Vesta Is a Baby Planet, Not an Asteroid 107
astroengine writes "Vesta, the second largest object in the main asteroid belt, has an iron core, a varied surface, layers of rock and possibly a magnetic field — all signs of a planet in the making, not an asteroid (abstract). This is the conclusion of an international team of scientists treated to a virtual front row seat at Vesta for the past 10 months, courtesy of NASA's Dawn robotic probe. Their findings were presented during a NASA press conference on Thursday. As to why Vesta never made it to full planethood, scientists point to Jupiter. When the giant gas planet formed, nearby bodies such as Vesta found their orbits perturbed. 'Jupiter started to act like a spoon in a pot, stirring up the asteroid belt and the asteroids started bumping into one another,' said Dawn lead scientist Christopher Russell. 'If they're just out there gently orbiting and everything is going smoothly, then without Jupiter in the picture, they would gather mass and get bigger and bigger and bigger. But with Jupiter there, stirring the pot, then the asteroids start bumping into one another and breaking apart, so nothing grew in that region, but started to shrink.'"
Pluto? (Score:5, Interesting)
So Pluto was deemed just another large chunk of space debris orbiting the earth, and hence not a planet. Vesta *is* just a large asteroid amongst a whole bunch of others, but it is a planet?
I'm confused now.
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Planets orbit the sun, asteroids orbit something else. If a rock among other rocks is orbiting the sun, and it meets the other qualifications, it's a planet..
No. Asteroids orbit the sun.
A spherical object orbiting the sun and has cleared its orbit of other large objects is a planet.
Pluto Takes Out Neptune (Score:2)
So.. if Pluto takes out Neptune.. can it be a planet.. seeing as it cleared its orbit ?
Re:Pluto Takes Out Neptune (Score:4, Funny)
And if a group of pro-Plutoans happen to make Neptune...disappear...does Pluto still get planetary status?
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They seem to be saying it's in an asteroid belt... which implies it didn't clear it's orbit? I'm asking not telling... I really have no idea. I'm still shocked pluto lost it's title... mostly because it was named Pluto which in the context of the other planet names is fitting. If we start naming the new planets with a different convention it will be annoying.
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Planets orbit the sun, asteroids orbit something else. If a rock among other rocks is orbiting the sun, and it meets the other qualifications, it's a planet..
How could someone so obviously clueless about the makeup of our solar system feel compelled to comment on that post?
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How could someone so obviously clueless about the makeup of our solar system feel compelled to comment on that post?
How could someone so obviously clueless about the makeup of Slashdot feel compelled to comment on that comment?
Re:Pluto? (Score:5, Informative)
The abstract specifically says that Vesta is not an asteroid. When Ceres was reclassified as a dwarf planet, there was some question about Vesta, because it's not a proper spheroid. The question is: was it deformed by external forces or was it just never able to form a proper spheroid?
Since "baby planet" is not a proper IAU category, I think this means either A) it's a dwarf planet, like Pluto or Ceres, or B) the question is still open, but we've learned something new about its origin--a completely separate matter.
I think the IAU definitions are extremely silly, but I also think it's extremely silly think that Pluto is special, or any more deserving of planet status than Ceres, which was not considered a planet for many, many years. Personally, I'd rather see a definition of planet that includes Ceres and excludes Pluto than the reverse. (Though I'm also open to a definition that includes Ceres, Pluto, Luna, Ganymede, Titan, and more.)
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Just like the term 'star' actually covers a huge range of objects with some basic similarities (fusion-driven radiation emitters), so does the word 'planet'. We have terrestrial planets, ice giants, gas giants, ice dwarfs, and now apparently surviving protoplanets like Vesta.
Re:Pluto? (Score:4, Insightful)
(fusion-driven radiation emitters)
That doesn't seem to work for white dwarf stars.
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(fusion-driven radiation emitters)
That doesn't seem to work for white dwarf stars.
No more (planets) for the dee-warf.
