2006-Jun-22, 08:16 AM
Far as I'm concerned a planet can be anything bigger than 1000km in diameter (or radius if you like bigger stuff) that directly orbits the sun.

antoniseb
2006-Jun-22, 11:22 AM
Far as I'm concerned a planet can be anything bigger than 1000km in diameter (or radius if you like bigger stuff) that directly orbits the sun.
As far as I'm concerned 'Planet' is just a word, and I'll use it in the common parlance, which wil certainly be influenced by whatever the IAU decides.

hhEb09'1
2006-Jun-22, 04:30 PM
Pluto Could Lose Planet Status (http://www.physorg.com/news70120085.html)Sticks has just linked (http://www.bautforum.com/showthread.php?p=767915#post767915
), indirectly, to another article about the same: Crunch time for Planet Pluto (http://news.bbc.co.uk/1/hi/sci/tech/5099292.stm), but it is a BBC article dated 6/20 and bylined. Your article is dated 6/21, but says its source was the BNSC. A lot of the wording is identical. Weird.

HenrikOlsen
2006-Jun-22, 05:21 PM
When you get similar wording in "independent" articles, they're probably lifted straight out of the same press release. :)

hhEb09'1
2006-Jun-22, 05:24 PM
When you get similar wording in "independent" articles, they're probably lifted straight out of the same press release. :)O sure. But is it common to byline those?

Ara Pacis
2006-Jun-22, 05:27 PM
Maybe if you are Jason Blair or Stephen Glass...

ToSeek
2006-Jun-22, 06:24 PM
I would guess that Physorg printed the release straight, and BBC News (Nicola Cook) took it and expanded on it. The latter seems a little morally dubious, though.

Randall Cameron
2006-Jun-26, 11:06 AM
Tradition! Hard to break old habits, even for the IAU.

Personally, I think Pluto should be classified as a KBO, since its characteristics (small, icy, highly eccentric and out of plane orbit) put it solidly in that category. "Planet" should be formally defined to include only rocky or gas giant bodies with near circular, in-plane, primary solar orbits, of sufficient size to be gravitationally compressed into roughly spherical form. Mercury should roughly define the baseline for maximum eccentricity, although size could certainly go lower.

Under that definition, Earth - Moon might be a double planet. None of the large gas giant satellites would qualify, because they primarily orbit their (vastly more massive) planets, not the sun. Earth and Moon have an unusual co-orbital relationship because of their relatively similar size, plus the fact that Earth does not have any other satellites of its own.

I would be interested in hearing other opinions from this community, including definitions of planet that might include Pluto.

ciderman
2006-Jun-26, 01:14 PM
I guess any definition should also include planets around other stars, many of which have high eccentricities.
Hmm, binary stars/brown dwarves might produce even more confusion:)

Ken G
2006-Jun-26, 02:32 PM
Note also that what this thread is really about is "major planets'. The most general astronomical meaning for the word "planet" that is used in practice includes moons of other planets, as well it should.

hhEb09'1
2006-Jun-26, 04:43 PM
Mercury should roughly define the baseline for maximum eccentricity, although size could certainly go lower. That's it! Mercury is not a planet, it's a moon of the Sun. :)

Ara Pacis
2006-Jun-26, 06:16 PM
Randall could start yet another planet definition debate thread. It's been a few weeks since we had a big brouhaha.

George
2006-Jun-26, 07:57 PM
Didn't the IAU drop Pluto from planetary status once already? [My googling fails to find the reference.] IIRC, there was an outcry about it and they reinstated it, or something like that.

hhEb09'1
2006-Jun-26, 08:05 PM
Didn't the IAU drop Pluto from planetary status once already? [My googling fails to find the reference.] IIRC, there was an outcry about it and they reinstated it, or something like that.Nope. A museum gave the issue a bunch of publicity, and one of the guys brought the issue up, but it was sent back to committee.

George
2006-Jun-26, 08:57 PM
Nope. A museum gave the issue a bunch of publicity, and one of the guys brought the issue up, but it was sent back to committee.
Ah, it never got out of committee, then. That sorta rings a bell.

However, you're not, perhaps, referring to the NY's American Museum of Natural History event which left Pluto out of its planetary display (http://www.scienceclarified.com/dispute/Vol-1/Is-Pluto-a-planet.html)?....

...in year 2000 the Rose Center for Earth and Science at New York City's American Museum of Natural History put up an exhibit of the solar system leaving out Pluto. That action received press coverage and re-ignited the controversy.

hhEb09'1
2006-Jun-27, 03:19 AM
However, you're not, perhaps, referring to the NY's American Museum of Natural History event which left Pluto out of its planetary display (http://www.scienceclarified.com/dispute/Vol-1/Is-Pluto-a-planet.html)?....Why not? :)

Maksutov
2006-Jun-27, 05:00 AM
Or they could leave it to Holst.True. That would bring us back to seven, plus Earth, astrologically speaking.

