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Swift
2015-Nov-11, 03:57 PM
Will this bring peace to our planet (at least the planet CQ)?

From R&D magazine (http://www.rdmag.com/news/2015/11/new-method-defining-planets?et_cid=4934728&et_rid=54636800&type=headline)


At the 26th General Assembly for the International Astronomical Union, held in 2006, a new definition for a “planet” was introduced. It became defined “as a celestial body that is in orbit around the sun, has sufficient mass for its self-gravity to overcome rigid body forces so that it assume a hydrostatic equilibrium (nearly round) shape and has cleared the neighborhood around its orbit.”

This same meeting was also responsible for Pluto being stripped of its planetary status. The former ninth planet is now known as a dwarf planet.

Univ. of California, Los Angeles (UCLA) professor Jean-Luc Margot recently presented a simple test that will separate planets from other bodies, such as dwarf and minor planets.

He presented his new method at this week’s American Astronomical Society meeting.

According to Margot, the current system has created a “definitional limbo” for newly discovered bodies outside the solar system, as one of the prerequisites for a planet is that it orbits the sun. Exoplanets are left out of the definition entirely. According to NASA, close to 5,000 planetary bodies orbiting other stars have been discovered.

“One should not need a teleportation device to decide whether a newly discovered object is a planet,” said Margot, who teaches planetary astronomy.

Under the new approach, classification criteria would include the star’s mass, the planet’s mass and orbital period, all of which are attainable from Earth- or space-based telescopes, according to UCLA.

“When a body has sufficient mass to clear its orbital neighborhood, it also has sufficient mass to overcome material strength and pull itself into a nearly round shape,” Margot said.

According to UCLA, the test is easy to implement and could help classify 99% of the known exoplanets.

“The disparity between planets and non-planets is striking,” said Margot. “The sharp distinction suggests that there is a fundamental difference in how these bodies formed, and the mere act of classifying them reveals something profound about nature.”

When applied to the solar system, the test places the eight planets into a distinct category, and the dwarf planets—Pluto, Ceres and Eris—into another.

A paper regarding Margot’s proposal is forthcoming from the Astronomical Journal.

Centaur
2015-Nov-11, 05:14 PM
Will this bring peace to our planet (at least the planet CQ)?


Let’s return to the original meaning of the word planet which comes from the Greek term plánēs astēr, meaning wandering star. In other words, it’s a bright point of light seen in the sky by naked eyes that moves relative to most of the others that appear fixed.

By that definition the only planets are Mercury, Venus, Mars, Jupiter and Saturn, although the Sun and Moon were sometimes considered to be planets. Uranus and Vesta might be included, since sharp eyed observers can detect them, but the ancients apparently never did. Of course the Earth is not a planet, since we do not look up into the night sky to see it. ;)

agingjb
2015-Nov-11, 06:58 PM
Centaur's definition would have to insist on point, otherwise comets might be included (although why not?)

I still think the obsession with what a body orbits is misplaced. But what term includes Titan etc.?

Centaur
2015-Nov-11, 07:33 PM
Centaur's definition would have to insist on point, otherwise comets might be included (although why not?)

I still think the obsession with what a body orbits is misplaced. But what term includes Titan etc.?

That's a good "point", although in earlier times comets as well as meteors were thought to be meteorological phenomena originating in the atmosphere. We could also throw in as candidate planets Jupiter's satellites Ganymede and Callisto, which can be seen by naked eyes with the proper techniques, although ancients may never have done so.

swampyankee
2015-Nov-11, 11:40 PM
I've expressed my dislike of the IAU's planet/dwarf planet definitions, mostly in that I think that sort of categorization should depend on the bodies' intrinsic properties, not an extrinsic one like "clearing its orbit": use some intrinsic characteristic like mass or diameter, not one that would result in a different categorization if the same object is moved to a different semi-major axis.

DaveC426913
2015-Nov-12, 02:21 PM
Let’s return to the original meaning of the word planet which comes from the Greek term plánēs astēr, meaning wandering star. In other words, it’s a bright point of light seen in the sky by naked eyes that moves relative to most of the others that appear fixed.