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But that does get into the issue of "brown dwarfs" where fusion hasn't started, trying to distinguish them from objects like Jupiter.
Calling a "star" something that has actual fusion going on in its core should be sufficient to distinguish it from other smaller mass objects.
Besides, in the cosmological zoo, you could call white dwarfs kind of their own type of beast with its own unique area of classification. The problem with Vesta is that there has been some silly attempt to define a planet with a helioce
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But that does get into the issue of "brown dwarfs" where fusion hasn't started, trying to distinguish them from objects like Jupiter.
Calling a "star" something that has actual fusion going on in its core should be sufficient to distinguish it from other smaller mass objects.
How about calling a "star" something that has or had actual fusion going on, thus distinguishing it from anything that was never massive enough to fuse hydrogen.
A white dwarf is a stage in the post-fusion life of a star that wasn't massive enough to become a neutron star, but like a neutron star becomes a form of degenerate matter -- there's no reason to call one a star and not the other. It is nothing like a brown dwarf where it really is a matter of degree that separates it from jupiter, not kind.
Besides, in the cosmological zoo, you could call white dwarfs kind of their own type of beast with its own unique area of classification.
Includi
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I'm ragging on a faulty redefinition when previously there was none at all, other than a convention of simply calling the largest objects in the Solar System "planets".
For myself, I could care less if you call Pluto a planet or not, and in a way I look at the IAU definition as sort of "promoting" Ceres instead to be recognized as a planet and something unique instead of just being another asteroid. Vesta and Pallas fit into this sort of "promotion" category as well. The earlier description wasn't really a
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other than a convention of simply calling the largest objects in the Solar System "planets".
... Except not... Conventionally, bodies which constituted only a small proportion of the total matter in their orbits were not considered planets but rather one asteroid in an asteroid belt or trojans captured by an obviously dominant body -- the planet. The model of the solar system and list of planets you and I both learned as kids was based on this premise.
Funny how you don't care if Pluto is a planet but your incorrect recollection of the conventional, uncodified definition is one where Pluto would s
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... Except not... Conventionally, bodies which constituted only a small proportion of the total matter in their orbits were not considered planets but rather one asteroid in an asteroid belt or trojans captured by an obviously dominant body -- the planet. The model of the solar system and list of planets you and I both learned as kids was based on this premise.
That isn't exactly true. The model of the solar system from about 40 years ago (to pick an arbitrary date meaning at the beginning of the "space age") was mainly the big stuff, with asteroids treated as a special class of stuff. Dominance in their orbits had absolutely nothing to do with how they were defined, and in fact a "planet" really was whatever you could see in the sky that wasn't a star. They were really just big things.
Uranus, Neptune, and Pluto were treated as big things that weren't asteroid
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Titan does not orbit the sun directly...
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Titan does not orbit the sun directly...
Neither does "Luna"... *
*some might argue it is a double planet system, in which case, I withdraw my snarky comment
Well, if the Earth is a double planet system, then Pluto and Charon even more so would be a double planet system, considering at least that the point of rotation in the Earth-Moon system is located within the Earth, while Pluto-Charon orbits around a point in open space...
Note that I did not mention any of the other planetoids specifically because I only needed on counter example. And "Luna == the Earth's moon" is kind of weird nomenclature for me. (Yes, I do know it's correct, but still.)
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Pluto+Charon are a double dwarf planet system. On the other hand, I would call Luna (more correctly... The Moon, which is its proper Anglo-Saxon name) a dwarf planet as well.
If there is a term to be depreciated, it would be "moon", other than in connection with objects orbiting inside of the Hill sphere [wikipedia.org] of a non-stellar body. A better term would be satellite, other than the fact that "artificial satellites" seem to have taken on the term. An object orbiting another object which is in turn orbiting a 3rd
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Pluto+Charon are a double dwarf planet system. On the other hand, I would call Luna (more correctly... The Moon, which is its proper Anglo-Saxon name) a dwarf planet as well.