The real resolution of this whole mess would be to classify Pluto as a dog.

http://img236.imageshack.us/img236/6100/pluto4pi.th.gif (http://img236.imageshack.us/my.php?image=pluto4pi.gif)

Ken G
2006-Jun-27, 12:28 PM
I think Pluto's days as a major planet are numbered, but it will always be considered a planet in a more general sense. As I've said before, I would stress the importance of defining a planet purely in terms of its own internal physics, the way everything else in astronomy is defined and for good reason. But if people want to debate all kinds of happenstance requirements (like orbital properties or conceptually arbitrary size limits), let them confine that to the term 'major planet', which is essentially a pop culture debate.

George
2006-Jun-27, 12:50 PM
Why not? :)
Because, somehow, I thought a group found out the IAU, some years ago, was going to demote Pluto and this group argued, and won, Pluto's reinstatement. Obviously, if true, it would not have been the museum :). It appears I have the story wrong, but I haven't researched it enough to know how I got the idea in the first place.

George
2006-Jun-27, 03:22 PM
I think Pluto's days as a major planet are numbered, but it will always be considered a planet in a more general sense. As I've said before, I would stress the importance of defining a planet purely in terms of its own internal physics, the way everything else in astronomy is defined and for good reason. But if people want to debate all kinds of happenstance requirements (like orbital properties or conceptually arbitrary size limits), let them confine that to the term 'major planet', which is essentially a pop culture debate.
I suspect you're right.

If Pluto looses planethood, do you (ya'll) think a new term for Pluto may arise, even if a familiar one? [I would think they would almost have to give it a designation, else the issue would be left hanging.]
Might it be...(I hope this isn't too much replication of prior posts)
Planetoid
Minor Planet
MKBO (Massive Kuiper Belt Object)
MDO (Massive Disney Object, taking advantage of the potential naming transition (ie Pluto), [object must be larger than Epcot's 55m geosphere]) ;)
Pseudoplanet
Dwarf planet

homo_cosmosicus
2006-Jun-27, 03:33 PM
I suspect you're right.

If Pluto looses planethood, do you (ya'll) think a new term for Pluto may arise, even if a familiar one? [I would think they would almost have to give it a designation, else the issue would be left hanging.]
Might it be...(I hope this isn't too much replication of prior posts)
Planetoid
Minor Planet
MKBO (Massive Kuiper Belt Object)
MDO (Massive Disney Object, taking advantage of the potential naming transition (ie Pluto), [object must be larger than Epcot's 55m geosphere]) ;)
Pseudoplanet
Dwarf planet

Planetiod, or MKBO.

But I would prefer - Kuperoid.

Ara Pacis
2006-Jun-28, 01:32 AM
Quasi-planets
Hothites?

I still think that characteristics like orbital elements and composition are better used to determine sub-categories of planet

Ian R
2006-Jun-28, 03:24 AM
Since 'planet' isn't a scientific term anyway, why don't we just give it an arbitary definition (anything equal or over the size of Pluto), and let the scientists use their own terms (gas giants, terrestrials, KBOs, asteroids, etc.).

You can't say that a KBO can't also be a planet - what if such an object equal or larger than Mercury was found? Obviously in this instance, the astronomers would call it yet another KBO, but by popular parlance, it would become a new planet.

Ian.

yuzuha
2006-Jun-28, 06:59 AM
I sort of like the definition that a planet as an object of sufficient mass to be gravitationally crushed into spherical shape, yet too small to initiate fusion reactions, whose primary orbit is around a stellar object.

jkmccrann
2006-Jun-28, 08:43 AM
Whatever their decision in September, I frankly doubt that'll be the end of it. No doubt arguments will flare up around the time, and then die down to await the discovery of any new objects that may contravene whatever definition they come up with.

Just hope they don't try and gradnfather Pluto and exclude other KBOs, that would really be a pathetic response and ultimately lead to more trouble down the line.

hhEb09'1
2006-Jun-28, 09:53 AM
Just hope they don't try and gradnfather Pluto and exclude other KBOs, that would really be a pathetic response and ultimately lead to more trouble down the line.Maybe they could include Pluto and exclude all other Trans Neptunian Objects, because Pluto got his ticket punched twenty years ago.

George
2006-Jun-28, 03:48 PM
Maybe they could include Pluto and exclude all other Trans Neptunian Objects, because Pluto got his ticket punched twenty years ago. I agree with this idea. Pluto does not deserve demotion; it's family now. How many "stars" have been demoted? Perhaps the subclasses should be the greater issue.

Bynaus
2006-Jun-28, 05:03 PM
I sort of like the definition that a planet as an object of sufficient mass to be gravitationally crushed into spherical shape, yet too small to initiate fusion reactions, whose primary orbit is around a stellar object.