By that definition the only planets are Mercury, Venus, Mars, Jupiter and Saturn, although the Sun and Moon were sometimes considered to be planets. Uranus and Vesta might be included, since sharp eyed observers can detect them, but the ancients apparently never did. Of course the Earth is not a planet, since we do not look up into the night sky to see it. ;)

This puts the number of planets in the universe at nine or less. And no name to describe the thousand-or-so exo-bodies discovered to-date.

Perhaps a definition that's a little more useful moving forward?

George
2015-Nov-12, 02:30 PM
Here is his paper (pdf) (http://arxiv.org/pdf/1507.06300v4.pdf).

Swift
2015-Nov-12, 03:09 PM
Here is his paper (pdf) (http://arxiv.org/pdf/1507.06300v4.pdf).
Thanks for that link. I just glanced through the paper, but quite interesting. Figures 1 and 2 seem to clearly show that Pluto and the dwarf planets are in a completely different category than the other eight.

Centaur
2015-Nov-12, 03:54 PM
And no name to describe the thousand-or-so exo-bodies discovered to-date.


Stellar satellites

Zartan
2015-Nov-12, 04:07 PM
Definition of a 'planet' is quite arbitrary and made up to classify the objects we currently know of. Before, we knew nine bodies which were clearly distinct from all other solar system objects so the definition made sense. Then we discovered that one of these objects was not actually all that distinct leaving us to redefine 'planet' as it was obvious that remaining eight were very distinct from the rest and thus deserving their own classification.
Now, it's certainly possible that we find some new object, maybe some Mars-sized body orbiting the Sun some 120+ AU's away, making again mockery of our previous definition. But until that happens I see no reason to start tampering with the definition of the 'planet' again based on just some speculative objects which could exist.

George
2015-Nov-12, 05:52 PM
Thanks for that link. I just glanced through the paper, but quite interesting. Figures 1 and 2 seem to clearly show that Pluto and the dwarf planets are in a completely different category than the other eight.

In his last formulation for a single star, it seems a star with 60% the mass of the Sun would adopt Pluto as a planet [note following "Oops], so some tweaking may be in order. [There's something about a 9/8 exponent that catches the eye. :)]

[Oops, I see I accidentally used Mars instead of Earth for the planet ratio. So Pluto would have to be within 5 AU to be a planet, not 39 AU (for a 60% solar mass).]

Amber Robot
2015-Nov-12, 07:12 PM
Definition of a 'planet' is quite arbitrary and made up to classify the objects we currently know of. Before, we knew nine bodies which were clearly distinct from all other solar system objects so the definition made sense. Then we discovered that one of these objects was not actually all that distinct leaving us to redefine 'planet' as it was obvious that remaining eight were very distinct from the rest and thus deserving their own classification.

The history is a little more complex than that, because we've been through this once before. Ceres was originally classified as a planet, but then "demoted" when the rest of the asteroid belt started being discovered. It's also not obvious that Mercury is really that distinct from Pluto. Certainly it's more massive, but according to Margot's paper Mercury wouldn't necessarily pass the planet test if it orbited where Pluto does. Many planetary scientists and astronomers share swampyankee's point of view that the definition should be based on intrinsic not extrinsic properties.

George
2015-Nov-12, 08:37 PM
...according to Margot's paper Mercury wouldn't necessarily pass the planet test if it orbited where Pluto does. Nice point, though for about 1/3 of its orbit it would have a distance that would produce a "planet" result (ignoring that the real distance used is the semi major axis).

Zartan
2015-Nov-12, 10:29 PM
Haven't read Margot's paper, but many redefinition proposals seem to be just carefully engineered excuses to make Pluto planet again...

George
2015-Nov-12, 10:33 PM
Haven't read Margot's paper, but many redefinition proposals seem to be just carefully engineered excuses to make Pluto planet again... Yet not in this case. See Fig. 1 in the paper.

Amber Robot
2015-Nov-12, 11:38 PM
I don't have the time to compare, but I'm curious about how Margot's paper differs from Soter's paper from 2007 on how to quantify "clearing the orbit".

StupendousMan
2015-Nov-13, 02:55 AM
One of the important features of Margot's definition is that it can be done using only those quantities (period of orbit, star mass, and planet mass) which are easily measured for objects orbiting other stars (okay, so planetary mass isn't always easy to determine). That means that if one adopts his definition, one can easily apply the classification to planets around other stars.