Except by that definition, then the Earth has not cleared its orbit...
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Except by that definition, then the Earth has not cleared its orbit...
Neither has Jupiter, Saturn, or Mars, and arguably Neptune as well. Even Uranus has "large planetary-like objects" near it.
Is Venus genuinely the only real planet in the Solar System?
That is why the whole notion of clearing out the orbit is as silly as any other part of the IAU definition.
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Except by that definition, then the Earth has not cleared its orbit...
Neither has Jupiter, Saturn, or Mars, and arguably Neptune as well. Even Uranus has "large planetary-like objects" near it.
Is Venus genuinely the only real planet in the Solar System?
That is why the whole notion of clearing out the orbit is as silly as any other part of the IAU definition.
Except "cleared its orbit" does not include any satellites, and also does not include small masses (non-planetoids). So, my definition has no problem with downgrading everything except Venus, because the satellites do not count. However, if you consider Luna/The Moon as a dwarf planet, now you have the Earth in an orbit with a dwarf planet, and thus no eligible for the "planet" nomenclature.
My definition doesn't have a problem... sure it's arbitrary, but it doesn't have a problem. Your alternatives however
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You are presuming that I'm trying to define a planet with the notion that clearing out its orbital path is a prerequisite. I'm suggesting that the whole notion is absurd in the first place that it should even be a part of the definition. Orbit clearing is simply not even necessary to be in the definition. Then again I'm also suggesting that the heliocentric definition by the IAU is just as absurd as it requires that planets also must orbit the Sun, and any object which does not orbit the Sun is thus not
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even if it happens to orbit another star or simply orbits the center of the galaxy.
Hmm... [tinypic.com]
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You are presuming that I'm trying to define a planet with the notion that clearing out its orbital path is a prerequisite. I'm suggesting that the whole notion is absurd in the first place that it should even be a part of the definition. Orbit clearing is simply not even necessary to be in the definition. Then again I'm also suggesting that the heliocentric definition by the IAU is just as absurd as it requires that planets also must orbit the Sun, and any object which does not orbit the Sun is thus not properly called a planet... even if it happens to orbit another star or simply orbits the center of the galaxy.
Except the "heliocentric" IAU model makes no such claim. The IAU classification system only applies within the Sol System. Extending it outside the Sol System is as easy as: "orbits the stellar mass(es) directly" instead of "orbits the Sun directly".
More specifically and pedantically, the exact IAU text bolded for emphasis:
The IAU...resolves that planets and other bodies in the Solar System be defined into three distinct categories in the following way:
This is clearly interpreted as: "the IAU is making rules about the Solar System, and the Solar System only, these rules do not apply outside of the Solar System."
Beyond the IAU specificat
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Titan does not orbit the sun directly...
Wow, really? :)
And would change what we call it change that? Why should orbital characteristics be a factor in planethood at all? Of course, calling it a planet won't make it stop being a moon of Saturn. By why should it only be known as a moon? There are plenty of moons that couldn't meet the definition of dwarf planet (let alone planet) even if they did orbit the sun directly. Phobos and Deimos, for example. Why not say that Titan is both a small planet and a moon of Saturn?
What would you call a lar
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Stars are round and big enough to trigger fusion. ... What's wrong with that definition?
Firstly what is wrong, is that there are stars that do not undergo fusion...
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Firstly what is wrong, is that there are stars that do not undergo fusion...
If you mean brown dwarfs, I'm open to tweaking the definitions to fit them in in either category, though I'd personally tend towards categorizing them as planets. If you're referring to ex-stars, I was glossing over that for simplicity's sake. Let's say, round and big enough to have triggered fusion at some point. Or you could simply call them ex-stars. :)
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Or you could simply call them ex-stars.
Why multiply terms unnecessarily?
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One person's unnecessary distinction may be another person's critical distinction. I don't have a strong preference myself, so I prefer to let those who care fight it out. Hence my use of the word "or". :)
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Firstly what is wrong, is that there are stars that do not undergo fusion...
