The first 8 planets fit in a relatively consistent model; when Pluto was discovered, it was far enough away that we didn't realize how different it was from the other planets. We didn't even get a handle on how small it was until (IIRC) the 1970s, which is when we realized that what we thought was "Pluto" was really "Pluto and Charon."
Pluto is really just the closest of a whole cluster of similar bodies which may be orbiting the sun as far as a light year out.
I worked for $BIG_PHARMA_CO for a while, and they considered the issue a tremendous problem. They are used to saving research data for a century and are deeply worried that 50 years from now they won't be able to read their current data, because of format changes and media degradation.
The existing "classic" 9 planets retain their status, even if they defy whatever definition they come up with, I don't really care what definition they use. They can always make explicit exceptions for historical reasons.
This is certainly the most common attitude, but I don't understand it - why do you care whether or not Pluto is a planet or a just one of the biggest Kuiper Belt Objects?
Think for a moment - substitute "7 track tape" for "cd rom", now tell me how you would find out what file format was used.
The redbook definition is certainly more widely disseminated than the encoding methods for 1960's tape storage but you're still underestimating the skills a person needs to read the CD is also capable of finding, reading, understanding and coding to the redbook standard.
* Pluto's orbit is retrograde, eccentric and tipped. * Our moon, and several others, are larger than Pluto. In fact, our moon is three times larger than Pluto. * Mercury has less "atmosphere" than many comets
As a word "planet" has no technical value, it's original meaning was "a star that moves" and that's probably as good a definition as any. There's no point in trying to force it into some rules-based definition when we could just as easily use modifiers to explain what we're talking about - "rocky planet", "icy planet", "gas planet", "minor planet", etc..
Pluto's orbit is eccentric enough that it passes closer to the sun than Neptune (but never gets close to Neptune - think "spirograph") It's also significantly tilted with respect to the rest of the solar system.
All the asteroids, comets and Kupier belt object exist in the context of the Solar System and were formed through the same mechanisms as the major planets.
Pride and bragging rights. The guy who discovered Neptune and Pluto became celebrities, and everyone still knows what they found even if few still remember their names. The guys who hunt comets (for example) can find dozens over a career and few will know their names, or the things they found.. Discovering a "planet" is a much bigger deal than discovering "yet another rock"
Khyber: "Comets, I think would not fit this definition, nor asteroids, simply because their orbit does not follow the regular path of orbit that the other planets do"
Porkchop: "I dispute your claim that asteroids have irregular orbits, Ceres and Vesta have orbits every bit as predictable as the Earth's and so do most other asteroids."
Khyber: "Did you not read the part which I specifically said excluded the asteroids orbiting between Mars and Jupiter??"
Now, which of us can't read?
BTW, "common sense" has no place at all in the scientific method. No does our "CURRENT DEFINITION" of a planet since, in fact, we don't have one.
The center of gravity of the combined earth-moon system is beneath the crust of the earth.
Think about it - the moon is only a few percent of the earth's mass - as we orbit around the sun together, the moon does all the swinging around, the earth just wobbles a bit.
by that definition, every single one of the tens of thousands of Kupier belt objects (of which Pluto is one) are now planets.
And I dispute your claim that asteroids have irregular orbits, Ceres and Vesta have orbits every bit as predictable as the Earth's and so do most other asteroids.
Saturn and Uranus were titans - beings that came before the gods. Neptune was named in modern times, but they kept the roman naming tradition, same with Pluto, Roman god of the dead.
And then they proceeded to waste all the other greek and roman names on every rock, brick and crater they could find which is why we're reduced to naming moons after Shakespearean characters.
The naming of Charon was a slick trick - the discoverer specified that the name be spelled like the name of the mythical figure, but that the name be pronounced "Sharon" - which happened to be the guys wife.
But it's an arbitrary distinction since waterways keep right on changing even after they get an official name.
In my area, we've got a Perkiomen Creek that is quite wide (and serious enough to have cut a nice valley) but the Manatawny River barely qualifies as "wet" if you ask me.
Oh, and we tend to call them "criks" in Pennsylvania, too.
First, you have no definition of big, but assuming you mean "large enough for gravity to pull it into a sphere" then astronomers currently estimate 40-50 such bodies exist in the Kupier belt.
So, are *you* planning to memorize the names of an extra 40-50 planets over the next several decades?
Slashdot Mirror
The first 8 planets fit in a relatively consistent model; when Pluto was discovered, it was far enough away that we didn't realize how different it was from the other planets. We didn't even get a handle on how small it was until (IIRC) the 1970s, which is when we realized that what we thought was "Pluto" was really "Pluto and Charon."
Pluto is really just the closest of a whole cluster of similar bodies which may be orbiting the sun as far as a light year out.
in 10 years we haven't solved the problem.
I worked for $BIG_PHARMA_CO for a while, and they considered the issue a tremendous problem. They are used to saving research data for a century and are deeply worried that 50 years from now they won't be able to read their current data, because of format changes and media degradation.
