quote: SCIENTISTS are getting set to expand our solar system by adding three new planets, taking the number from nine to 12 and changing what children around the world are taught about our corner of the universe.
The International Astronomical Union, the accepted authority on planetary matters, has recommended to its members that Charon, Xena and Ceres be ratified as new planets, a US newswire service has reported.
quote:The new order of planets going out from the sun would be Mercury, Venus, Earth, Mars, Ceres, Jupiter, Saturn, Uranus, Neptune, Pluto, Charon and Xena.
posted
This redefinition, if it passes, will lead to more confusion, not less. I hope the IAU votes it down. It seems like the type of commitee drivel that will please no one and serve little useful purpose.
Charon is a moon, how can it also be a planet? There are 7 larger moons than Charon: Earth's Moon, the 4 Galilean Jupiter moons, Titan and Triton are all bigger than Charon. Charon does have the highest ratio of a moon to a planet (about 11% of the mass), but it's still clearly the smaller one. http://ssd.jpl.nasa.gov/?sat_phys_par
quote: The new definition, which states that a planet is any star-orbiting object so large that its own gravity pulls in its rough edges and produces a near-perfect sphere,
Umm, Ceres is 975×909 km, not a near-perfect sphere.
I'm cool with calling Xena a planet, it's pretty big and orbits the sun, not another planet.
I'd also be willing to lock in 8 planets (minus Pluto) or 9 plus anything bigger than Pluto. But calling Charon a planet makes little sense.
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posted
Morbo, I think you're right on. Pluto was called a planet for political reasons, because it was the first "planet" candidate to be discovered by an American, among other reasons. Plus, its more likely an escaped moon, as is its own moon.
I would be in favor of an 8 planet chart, including stellar bodies larger than the largest known moon, which orbit the sun on the plane of the ecliptic and in a tight elipse. Pluto has a wierd orbit, is too small, and is probably the closest of dozens or hundreds of similar extra-jovian objects. What happens when we start locating dozens of outer "planets" when they really bare as much similarity to the inner planets as the keiper belt does? What do we call these objects when we start locating them in other solar systems, as we begin to detect planets of less than Jovian mass?
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quote:Charon is a moon, how can it also be a planet?
The issue is that Charon is no more a moon of Pluto(or less one) that Pluto itself is a moon of Charon, and neither can be said to orbit the other. They both orbit a center of gravity that is in space between the two bodies. It is much more a "double planet" than a planet with a moon.
I don't really care if both of them are "escaped moons". If they orbit the Sun, and not a planet they are disqualified from being "moons" in my book. If our moon somehow escaped Earth orbit and started circling the Sun on its own, I'd be all for reclassifying it a planet.
Furthermore, the new definition states:
quote:"A planet is a celestial body that (a) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and (b) is in orbit around a star, and is neither a star nor a satellite of a planet."
There is no requirement of "near-perfect sphere". So what if this leads to a hundred other object that fit the definition coming to be called "planets". In what way does this make things more confusing or difficult? Are we afraid school kids are going to have to recite a list of a hundred planets (along with the dozens of other inane activities many of their classes are filled with)? Is there a problem with referring to the "8 major planets" or the "12 inner planets" if you really have a need for some defined limit?
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I read that Pluto is being considered the prototype of a new type of planet called a "pluton." The idea is that they will still be considered planets, but that they are in a special class.
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quote:Charon is a moon, how can it also be a planet?
The issue is that Charon is no more a moon of Pluto(or less one) that Pluto itself is a moon of Charon, and neither can be said to orbit the other. They both orbit a center of gravity that is in space between the two bodies. It is much more a "double planet" than a planet with a moon.
I'm fairly certain that the same thing is true of Earth and Luna.
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posted
The newspaper article on this in my area doesn't mention Xena by name, but rather a "12th planet that is yet to be named."
quote:I'm fairly certain that the same thing is true of Earth and Luna
Although both masses do pull upon each other and the "center of gravity" is not the center of the Earth, the Earth has sufficient mass so that that center is still within the planet.