If you mean brown dwarfs, I'm open to tweaking the definitions to fit them in in either category, though I'd personally tend towards categorizing them as planets. If you're referring to ex-stars, I was glossing over that for simplicity's sake. Let's say, round and big enough to have triggered fusion at some point. Or you could simply call them ex-stars. :)
Interesting question... does the fusion have to be natural? How would we distinguish natural from "unnatural"? And what if something had fusion for a very brief moment.
As an example, the Earth has had a few naturally-occurring fission reactors in its history... if the Earth ever had a fusion event naturally by your standards it would then be a star or ex-star...
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Man, what are you on about? I'm not trying to define "star". I think the current definition is probably fine. I only mentioned an oversimplifed definition to contrast with my proposed definition of planet. If you've got a problem with the definition of star, talk to an astronomer. If you've got a problem with my proposed definition of planet, then I'm the one you should be pestering. :)
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Re:Pluto? (Score:4, Interesting)
I'd rather see a definition of planet that includes Ceres and excludes Pluto than the reverse.
I don't see what would put Ceres and Pluto in different categories under any system. Neither has cleared its orbit (I too think this is a silly criterion.) Both have the hydrostatic equilibrium thing going. Both orbit the sun directly.
Well, there *is* one peculiarity about Pluto: the barycenter of the Pluto-Charon system is outside both. While I dislike the clear the neighbourhood criterion I think this system is actually the strongest proof of the current planet definition being temporary: Pluto-Charon is a binary (dwarf) planet, yet no one has bothered to even mention Charon. Instead one of our current dwarf planets orbits an empty piece of space.
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I don't see what would put Ceres and Pluto in different categories under any system.
How about composition and origin? Ceres is a rocky object, similar to Mercury or Io. Pluto is a giant snowball--basically a big-ass comet. Ditto for Eris, which isn't subject to your objection about its binary-system status.
Neil DeGrasse Tyson uses the "Pluto is just a big comet" as one of his main excuses for defending the decision to stop calling Pluto a planet. Well, guess what? That doesn't apply to Ceres. But it is still an important distinction between Pluto and all the objects we historically
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Of course, if you're going by compositional similarity, then putting Mercury and Jupiter in the same category is also silly. Which is why my preferred solution is to make "planet" a super-category that includes 1) gas giants, 2) round rocky objects, and 3) round comet-like objects. I wouldn't bother to mention orbits at all. Orbital characteristics should be part of a separate classification system, IMO.
I agree completely about the super-category part.
I wouldn't change the orbit definition, mostly because another huge can of worms would be opened then. : )
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I don't see any can of worms. You can still get a fairly traditional list by referring to "planets which orbit the Sun" to distinguish from planets (like Luna and Ganymede) that orbit other planets. You can also distinguish planets in the core system from planets in the Kuiper belt.
Adding orbital characteristics is what seems to open a can of worms to me. Suddenly all sorts of things that are identical to planets in any reasonable respect (like "rogue planets") lose that classification. To what end? N
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Well, there *is* one peculiarity about Pluto: the barycenter of the Pluto-Charon system is outside both.
While the Pluto/Charon system has a barycenter outside Pluto's surface, it's so much closer to Pluto that it would be wrong to consider them a binary system more any more than the Sun/Jupiter system is a binary system. Remember that barycenter of Jupiter and the Sun is also outside the sun - that doesn't make us demote the sun or promote Jupiter from planet status to stellar companion.
Instead one of our current dwarf planets orbits an empty piece of space.
I'll bite. Which one? Mercury? But it has planet status.
No other small object really has a clear orbit.
Re:Pluto? (Score:5, Funny)
It's not a baby planet, it's not a dwarf planet. It's a proto-planet stuck in proto- state due to Jupiter.
I like to think of it as an aborted planet.
Obviously we need to outlaw Jupiter to prevent further proto-planet abortions.. Furthermore, we need full funding of a federal agency to ensure Jupiter isn't available to all wanton sinners who would otherwise bring a planet to full term.