Ken G
2015-Nov-13, 01:54 PM
Personally, I think any definition of "planet" that says dwarf planets, and exoplanets, are not planets, is quite silly. We just don't define an overarching class as if it was a subclass, that makes no sense.

George
2015-Nov-13, 05:02 PM
Personally, I think any definition of "planet" that says dwarf planets, and exoplanets, are not planets, is quite silly. We just don't define an overarching class as if it was a subclass, that makes no sense. Isn't the purpose more to establish the subclass not the planets (endoplanets) and exoplanets? I don't think astronomers should let biologists and particle physicists have the greater taxonomy given their smaller realms. ;)

George
2015-Nov-13, 05:16 PM
Back to Amber's mercurial point, a Hill radius of sq. root of 3, rather than 2x that, would take Mercury to about 55 AU. A bit ad hoc but perhaps effective.

Ken G
2015-Nov-13, 11:38 PM
Isn't the purpose more to establish the subclass not the planets (endoplanets) and exoplanets?
I just mean that if you take the definition of a "planet" given in the OP, then no exoplanet is a planet. Does that make sense?

slang
2015-Nov-13, 11:58 PM
"According to Margot, the current system has created a “definitional limbo” for newly discovered bodies outside the solar system, as one of the prerequisites for a planet is that it orbits the sun."

But that was known at the time of adopting the current definition, and left as "exercise for later", wasn't it?

Ken G
2015-Nov-14, 12:31 AM
Perhaps, but I didn't think it was a good idea to leave that exercise open. We should use inclusive definitions of main categories, and leave the specifics to subgroups. So I think they were asking the wrong question-- they were asking "how should we define a planet such that the definition separates the 8 major ones in our solar system from everything else," but they should have asked "what do we call the 8 major planets in our own solar system so we'll know when we are talking about them." I think "major planet" would have done fine, or perhaps "major solar planet" if we want to restrict to just those 8.

George
2015-Nov-15, 09:10 PM
Perhaps, but I didn't think it was a good idea to leave that exercise open. We should use inclusive definitions of main categories, and leave the specifics to subgroups. So I think they were asking the wrong question-- they were asking "how should we define a planet such that the definition separates the 8 major ones in our solar system from everything else," but they should have asked "what do we call the 8 major planets in our own solar system so we'll know when we are talking about them." I think "major planet" would have done fine, or perhaps "major solar planet" if we want to restrict to just those 8. I think our 8 were more their test of any proposal than otherwise.

"Major planet" would have been a good idea if proposed back in the 1860s during the first(?) round of planetary demotions (eg. Ceres). These demotions came for the same reason but addressed differently, I suspect. As I understand it, (see next post) they found too many neighbors for Ceres. No estate or hacienda can hold their title once they are discovered to be an apartment complex, regardless of the size of the penthouse. Orbital clearing is another way of proving estatehood, as long as such is inevitable in time. The ability to establish such and "estatehood" (ie planet) from observations (as StupendusMan noted) makes for a solid distinction functionally applicable to exoplanets.

"Planet" is too indelible a term to change, IMO. The Pluto demotion affair may be an indicator of that, dog gone it! The 8 are truly "wandering stars" and each bright enough to be seen on dark nights, so they are a reasonable test, though arbitrary since much dimmer ones will, and should be, allowed by proposals such as this one. [Another argument not to let the Earth be the center of the universe; 8 is not enough planets for the universe.]

I can't imagine changing our use of "planet" with its thousands of years of use. I must admit that I fell prey to my own bias when I did not want (above) to see the planet Mercury demoted if moved to Pluto's distance. But it should be since it would not clear a path even if it would be better inclined to do so (sorry).

George
2015-Nov-15, 09:50 PM
Since I am using asteroids as an analogy, it should be noted that Olber's discovery of Pallas caused him to posit his theory that a trans-Martian planet had become fragmented. This brought hiss prediction that others would be found at the nodes. When they were, his theory became stronger. So the story is more than just numbers in an orbit. Pretty cool story given it was 4 decades before Neptne's discovery.

Ken G
2015-Nov-16, 04:26 PM
The ability to establish such and "estatehood" (ie planet) from observations (as StupendusMan noted) makes for a solid distinction functionally applicable to exoplanets.I have no issue with the categories that are being defined, my issue is in calling one of them the definition of "planet." An exclusive subcategory should not be given the title of an inclusive supercategory, that's just bad nomenclature, though not bad categorization.