I would add a population criterion to this: A planet has to dominate the objects on his orbit gravitationally - if not, it is a planetoid, not a planet. This makes Ceres, Vesta, Pluto etc. planetoids.

hhEb09'1
2006-Jun-28, 05:26 PM
I would add a population criterion to this: A planet has to dominate the objects on his orbit gravitationally - if not, it is a planetoid, not a planet. This makes Ceres, Vesta, Pluto etc. planetoids.What objects are you including in Pluto's orbit?

Bynaus
2006-Jun-28, 09:15 PM
What objects are you including in Pluto's orbit?

The Plutinos and lots of KBOs on Pluto-crossing orbits. Look at Earth, Mars, Jupiter - they all concentrate the majority of the matter on their orbits, by several orders of magnitude. With Pluto, Vesta, Ceres, it is obviously very different.

I say (I propose... ;) ), together with spherical shape and no fusion reactions, this defines a planet.

Ara Pacis
2006-Jun-28, 09:37 PM
I would add a population criterion to this: A planet has to dominate the objects on his orbit gravitationally - if not, it is a planetoid, not a planet. This makes Ceres, Vesta, Pluto etc. planetoids.

But then you have to decide where those limits on orbital parameters are and why they are not arbitrary.

Wolf-S
2006-Jun-28, 09:44 PM
I've been a fan of dominant orbit thing (8 planets - Pluto excluded), but maybe having many planets isn't so bad after all? Considering planet any object that is spherical by its gravity (how many of these are there?), the following sentences look quite good:

"Our Solar system consists of ~50 (whatever the number is) small and big planets."
"Pluto is one of the largest planets in the Kuiper belt."
"2003 UB313 is the largest known planet in the Kuiper belt."
"Ganymede is the largest planet around Jupiter/in Jovian system" (including spherical moons, and "Ganymede is the satellite/moon of Jupiter" would be equally valid, I think)
"The seven largest planets are Jupiter->Mars. They were once considered the only planets, along with Mercury and Pluto."

All smaller objects would be asteroids or planetoids.

Just some loud thoughts. I don't remember if the consequences of having many planets have been discussed before.

Ara Pacis
2006-Jun-29, 12:44 AM
Just some loud thoughts. I don't remember if the consequences of having many planets have been discussed before.

Human sacrifice, dogs and cats living together - mass hysteria.

yuzuha
2006-Jun-29, 02:23 AM
Human sacrifice, dogs and cats living together - mass hysteria.

Nah, a bunch of astrologers would have to hurry up and figure out what they do ^0^

Ara Pacis
2006-Jun-29, 03:41 AM
that was a quote from Ghostbusters

George
2006-Jun-29, 05:04 AM
Just curious... will there be any chance star classifications might change? The sun would be a yellow dwarf, if it were yellow and if it were a dwarf, but it's not yellow and all the M class stars are making the sun look a lot bigger on average. [Now I'm a trouble maker ;)]

Ken G
2006-Jun-29, 12:09 PM
Don't hold your breath, traditions die hard. If we changed stellar classifications, we might have to go ahead and rename all the designations that were invented before we knew what they were, i.e., half of astronomy...

NEOWatcher
2006-Jun-29, 12:24 PM
Don't hold your breath, traditions die hard. If we changed stellar classifications, we might have to go ahead and rename all the designations that were invented before we knew what they were, i.e., half of astronomy...
Just get out your historical Astro to IAU berlitz book.:shifty:

George
2006-Jun-29, 01:53 PM
Don't hold your breath, traditions die hard. If we changed stellar classifications, we might have to go ahead and rename all the designations that were invented before we knew what they were, i.e., half of astronomy...
:), a taxing task for taxonomists, apparently; I had only thought of our nearest star's classification. Is it really that bad?

Perhaps this will cut Pluto a little slack, though I wouldn't bet on it.

Nevertheless, a thought arose...
A Pluto by any other definition, is still a planet to me. [hmmm...almost works.]

jkmccrann
2006-Jul-08, 04:11 AM
Just curious... will there be any chance star classifications might change? The sun would be a yellow dwarf, if it were yellow and if it were a dwarf, but it's not yellow and all the M class stars are making the sun look a lot bigger on average. [Now I'm a trouble maker ;)]

One thing star-classification - and any putative changes to it don't have to worry about though is a public outcry. Statistically, probably 100% of the population would just assume that all the stars they see in the sky are pretty much identical to our own Sun.

Of course they're not, but there's definitely not the same level of attachment to any particular star-classification scheme as there is to the current public understanding of Pluto's status as a planet.

Any changes to the star-classification system would purely be a debate for the astronomical community to undertake and would create barely a ripple in the broader community.