Charon, as I can recall, is half the mass of Pluto, so the effects of gravity are much more dramatic.
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posted
Nighthawk is right. The center of gravity of the Earth-Moon system is well within the space of the parent planet (Earth).
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Don't tell this guy. He wrote a book called "The 12th Planet" about an extra-solar planet whose inhabitants are the gods of ancient mythologies. Non fiction, that is.
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posted
What exactly would an "extra-solar" planet be? Until the sun goes all red-giant on us, aren't all the known planets "extra-solar"? [Discounting, of course, planets that orbit other stars. I mean, if it orbits the sun in what way is it "extra-solar" that Earth isn't, for instance?]
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quote:Charon is a moon, how can it also be a planet?
The issue is that Charon is no more a moon of Pluto(or less one) that Pluto itself is a moon of Charon, and neither can be said to orbit the other. They both orbit a center of gravity that is in space between the two bodies. It is much more a "double planet" than a planet with a moon.
I'm fairly certain that the same thing is true of Earth and Luna.
Not really, the center of the earth moon system is inside the earth.
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quote:Originally posted by Nighthawk: The newspaper article on this in my area doesn't mention Xena by name, but rather a "12th planet that is yet to be named."
According to wikipedia, it isn't actually named yet. The designation is 2003 UB313 - Xena is the nickname given to it by astrologists.
And this will make Flyingcow happy - the nickname for 2003 UB313 aka Xena's moon is Gabrielle.
What I found fascinating was the dual tidal-lock between Pluto and Charon (Both always have the same side facing each other - unlike say, the Moon and Earth where only the Moon is gravitationally locked). ( Wiki ). To me that lends more credence to the twin-planet theory (ie Charon isn't just a moon).
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posted
I was typing on the fly. I think I used the term 'extra-solar' to mean a planet that is outside our traditionally understood solar system, that still orbits the sun (according to him, every 3600 years). According to Sitchin, when it does come within the traditional solar system, it passes closely to earth and allows the inhabitants of that planet to interact with humans. They 'made' humans by mixing their DNA with Homo Erectus. They are the Nephilim of old. There was a war between the differing gods that culmunated in some kind of nuclear exchange in the middle east about 3600 years ago. Sitchin deducing these 'truths' from ancient Sumerian legends and projecting modern ideas and word definitions on ancient stories and pictures.
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quote:And this will make Flyingcow happy - the nickname for 2003 UB313 aka Xena's moon is Gabrielle.
I find this hilarious beyond words. A relatively short-lived western tv show during the 90's may be immortalized in naming of a planet in our solar system.
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posted
I wonder how likely that is. I mean, the organization who chooses the name will likely be international and surely not made up of a majority of Xena fans. (Or maybe they are?)
Traditionally, planet names (in our solar system) have been taken from Greek/Roman mythology. I'd rather see them take another name from there, or from another mythology (Odin, Thor, etc) before resorting to contemporary fiction.
On another note, I found this tidbit on Wiki in an article on naming conventions:
quote:Starting in 1801, asteroids were discovered between Mars and Jupiter. The first few ones (Ceres, Pallas, Juno, Vesta) were at first considered minor planets and joined the ranks of the planets. As more and more were discovered, they were soon stripped of their planetary status. Pluto was not considered an asteroid, being found very far indeed beyond any then-known asteroid's greatest distance from the Sun.
So, Ceres was already considered a planet at one point, then demoted, and now stands to be re-instated as a planet.
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quote:Originally posted by KarlEd: I wonder how likely that is. I mean, the organization who chooses the name will likely be international and surely not made up of a majority of Xena fans. (Or maybe they are?)
Traditionally, planet names (in our solar system) have been taken from Greek/Roman mythology. I'd rather see them take another name from there, or from another mythology (Odin, Thor, etc) before resorting to contemporary fiction.