"Planet" is too indelible a term to change, IMO.I agree that everyday words tend to adopt every day meanings, that science cannot affect too much. But I'm strictly talking about the scientific meaning-- when we find the term "planet" used in astronomical papers, for example. The definition in the OP does not make sense as the one that should be used in that context, because if one does, then minor planets, dwarf planets, and exoplanets, are not planets.

Since I am using asteroids as an analogy, it should be noted that Olber's discovery of Pallas caused him to posit his theory that a trans-Martian planet had become fragmented.Yes, the history of scientific discovery is a good context for talking about why we should have various categories. The categories can be debated, but I'm only talking about the names of the categories.

George
2015-Nov-16, 10:28 PM
I have no issue with the categories that are being defined, my issue is in calling one of them the definition of "planet." An exclusive subcategory should not be given the title of an inclusive supercategory, that's just bad nomenclature, though not bad categorization....
I agree that everyday words tend to adopt every day meanings, that science cannot affect too much. But I'm strictly talking about the scientific meaning-- when we find the term "planet" used in astronomical papers, for example. The definition in the OP does not make sense as the one that should be used in that context, because if one does, then minor planets, dwarf planets, and exoplanets, are not planets. All great points and what you're saying is indicative across the board. The word 'car" does not refer to any particular car. "Ice cream" rarely means vanilla. [I'm pretty sure this is what you are saying, though I often need multiple analogies this time of the day.]

But there are exceptions. Coke can mean Dr. Pepper. Or, more to our question, there is Coke and then their is Coke Zero, diet Coke, cherry Coke, vanilla Coke, etc. These are sub-cokes; variations from the original. The indelible idea for the word planet has been around much longer and still should refer to those original wandering stars, else it will loose its flavor (mixing things up as usual).

Hornblower
2015-Nov-16, 11:19 PM
In my opinion, using the gravitational neighborhood clearing capability, or lack thereof, as a discriminator in a classification scheme makes the scheme scientifically useful, at least in our own planetary system. I don't think the usefulness would be hurt one iota if we say major planet and dwarf planet, rather than calling the majors "planet" without an adjective and saying that dwarf planets "are not planets." After all, if something the size and albedo of Pluto had been as close in as Mars, the ancient Greeks would have seen it and called it a planet in the original sense of the word.

Ken G
2015-Nov-17, 06:22 AM
And you can be sure that "planetologists" are just as interested in dwarf planets as major planets, they all tell part of the story. It's true that "Coke" predates "diet Coke", but scientific terms should be held to a more useful standard.

George
2015-Nov-17, 04:40 PM
And you can be sure that "planetologists" are just as interested in dwarf planets as major planets, they all tell part of the story. It's true that "Coke" predates "diet Coke", but scientific terms should be held to a more useful standard. Perhaps if they do become "major planets", to improve things for the reasons you state, there would be little common use change. "Coke" is short for "Coca-Cola" and "planet" would just be short for "major planet".

agingjb
2015-Nov-17, 05:08 PM
I hope that "planetologists" study some things that are not planets under any proposed definitions - although maybe the obsession with what things orbit has an effect on their funding.

"Telescope time for Triton? That's not a planet. Go away."

George
2015-Nov-17, 05:24 PM
I hope that "planetologists" study some things that are not planets under any proposed definitions - although maybe the obsession with what things orbit has an effect on their funding.

"Telescope time for Triton? That's not a planet. Go away." Do we not have Tritonologists yet?"

Amber Robot
2015-Nov-17, 06:42 PM
In my opinion, using the gravitational neighborhood clearing capability, or lack thereof, as a discriminator in a classification scheme makes the scheme scientifically useful, at least in our own planetary system.

What scientifically useful concepts is that discriminating between?

Hornblower
2015-Nov-18, 02:24 AM
What scientifically useful concepts is that discriminating between?

It distinguishes between a massive body that is nearly all of the total mass in the vicinity of its orbit and a not so massive body that could have as much or more other mass sharing its neighborhood. This gives the planetary astronomers the big picture of the structure and perhaps the evolution of the solar system.

