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How Would You Define a Planet?
It doesn't come easy asks: "The argument over the definition of a planet continues. So far, two definitions are favored but without much consensus so far: base the definition of a planet simply on an object's size. Pluto would be near the lower limit and the newly discovered Kuiper Belt objects could also qualify, giving us 10 or 11 planets so far; or define the single dominant body in its immediate neighborhood as the only qualifying object for planetary status. If no one body dominated (such as the millions of individual asteroids in the asteroid belt) then none would qualify for planetary status. In this case Pluto would be disqualified (Neptune would be the dominant body in Pluto's region of space), and the newly discovered Kuiper Belt objects would also fail to qualify. The International Astronomical Union (IAU) working group charged with pinning down the definition of a planet may vote on the proposals within the next two weeks (or they may decide to start all over again with something new). Maybe Slashdot readers can give them some help. How would you define a planet?"
sounds good enough for me ;-)
What could possibly hurt the security of the American people more than giving our own government the ability to hide its
The obvious conditions are round shape and orbits the sun. Size is somewhat subjective although to have a round shape it would have to be above a certain mass.
Oataox or whatever the hell? The guy who came up with that needs to be kicked out of the Astronomy club.
"Ain't no right way to do a wrong thing."
Personally, I think a good definition of a major planet is one that is massive enough that, given its composition, it assumes a sphere-like shape.
cb
Oooh! What does this button do!?
The public will be happy to learn of more planets -- it feels like progress. It'll be hard to convince the public we lost a planet somehow. That sounds like an unimportant consideration, but I don't want us giving the Creationists more ammo for their arguments that Science is fickle. "They used to think there were nine planets, but then they found they were WRONG!"
It's not like any serious science rests on this definition anyway.
--Greg
A nonluminous celestial body larger than an asstroid or cumbucket, illuminated by light from a star, such as Michael Jackson, around which it revolts.
Uncyclopedia: Planet
If it's the size of Marvin's brain, or bigger, it's a Planet.
... well, it's just depressing.
If it's smaller
Wretched, isn't it?
Words like "planet" are meant to "carve nature at its joints". Problems arise when historically there appeared to be joints (planets moved differently than stars in the sky) but, we are learning now that there are no useful joints here. Why bother defining the word planet at all? Is it really that useful to astronomers? And why, say, want Mercury (a small rocky body with no atmospere) to be grouped in a category with Jupiter (a large, mostly gaseous body with an atmosphere) instead of with asteroids (small, rocky bodies with no atmospere)?
I suggested this on www.randi.org a few weeks ago. In Pluto's case have astrologers draw up two parallel charts. One with Pluto as a planet, the other without. After a few weeks we can compare what happened in the world to the astrology charts and that'll settle it.
"The planets don't lie" as I said there. ;)
Trolling is a art,
I would define it thus: An object is a planet if it has enough gravity to form into a sphere but not large enough to ever had fusion start in its interior and has cleared its orbit of debris left over from its formation. This would allow Pluto to remain a planet, as well as "promote" Sedna to planet stus but rule out Ceres.
CDE open sourced! https://sourceforge.net/projects/cdesktopenv/
No, Xena (one of the new trans-neptunian objects) is quite a bit larger than Pluto, so that would be 10 now.
--The universe will not be altered by forum threads, even those which are very wry. --Tycho Brahe (Penny Arcade)
http://en.wikipedia.org/wiki/Definition_of_Planet
The problem with disqualifying Pluto because of Neptune being the more dominant body falls apart when you consider the eccentric orbit of Pluto and just how far that takes it from Neptune's "region of space".
What exactly is the definition of a region of space?
How much larger must an object be than its neighbors in order to be considered the dominant object of its neighbors? Twice as large? Four times?
wouldn't stars be "planets" as well?
If you can land on it and score with an alien chick, it's a planet.
Orbits a star or stars.
Enough mass so that its gravity forces it into a spherical or an ellipsoid shape.
This defintion does make large astroids like Ceres a planet. Personally, I don't necessarily have a problem with this, but I don't really care. If you want to remove these you can add:
Must be a "free standing" object (i.e. not in a belt)
If you're dead set against Pluto, you can add:
Orbital inclination must be close to the orbital plane.
I not be an astronomer or an astrophysicist, but I really don't see what's so hard about defining a planet. Whatever the Powers That Be(tm) decide, it should be based on physics and not legislation. (e.g. "mass in excess of x metric tons")
...the mice?
If you could reason with religious people, there would be no religious people
I think we should just drop the name. It can still exist, but not in a scientific context. We just go with MVEMJSUNP as "planets" and make up words with given definitions before we start trying to apply them them to things.
BOOS: Big Objects Orbiting Star.
BOOBOOS: Big Objects Orbiting Big Objects Orbiting Star.
LOOS: Little Objects Orbiting Star.
FOSC: Floating Outer Space Crap.
Planet: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, Pluto.
Oh, and since I know you'll ask the difference between a BOOS and a LOOS is that a BOOS is large enough that it's own gravity keeps it roughly spherical.
It is no longer uncommon to be uncommon.