If its warranted - and given my lack of knowledge I have no idea if it is, then the whole star-classification system should indeed be overhauled - maybe those of you with an interest in the area could draw up an overhaul?

loglo
2006-Jul-08, 04:48 AM
One thing that has puzzled me..is the general non-astro public really concerned about Pluto being a planet? All they have ever seen of it is a blurry blob in photos so why care one way or another? Given that they are pretty much taking the word of astronomers that a planet is there in the first place does it make any difference to be told that it isn't a planet after all? If there really is concern is it a US-centric Disney thing.... "Pluto not a planet, better not tell Mickey!" or is it a case of genuine interest? Frankly none of my non-astro friends in Australia have even heard of the debate.

IMHO.. think the whole issue is just being over-hyped. Frankly I couldn't care less what it is called. Is this a shocking attitude or am I getting hornery in my old age?

Ara Pacis
2006-Jul-08, 04:58 AM
One thing star-classification - and any putative changes to it don't have to worry about though is a public outcry. Statistically, probably 100% of the population would just assume that all the stars they see in the sky are pretty much identical to our own Sun.

Of course they're not, but there's definitely not the same level of attachment to any particular star-classification scheme as there is to the current public understanding of Pluto's status as a planet.

Any changes to the star-classification system would purely be a debate for the astronomical community to undertake and would create barely a ripple in the broader community.

If its warranted - and given my lack of knowledge I have no idea if it is, then the whole star-classification system should indeed be overhauled - maybe those of you with an interest in the area could draw up an overhaul?

You mean you never heard of the Politically Correct attempt to change G-class to P-class so that the mnemonic is "Oh, be a fine person, kiss me!" Of course this lead to another debate about Sol being a P-class star and whether or not its color was yellow.

George
2006-Jul-08, 04:04 PM
Of course they're not, but there's definitely not the same level of attachment to any particular star-classification scheme as there is to the current public understanding of Pluto's status as a planet.
Yes, quite true, no one has aspirations of seeing their grandkids move to another star. Planets offer hope for a greater future.


Given that they are pretty much taking the word of astronomers that a planet is there in the first place does it make any difference to be told that it isn't a planet after all? If there really is concern is it a US-centric Disney thing...
Is Pluto's planethood more of a U.S. thing? I hadn't thought of that. It is the only one discovered from over here.

parallaxicality
2006-Jul-08, 04:35 PM
One thing that has puzzled me..is the general non-astro public really concerned about Pluto being a planet? All they have ever seen of it is a blurry blob in photos so why care one way or another? Given that they are pretty much taking the word of astronomers that a planet is there in the first place does it make any difference to be told that it isn't a planet after all? If there really is concern is it a US-centric Disney thing.... "Pluto not a planet, better not tell Mickey!" or is it a case of genuine interest? Frankly none of my non-astro friends in Australia have even heard of the debate.

IMHO.. think the whole issue is just being over-hyped. Frankly I couldn't care less what it is called. Is this a shocking attitude or am I getting hornery in my old age?

Neill Tyson, the "bad guy" of the Pluto debate, says he's received mountains of hate-mail since officially de-listing Pluto as a planet in the Heyden Planetarium's gallery. As he said in Horizon's documentary a few weeks back, if astronomers were debating the demotion of Neptune, would there be a similar outcry? Probably not. This isn't being over-hyped. In 1999, when the IAU was first speculating on even the possibility of demoting Pluto, it was deluged with pleas to reconsider. Pluto means a great deal to the general public. There is, as Tyson says, something special about it. What is it? Hard to say. Pluto is the "last planet." It's far away, it's alien, it has a funny name (funny enough for a Disney dog to be named after it). Kids love it, probably because it's small and last on the list, so they identify with it. Also, it is the only planet discovered in living memory, which gives it an aura of scifi theremin cool that the more staid "older" planets don't have.

Kullat Nunu
2006-Jul-08, 09:20 PM
Non-astro public seems to be far more interested in the definition than astronomers themselves. If the definition was scientifically important, it would have been made long ago.

parallaxicality
2006-Jul-08, 09:27 PM
I would say, rather, that it wasn't scientifically important long ago. With the discovery of extrasolar planets and the Kuiper belt, it has become scientifically important in the last ten years.

hhEb09'1
2006-Jul-10, 02:40 PM
I would say, rather, that it wasn't scientifically important long ago. With the discovery of extrasolar planets and the Kuiper belt, it has become scientifically important in the last ten years.Classification schemes can often help in the advance of knowledge, but not at the level of an individual of a species. The classification of Pluto is not a scientific issue.

parallaxicality
2006-Jul-10, 04:14 PM
Well, as I hope my personal scheme for classifying planets demonstrated, I don't see this as merely an issue of Pluto's identity. It is far more complex than that. Pluto's identity does not change what it is or its scientific value, but the evolving comprehension of what a planet is or can be is of immense scientific importance