Ken G
2015-Nov-18, 03:12 AM
Perhaps if they do become "major planets", to improve things for the reasons you state, there would be little common use change. Yes, I'm sure that no matter what official definition of "planet" is adopted, planetologists are going to call the Moon a planet, and Pluto a planet, and Europa a planet, and so on. They are going to say their satellite "orbited the planet" or their rover "touched down on the planet", because that's just what they mean by a planet, a large object that isn't a star that is undergoing investigation. It's all about making comparisons, so if Titan has an atmosphere similar to Earth, and a rocky surface with some similarities and differences, they are going to compare Titan to the Earth, and in that comparison it is not important that Titan is a moon and the Earth is a major planet, it only matters that we are asking similar questions about both, uniting them both into a single object class, and "planet" is basically the only word readily available for doing that.

kzb
2015-Nov-18, 12:44 PM
The original meaning of the word planet was "wanderer". Now we know that would include basically everything in the universe, maybe the whole thing wants revising root and branch. The word wanderer is no longer appropriate.

The difference between a hill and a mountain is height. In the UK a mountain is over 2000 feet high, smaller increases in topography are hills or (even smaller) hillocks. In other words there is an arbitrarily chosen size which defines the classification.

Get rid of the word planet to avoid confusion. Invent new words for objects in a stellar system according to arbitrary size definitions. Satellites could be distinguished by a secondary adjective.

How about that?

George
2015-Nov-18, 02:40 PM
Yes, I'm sure that no matter what official definition of "planet" is adopted, planetologists are going to call the Moon a planet, and Pluto a planet, and Europa a planet, and so on. I assume they don't speak this way to a general audience in order to eschew obfuscation. But I have not, regrettably, heard their presentations, so maybe they are more consistent with this view of the use of "planet". At home, I might ask for a coke meaning a Dr. Pepper, but only informally.

Amber Robot
2015-Nov-18, 06:12 PM
It distinguishes between a massive body that is nearly all of the total mass in the vicinity of its orbit and a not so massive body that could have as much or more other mass sharing its neighborhood. This gives the planetary astronomers the big picture of the structure and perhaps the evolution of the solar system.

In general, I agree with this. I believe that a distinction can be made between "stand-alone" objects and objects that are simply the largest in a distribution of objects sharing similar orbital and other characteristics. Unfortunately, I'm not quite sure we are at the state of both data and theory knowledge to really understand how Pluto, for example, fits in with its distribution because we don't have much more information than orbital about the other members in the distribution. Things are probably more clear in the case of Ceres. Mercury may be a stand-alone simply because the parameter space is small so close to the Sun.

Hornblower
2015-Nov-18, 09:45 PM
The original meaning of the word planet was "wanderer". Now we know that would include basically everything in the universe, maybe the whole thing wants revising root and branch. The word wanderer is no longer appropriate.
I disagree. The five starlike objects that the ancient Greeks saw wandering are now known to be in the same broad category physically, that is, nearby nonluminous bodies gravitationally bound to the Sun and visible by reflected sunlight. The "fixed" stars are in another broad category, that is, vastly more remote and self-luminous bodies whose motion is too slight to be visible to the unaided eye in a human lifetime. I see no scientific downside to co-opting the term "planet" for the likes of Uranus and Neptune, which the ancient Greeks could not see, along with the five bright ones, along with the Earth and with similar bodies that are gravitationally bound to other stars. While we are at it, let's include rogues that have been ejected from stellar systems by close encounters with perturbing bodies.

Get rid of the word planet to avoid confusion. Invent new words for objects in a stellar system according to arbitrary size definitions. Satellites could be distinguished by a secondary adjective.

How about that? Competent astronomers are not confused. If some members of the general public are confused because of their own failure to pay attention to detail and get themselves well informed, tough cookies.

agingjb
2015-Nov-18, 10:49 PM
Competent astronomers are not confused. If some members of the general public are confused because of their own failure to pay attention to detail and get themselves well informed, tough cookies.

Says it all really. I shall try not to slam the door on my way out. Yes, flounce.