On another note, I found this tidbit on Wiki in an article on naming conventions:
quote:Starting in 1801, asteroids were discovered between Mars and Jupiter. The first few ones (Ceres, Pallas, Juno, Vesta) were at first considered minor planets and joined the ranks of the planets. As more and more were discovered, they were soon stripped of their planetary status. Pluto was not considered an asteroid, being found very far indeed beyond any then-known asteroid's greatest distance from the Sun.
So, Ceres was already considered a planet at one point, then demoted, and now stands to be re-instated as a planet.
whatever! They used dirty greek/latin mythology because their languages were the language of science. They've had their run, lets use something more contemporary now that we have new planets to name. I should note I am not a fan of using Xena as one of the names. Really Kirk or Picard would make for a better name
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posted
In terms of the mythology-naming: I found this quote from Michael Brown, one of the people who discovered Xena/2003 UB313 very interesting:
quote: "If the object falls under the rules for other Kuiper belt objects, however, it must be named after some figure in a creation mythology. We have decided to attempt to follow that ruling scheme. […] One such particularly apt name would have been Persephone. In Greek mythology Persephone is the (forcibly abducted) wife of Hades (Roman Pluto) who spends six months each year underground. The mourning of her mother Demeter causes the dead of winter. The new planet is on an orbit that could be described in similar terms; half of the time in the vicinity of Pluto and half of the time much further away. Sadly, the name Persephone was used in 1895 as a name for the 399th known asteroid
quote:And this will make Flyingcow happy - the nickname for 2003 UB313 aka Xena's moon is Gabrielle.
I find this hilarious beyond words. A relatively short-lived western tv show during the 90's may be immortalized in naming of a planet in our solar system.
Absolutely not. Planetary Astronomers are rather mad at Mike Brown for even promoting the name Xena, since it flies in the face of all the conventions set down by the IAU for naming minor bodies. When the IAU votes to name the planet and its moon, it will not be Xena or Gabrielle.
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quote:Originally posted by IanO: Don't tell this guy. He wrote a book called "The 12th Planet" about an extra-solar planet whose inhabitants are the gods of ancient mythologies. Non fiction, that is.
That's a matter of opinion.
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quote:And this will make Flyingcow happy - the nickname for 2003 UB313 aka Xena's moon is Gabrielle.
I find this hilarious beyond words. A relatively short-lived western tv show during the 90's may be immortalized in naming of a planet in our solar system.
Absolutely not. Planetary Astronomers are rather mad at Mike Brown for even promoting the name Xena, since it flies in the face of all the conventions set down by the IAU for naming minor bodies. When the IAU votes to name the planet and its moon, it will not be Xena or Gabrielle.
I don't understand. Xena turned out to be Ares' daughter, no? That makes her part of the Greek pantheon. And Gabrielle... well, do domestic partners count? <grin>
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posted
I still vote for Xena and Gabrielle for planet names.
What are the other planets named for but characters from stories? (well, ok Gods people worshiped. Never the less... stories.)
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I am familiar with the double planet arguement for Charon, but don't find it compelling. All moons, in general terms orbit around the center of gravity of their planetary systems--whether the COG is in the primary or not shouldn't be the defining characteristic of "moonishness".
The mass of Charon is estimated to be between 8% and 15% of Pluto according to a webpage I saw last night, Nasa said 11%. It's clearly the smaller object.
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According to Wiki (can't add link because link contains parentheses):
quote:Charon's diameter is about 1,207 km (750 miles), just over half that of Pluto
quote:Charon has approximately 11.65% of the mass of Pluto.
They're rather hard pressed to consider Pluto a planet.
quote:Charon has been a part of the controversy over Pluto's status as a planet. Under the latest proposal, which will be decided on August 24, 2006, the International Astronomical Union may classify Charon as a pluton, officially making Charon a planet. Under this proposal, Charon would be considered a binary planet with Pluto since the two orbit each other around a center of mass that is outside either body.[4] Those who have argued against Pluto as a planet consider the two as the first discovered trans-Neptunian objects.