The existing "classic" 9 planets retain their status, even if they defy whatever definition they come up with, I don't really care what definition they use. They can always make explicit exceptions for historical reasons.
This is certainly the most common attitude, but I don't understand it - why do you care whether or not Pluto is a planet or a just one of the biggest Kuiper Belt Objects?
Think for a moment - substitute "7 track tape" for "cd rom", now tell me how you would find out what file format was used.
The redbook definition is certainly more widely disseminated than the encoding methods for 1960's tape storage but you're still underestimating the skills a person needs to read the CD is also capable of finding, reading, understanding and coding to the redbook standard.
increasing the number of planets to 40 or 50? Because that's the estimated number of Pluto-sized objects waiting to be discovered.
Sedna, Quaoar, 2003UB13, 2003EL61, and 2004DW are all planets?
* Pluto's orbit is retrograde, eccentric and tipped.
* Our moon, and several others, are larger than Pluto. In fact, our moon is three times larger than Pluto.
* Mercury has less "atmosphere" than many comets
As a word "planet" has no technical value, it's original meaning was "a star that moves" and that's probably as good a definition as any. There's no point in trying to force it into some rules-based definition when we could just as easily use modifiers to explain what we're talking about - "rocky planet", "icy planet", "gas planet", "minor planet", etc..
so does the Moon.
Pluto's orbit is eccentric enough that it passes closer to the sun than Neptune (but never gets close to Neptune - think "spirograph") It's also significantly tilted with respect to the rest of the solar system.
All the asteroids, comets and Kupier belt object exist in the context of the Solar System and were formed through the same mechanisms as the major planets.
Pride and bragging rights. The guy who discovered Neptune and Pluto became celebrities, and everyone still knows what they found even if few still remember their names. The guys who hunt comets (for example) can find dozens over a career and few will know their names, or the things they found.. Discovering a "planet" is a much bigger deal than discovering "yet another rock"
Thee most obvious reason something would be a dominant body would be if it had moons. Neither of those do.
You fail it.
Where do you think the Kupier belt came from?
Pluto, comets, asteroids, little frozen knickknacks a quarter of a light year away, all formed from the "accretion disk".
is probably larger than pluto.
except for the huge PR backlash when they tried to "demote" Pluto.
I think we should abandon "planet" as a technical term and simply adopt terms that reflect reality better - "rocky planet", "minor planet", etc..
The term "planet" has no real technical meaning, we should develop descriptive terms for types of celestial bodies (rocky, icy, gassy, dopey, etc..)
Khyber: "Comets, I think would not fit this definition, nor asteroids, simply because their orbit does not follow the regular path of orbit that the other planets do"
Porkchop: "I dispute your claim that asteroids have irregular orbits, Ceres and Vesta have orbits every bit as predictable as the Earth's and so do most other asteroids."
Khyber: "Did you not read the part which I specifically said excluded the asteroids orbiting between Mars and Jupiter??"
Now, which of us can't read?
BTW, "common sense" has no place at all in the scientific method. No does our "CURRENT DEFINITION" of a planet since, in fact, we don't have one.
The center of gravity of the combined earth-moon system is beneath the crust of the earth.
Think about it - the moon is only a few percent of the earth's mass - as we orbit around the sun together, the moon does all the swinging around, the earth just wobbles a bit.
Why not just admit the word has no useful technical definition and leave it at that?
by that definition, every single one of the tens of thousands of Kupier belt objects (of which Pluto is one) are now planets.
And I dispute your claim that asteroids have irregular orbits, Ceres and Vesta have orbits every bit as predictable as the Earth's and so do most other asteroids.
What the heck do they teach kids these days?
Saturn and Uranus were titans - beings that came before the gods. Neptune was named in modern times, but they kept the roman naming tradition, same with Pluto, Roman god of the dead.
And then they proceeded to waste all the other greek and roman names on every rock, brick and crater they could find which is why we're reduced to naming moons after Shakespearean characters.
The naming of Charon was a slick trick - the discoverer specified that the name be spelled like the name of the mythical figure, but that the name be pronounced "Sharon" - which happened to be the guys wife.
a comet or a leaky space probe is a planet.
But it's an arbitrary distinction since waterways keep right on changing even after they get an official name.
In my area, we've got a Perkiomen Creek that is quite wide (and serious enough to have cut a nice valley) but the Manatawny River barely qualifies as "wet" if you ask me.
Oh, and we tend to call them "criks" in Pennsylvania, too.
"planet" is a social term, not a technical one and freeze the list of planets at 9.
This leaves us free to give the things we discover designations that reflect their structure or their position.
I *do* think we will eternally regret wasting so many perfectly good names on moonlets and asteroids.
First, you have no definition of big, but assuming you mean "large enough for gravity to pull it into a sphere" then astronomers currently estimate 40-50 such bodies exist in the Kupier belt.
So, are *you* planning to memorize the names of an extra 40-50 planets over the next several decades?
It could be a creek or a stream.