Hornblower
2015-Nov-19, 03:17 AM
I disagree. The five starlike objects that the ancient Greeks saw wandering are now known to be in the same broad category physically, that is, nearby nonluminous bodies gravitationally bound to the Sun and visible by reflected sunlight. The "fixed" stars are in another broad category, that is, vastly more remote and self-luminous bodies whose motion is too slight to be visible to the unaided eye in a human lifetime. I see no scientific downside to co-opting the term "planet" for the likes of Uranus and Neptune, which the ancient Greeks could not see, along with the five bright ones, along with the Earth and with similar bodies that are gravitationally bound to other stars. While we are at it, let's include rogues that have been ejected from stellar systems by close encounters with perturbing bodies.
Competent astronomers are not confused. If some members of the general public are confused because of their own failure to pay attention to detail and get themselves well informed, tough cookies.

Addendum: If some members of the general public are confused as a result of bad writing by popular media dilletantes, they are welcome to come here and get lots of help.

Ken G
2015-Nov-19, 05:09 AM
I assume they don't speak this way to a general audience in order to eschew obfuscation. They might slip into it, if they are very used to it. The public catches on pretty quickly I think (like, "oh, I guess the professionals don't bother with the somewhat useless distinctions that seem so important in popular science reporting....").
At home, I might ask for a coke meaning a Dr. Pepper, but only informally.It's human nature. You use words in the way that serves you, not in the way that conforms to what it says in dictionaries. The dictionaries eventually respond to how the words serve us. After all, which had to come first?

kzb
2015-Nov-19, 05:38 PM
I was being ironic you know. I don't seriously think the word planet could be dropped.

But terminology is often changed, and can be quite successful when things have become ambiguous. We now should use "radionuclide" rather than "isotope" for a radioactive nucleus for example.

George
2015-Nov-19, 09:55 PM
I was being ironic you know. I don't seriously think the word planet could be dropped.

But terminology is often changed, and can be quite successful when things have become ambiguous. We now should use "radionuclide" rather than "isotope" for a radioactive nucleus for example.
That reminds me that elements are sometimes named after planetary discovery including Ce, U, Np, Pd (for Pallas), and Pu. Luckily, plutonium is more of a dwarf element (furthering irony). Is Ge named after our 7th planet?

Where are we going to get new elements?? ;)

Fiery Phoenix
2015-Nov-19, 11:04 PM
I always felt definitions were all over the place in astronomy. And while I'm one of those who support the IAU's 2006 definition, it's evidently insufficient when it comes to exoplanets. This may not be an issue right now, but in a few years when our telescopes start detecting smaller exoplanets (<= 1 MEarth), it will be more apparent, because at one point someone somewhere is going to ask if we have discovered 'exo-dwarf planets' (that's quite a mouthful).

swampyankee
2015-Nov-20, 01:02 AM
Where are we going to get new elements?? ;)

Darmstadt, Berkely, and Dubna.

George
2015-Nov-20, 01:57 PM
I always felt definitions were all over the place in astronomy. And while I'm one of those who support the IAU's 2006 definition, it's evidently insufficient when it comes to exoplanets. This may not be an issue right now, but in a few years when our telescopes start detecting smaller exoplanets (<= 1 MEarth), it will be more apparent, because at one point someone somewhere is going to ask if we have discovered 'exo-dwarf planets' (that's quite a mouthful). The paper's proposal shows that we can now quantify the term. It is 2 dimensional: mass (star and object) and orbital distance. These values can be determined for our Solar System as well as for others.

Ken G
2015-Nov-20, 03:21 PM
This may not be an issue right now, but in a few years when our telescopes start detecting smaller exoplanets (<= 1 MEarth), it will be more apparent, because at one point someone somewhere is going to ask if we have discovered 'exo-dwarf planets' (that's quite a mouthful).Margot's proposal allows us to make these categorizations from Earth, but it still suffers from the core problem-- is an exo-dwarf-planet an exoplanet, or not? Because it's not a "planet" in that scheme. In my book, if its name ends in "planet", it's a planet, or the nomenclature is NFG (not ferry good).

George
2015-Nov-20, 05:26 PM
Margot's proposal allows us to make these categorizations from Earth, but it still suffers from the core problem-- is an exo-dwarf-planet an exoplanet, or not? Because it's not a "planet" in that scheme. In my book, if its name ends in "planet", it's a planet, or the nomenclature is NFG (not ferry good). Perhaps the use of "planetoids" (planet-like) would be more sensible. A heirarchy such as planets/planetoids/asteroids & comets/planetismals/dust/gas. Planetoids would be dwarf planets per the IAU definition. Maybe a label for the KBOs and Oort cloud chunks larger than planetismals but smaller than planetoids would be appropriate.