Personally, yes, I consider Charon a moon. But these science guys know more than I do.
*EDIT*
Pluto's Wiki:
quote:Pluto and its satellite Charon have often been considered a binary planet because they are more nearly equal in size than any other planet/moon combination in the Solar System. Under the aforementioned planet definition proposal, since they orbit each other around a center of mass that is outside either body, they would be officially considered a binary planet system.[2]
posted
Morbo: But if the center of gravity is somewhere between the two bodies, then how do you determine which one is orbiting the other? Traditionally, a moon orbits a larger body. That's not the case with Pluto and Charon.
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posted
The whole notion of one 'orbiting' the other is just a human-imposed perspective. They both orbit their combined center of mass, neither orbits around the (center of mass of) the other.
However, I do think the colloquial definition of one body orbiting another is most definitely in line with situations where the combined center of mass is within one or the other object.
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Just for the record, even though MightyCow's name is remarkably similar to mine (though he joined the forum five years after I did), we are not the same person.
It's either a remarkable coincidence, or an homage... or an attempt at identity theft.
I'm going with option 1... for now.
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posted
I've always had something of the idea that Charon is pushing the definition of moon. In pretty much all the existing textbooks something of that is explained, it's just not very official.
I guess that makes me very accepting of the idea of "Pluto-n-Charon". I actually rather like the idea of our solar system having a double planet. It makes things more interesting.
posted
fugu said it well: in any two body system, both orbit around the common COG.
Suppose an new outer system planet-moon combo is discovered. It could be many decades after their discovery before it is definitively determined where the COG is located. What if the COG hovers right at the boundary of the primary? It could even dip in and out of the of the primary's surface as the irregulaties of the primary rotate. Would that make it a moon one moment, and a planet the next?
Would you call it a planet-moon system? A planet with a moon or planet to be determined later? You could have to wait decades to categorize it. Simpler to call the primary the planet (if it's large enough), the other the moon.
posted
Pluto is totally a planet. Just because the shape of its orbit is funky doesn't mean it's less of a planet. Uranus' axis of rotation is perpendicular to its plane of revolution around the sun, which is not true of any of the other planets, yet it's still considered a planet. Charon should be a planet too, if it's true that they both revolve around a point outside of either one of them. Just doesn't make sense to call it a moon. And I think it'd be awesome if Ceres and 2003 UB313 were re-classified as planets. Who cares if that makes it harder to list off all of the planets in our solar system? It's hard to memorize all of Jupiter's moons, too, but that doesn't mean we're just going to re-categorize all of the moons but the Big Four as, I don't know, extra-large ring dust or something. Anyone who really wants to memorize the names of the moons of our solar system (all right, it was fifth grade, I had nothing better to do) can just stick to memorizing the major ones; same with the planets. ("And these were the nine historically recognized planets we had before we decided that we should let in more Kuiper Belt objects, class.") And as far as the name "Xena" goes...shouldn't moons be named after Greco-Roman mythological characters also? Yet although we follow that pattern with Ganymede and Io and Rhea, we've also got Titania and Miranda floating around Uranus, which is a little more modern than that. So either scratch Shakespearean names off of the list, or allow a little more pop-culture, darn it! (And if we ever find a planet populated by headless immortal aliens with a light red atmosphere and red trees, I call dibs on naming it "Planet Claire" after the B-52s song.)
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1) Chouldn't we just combine Pluto/Charon into a single planet, that happens to be divided by some space? We could call it, after Pluto--Goofy.
2)What do you mean Xena is fiction. I thought the show was a true portrayal of ancient Greek life.
3)Why not auction off the names of the planets. After all, its all about the Merchandising. If its good enough for the Milky Way and Mars candy bars, its should be good enough for us.