Ignoring for the moment the fact that the gas giants aren't rocky or have molten cores, even Mars wouldn't qualify. Its core cooled and solidified several million years ago, killing its geodynamo (which BTW, may be the reason it lost its water and most of its atmoshpere).
therefore, mercury would NOT be a planet (more like a moon of the sun)
and titan, even though it orbits saturn, WOULD be a planet
i think that makes most the most sense: what an object orbits shouldn't matter, it's composition should be the largest consideration
some other nomenclature can address what it orbits ("a moon of the sun" or "a planet of saturn")
it should be considered either
REGARDLESS of what it orbits
intellectual property law is philosophically incoherent. it is your moral duty to ignore it or sabotage it
Prediction for end of Universe #42: Fencepost error in Quantum_bogosort.cpp
When borderline cases arise, concepts proliferate.
Apart from the Platonists in the audience, intelligent people realize that concepts are made things, artefacts created by humans to facilitate certain types of interaction with the world. Now, the world is a particular way, and that puts constraints on the sorts of concepts that are useful to us, but it doesn't determine a single set of concepts that will do the job. Therefore, concepts vary from person to person, and one person's pornography is another person's erotica, and so on.
Concepts, like all tools, are judged to be better or worse according to use. Some of the uses of "planet" are political--every astronomer monkey wants to be the discoverer of a "plant", because that will attract and impress other monkeys of the complementary sexual orientation. This is just part of our hertiage as monkey's, and we may as well admit it. Other uses are scientific--planetologists already divide planets into sub-categories like "gas giant" and "terrestrial planet", because quite different physical processes dominate these bodies, and distinguishing them allows us to focus our attention more fully on one set of processes or the other. For beings of definitely limited brain power, this is extremely useful.
Historically the term "planet" mixed several completely unrelated things: size, distance from Earth, and being in orbit around the Sun. Planets were "wandering stars", and it just happens that the only things that fell into that category were large bodies far from Earth that orbited the Sun. Things like the Moon, which is close, wasn't a planet because it had a visible disk, which stars do not. But this is entirely accidental--if one of the inner planets had had a moon visible from Earth with the naked eye it is likely that the concept of planet would already be more various than it already is.
I think it better to create a bunch of new terms that acknowledge the rich division of bodies we can now see, rather than get hung up on the historical term "planet". The things we care about include at least three axes: size, composition and orbit. Trying to assign a single word to a particular region of a three-dimensional space (which probably isn't even simply connected!) is a silly waste of time, driven purely by monkey psychology, and has no scientific value. In fact, it may even have negative consequences for science, because getting hung up on historical terms may also help keep people hung up on historical concepts.
So my vote would be to expunge the term "planet" from the astronomical lexicon entirely. It's the only way to be sure.
Blasphemy is a human right. Blasphemophobia kills.
I think you missed a really important one:
/ducks
Big Objects Orbiting Binary Stars...
the above is my personal opinion and does not necessarily reflect that of the little voices in my head
The only way to define it is obvious:
Anything you can blow up with the Death Star!
"City hall" in German is "Rathaus" Kinda explains a few things......
I would add the condition that it must orbit a star, (to exclude moons) and not be a star itself (to exclude binary or multiple stars). And not be part of a belt of similar objects (to exclude Ceres, Juno, Pluto/Charon, and Sedna which are all spherical).
The days of the digital watch are numbered.
If it can support the orbit of the Deathstar then it qualifies.
"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.
Clear, Dark Skies
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.
Clear, Dark Skies
Just for completeness: Saturn comes from Greek Cronos, Uranus from Greek Ouranos, Pluto from Greek Hades.
We also need BFR..."Big Fucking Rock".
I want a new quote. One that won't spill. One that don't cost too much. Or come in a pill.
The bottom line here is that most professional astronomers don't care about these objective definitions. When astronomers are doing research, none of it hangs precariously on the definition of planet or asteroid or something else. They specify what they mean -- Jupiter, or the major gas giants, or the Earth-crossing asteroids, or transneptunian objects, or plutinos.
These names (planet, asteroid, comet, etc.) are just arbitrary labels invented by people, after all. They have no special significance, and they never have. After all, planet comes from the Greek word for "wanderer," a reference to the fact that planets appeared to be stars in the sky that moved. Asteroid means "star-like," a reference to the fact (as astronomical observations improved) they appeared to be moving objects that didn't have observable disks like the other planets (because they are too small).
The IAU, the international organization responsible for such names, has never given them any objective definitions. Why? Because they don't need any. Sorting out terminology like this is almost completely ancillary to getting actual astronomy and astrophysics done. The very reason that those interested in establishing definitions can't agree on objective definitions underlines the point: because they are totally arbitrary and not very important.
Almost all of the furor about redefining terms, recategorizing objects, demoting planets and promoting asteroids, has come from amateurs and the popular media. Don't you think that if professional astronomers thought that this was such a crucial issue that they wouldn't have taken care of it handily? They haven't because it's not nearly as important as amateurs seem to think. That amateurs and the popular media are seemingly fixated on such trivialities indicates strongly to me that they're missing something: namely that these classifications have no external significance.
The map is not the territory. Give it a rest, already. I know, why doesn't everyone concentrate their energies on doing actual astronomy?
If a planet gets kicked out of its orbit (unlikely now, but during planet formation it's surely possible), it would stop being a planet?
"It's too bad that stupidity isn't painful." - Anton LaVey