Fiery Phoenix
2015-Nov-20, 06:12 PM
Margot's proposal allows us to make these categorizations from Earth, but it still suffers from the core problem-- is an exo-dwarf-planet an exoplanet, or not? Because it's not a "planet" in that scheme. In my book, if its name ends in "planet", it's a planet, or the nomenclature is NFG (not ferry good).
We'd probably want to be more lenient when classifying exoplanets. As George noted, something like a 'planetoid' would be appropriate. In reality, I don't think we'll ever actually use the term exo-dwarf-planet in a professional sense. It's too specific.

Ken G
2015-Nov-20, 08:59 PM
Perhaps the use of "planetoids" (planet-like) would be more sensible.It would certainly avoid the "dwarf planet is not a planet" problem! Personally, I prefer inclusive general terms, so was never enamored of the exclusive "planet" definition, though I certainly do think some categorization that separates Pluto from Earth is valid.

Ken G
2015-Nov-20, 09:00 PM
We'd probably want to be more lenient when classifying exoplanets. As George noted, something like a 'planetoid' would be appropriate. In reality, I don't think we'll ever actually use the term exo-dwarf-planet in a professional sense. It's too specific.
Yes, I think planetologists are going to call all these things planets, even moons.

DaveC426913
2015-Nov-20, 10:49 PM
Yes, I think planetologists are going to call all these things planets, even moons.

Well, at least we know what sperm whales will call it.


And wow! Hey! What’s this thing suddenly coming towards me very fast? Very very fast. So big and flat and round, it needs a big wide sounding name like … ow … ound … round … ground! That’s it! That’s a good name – ground!

I wonder if it will be friends with me?

And the rest, after a sudden wet thud, was silence.

Hornblower
2015-Nov-21, 12:06 AM
We could argue until doomsday about what word or phrase to use as a name for a particular category of orbiting bodies without solving a fundamental problem, which as I see it is poor communication. Astronomers should be able to tell their colleagues and the general public how and why they are classifying these objects the way they do, and should be able to avoid being spooked by overwrought, unreasoning emotional outbursts from the public about issues like how to classify Pluto. I think many of the delegates at the 2006 IAU General Assembly performed poorly in this respect.

Fiery Phoenix
2015-Nov-21, 12:27 AM
We could argue until doomsday about what word or phrase to use as a name for a particular category of orbiting bodies without solving a fundamental problem, which as I see it is poor communication. Astronomers should be able to tell their colleagues and the general public how and why they are classifying these objects the way they do, and should be able to avoid being spooked by overwrought, unreasoning emotional outbursts from the public about issues like how to classify Pluto. I think many of the delegates at the 2006 IAU General Assembly performed poorly in this respect.
If what I heard is accurate, only a small percentage of the total IAU population had a say in the 2006 classification. If I remember correctly, the majority weren't at the meeting at the time, and the voting only included those who happened to be in the right place at the right time.

Hornblower
2015-Nov-21, 02:03 AM
If what I heard is accurate, only a small percentage of the total IAU population had a say in the 2006 classification. If I remember correctly, the majority weren't at the meeting at the time, and the voting only included those who happened to be in the right place at the right time.If I remember correctly, there were about 400 delegates remaining for that action, out of some 3,000 present earlier in the assembly and some 10,000 members total. They were tying themselves in knots over what should have been a routine reclassification action driven by recent discoveries. I imagine the others were either sightseeing in Prague or on their way home. It is ridiculous for such a small portion of the membership to be a quorum.

Solfe
2015-Nov-21, 02:55 AM
If I remember correctly, there were about 400 delegates remaining for that action, out of some 3,000 present earlier in the assembly and some 10,000 members total. They were tying themselves in knots over what should have been a routine reclassification action driven by recent discoveries. I imagine the others were either sightseeing in Prague or on their way home. It is ridiculous for such a small portion of the membership to be a quorum.

If only we had a electronic system of machines that could be used to discuss things and vote, so that all the members didn't have to travel the world to consider new ideas.

Fiery Phoenix
2015-Nov-21, 05:55 AM
If only we had a electronic system of machines that could be used to discuss things and vote, so that all the members didn't have to travel the world to consider new ideas.
I see what you did there :p