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posted
The problem with the Greco-Roman mythological characters is that the IAU is out of names. Most of the good potential names got used on either Asteroids or moons and they don't feel they can reuse names, especially because the good names belong to the first Asteroids discovered. Nobody in the IAU except Mike Brown wants the names Xena and Gabrielle.
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I don't know why there is so much importance being placed on whether the COG or barycenter is within the primary or not. To me it's extraneous to a moon definition and adds little. The planet is the primary, anything smaller is a moon.
If you're going to upgrade Charon because of it, shouldn't you upgrade Jupiter to a co-star or super-planet? I suspected the COG of the Jupiter-Sun system is outside of the sun's surface, and according to wiki it is:
quote:Sun-Jupiter system: put Sun in position 0, mass = 333,000 Earths. Jupiter in position 778,000,000 km, mass=318 Earths. Center of mass is 742,000 km from the Sun center, 46,000 km outside its surface. As Jupiter does its 12 year orbit, the Sun does a 1.5 million km orbit around the center of mass.
posted
It's not that they don't want them; they didn't even submit the names "Xena" and "Gabrielle" as options to the IAU.
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quote:posted by Morbo: All moons, in general terms orbit around the center of gravity of their planetary systems--whether the COG is in the primary or not shouldn't be the defining characteristic of "moonishness".
Why not? It sounds like a perfectly reasonable method of determining "moonishness". Since we're (and by "we", of course, I mean "they") deciding on a definition, it's going to be arbitrary. The best we can do is set up terms that will lead to the most clarity.
From your arguments regarding Pluto's and Charon's relative masses, should I take it that you think size should play a central in the matter. Why do you think this to be a better definition? Should we have minimal size requirements?
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quote:Anyone who really wants to memorize the names of the moons of our solar system (all right, it was fifth grade, I had nothing better to do) can just stick to memorizing the major ones; same with the planets.
Sixth grade. Think we might be distantly related? I never imagined that there was anyone else in the world as obsessed with moons as I was.
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posted
Can't they just move on to Greek names instead of Roman ones, or possibly Norse or Egyptian or whatever? Why are we stuck with just Roman mythology?
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We need a minimal size requirement because the number of known asteroids is in the five digits. We can't call every ice potato that orbits the sun a planet. Some Astronomers wish Pluto was considered an ice potato- that's where the size thing comes in- big enough not to be a potato is what the new definition says. But Pluto is more than a chunk of ice- it's a chunk of ice with a tenous atmosphere, a nother planet (however small) and two moons.
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Asteroids aren't ice potatoes; that's comets (and there's some rock involved). Jupiter couldn't be a co-star because it's not a star.
I've been following this debate over at Whatever between Jon Scalzi and Scott Westerfield. To quote a (male) comment-er in a thread over there:
quote:Personally I love that the question is all about size. Yes, there are (a sizeable number compared to other fields of) female astronomers out there but it’s still an old mans club. And having old (geeky) men argue about the size of things relating to their importance just makes me all snickering inside.
(hat="snark") Now Jupiter, by Jove, there’s a planet. Big, massive and fully rotund. He’s got a whole bunch of attendants circling around (say, any of Jupiter’s moons named for male Greeks?) paying close attention, circling close, caught in the gravity of the situation. Big Van Alan belts, you betcha, reaching out and caressing those little moons. Now THAT’S a planet, if you know what I mean.
Then there’s this Pluto. Little puny thing. Not exactly on the level, if you know what I mean. Highly irregular. Has these other guys hanging around. You know what they say. (/hat)
I just get a smirk on my face every time I think about that argument. Say, how many of the IAU members drove here using a car with manual transmission?
If you look at size comparisons, the only reason why Earth/Terra isn't just considered a large asteroid has nothing to do with size (compare the terrestial planets with the gas planets, please, then wonder why there's such a fuss over the dwarf planets being so small); it's because we live on it. Very...human-centric.
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