Well, folks, seems to me like we finally figured out how to ensure NASA's budget isn't axed.
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For an object of that size to have an iron core means it is the debris of another planet. Simply insufficient mass to allow gravity to maintain a inner molten state and promote the refinement of iron from the collection of accumulated dust.
Sure it's an very old chunk of debris that over the aeons has accumulated new layers of dust, but it hardly is a proto planet, wrong type of core.
So pieces of Vesta found on earth on pieces of the planet Vesta was once a part of found on earth. Astronomers so hate ca
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So basically Vesta is Earth's aborted little sister.
Oh great, give the Republicans another excuse to cut science funding.
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Um, the summary says it might have become a planet, but didn't.
So basically Vesta is Earth's aborted little sister.
Pluto on the other hand is a "dwarf planet" which is presumably something like the lazy uncle's helper monkey.
Well, Vesta is proably more like Ceres dwarf fraternal twin sister than Earth's (shared the same rough orbital distance or "womb" as Ceres, but didn't quite make it to planet status and became a dwarf twin to a dwarf planet). Basically one princess would have to kill the other princess to clear out the orbit/castle to become the queen of the orbit and become a planet. Unfortunatly, the chaotic life that they lead in the same castle (like prince charles and camilla) and the influence of a powerful royal in
Re:Pluto? (Score:5, Interesting)
No, what they have found, and what makes this newsworthy, is that Vesta's composition is much more like the terrestrials (Mercury, Venus, Earth, Luna, Mars) than what they believe Ceres' composition is. They now believe that Vesta belongs to the terrestrial family, having a silicate rock crust/mantle surrounding an iron core. Ceres, on the other hand, is probably made primarily of an ice crust/mantle with a rock core, putting it in the same family as the moons of the gas giants, and the Kuiper Belt objects like Pluto. So while Ceres and Vesta live in the same castle, they are adopted from different families.
They will know more when Dawn leaves Vesta and visits Ceres, though.
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So while Ceres and Vesta live in the same castle, they are adopted from different families.
Since they probably were both "conceived" from matter from the same protoplanetary disc, it's might be considered more akin to Heteropaternal superfecundation, than adoption from different families (which might imply that one of them came from another star system and was "captured" in that orbit).
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Probably needs to be confirmed and voted on before they can change it's official certification from asteroid to dwarf planet.
i'ts not that complicated (Score:2)
http://upload.wikimedia.org/wikipedia/commons/9/91/EightTNOs.png [wikimedia.org]
in the last decade, they started to find a lot more plutos. so the question is do we have 10, 16, 54 planets? or do we say "look, pluto doesn't really fit the idea of something large that controls its orbit, so it's not a planet" and so we only have 8 planets
it's a perfectly good decision
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...space debris orbiting the earth...
Wait, Pluto orbits the Earth now?
Re:Pluto? (Score:5, Funny)
Wait, Pluto orbits the Earth now?
Everything orbits the Earth. Heliocentrism is a fraud, brought to use by the same "scientists" as evolution, global warming, and that dubious round-earth theory. :p
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Wait, Pluto orbits the Earth now?
Everything orbits the Earth. Heliocentrism is a fraud, brought to use by the same "scientists" as evolution, global warming, and that dubious round-earth theory. :p
Exactly! Everyone knows that Pluto orbits in an epicycle [wikipedia.org]!
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No one is saying that Vesta *is* a planet *right now* rather, that Vesta is a planetary core capable of acting like a seed and become a planet by clearing its orbit, if only Jupiter wasn't there. So, no, Vesta is no planet, but it's no mere asteroid, that's why they called it a "baby planet"
Pluto wasn't "demoted" from planet to asteroid. It was moved into is category of plutoids because it is not the "only pluto" in our solar system, nor the only pluto in Pluto's orbit.
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I don't know if it's a planet or not and I don't care. I do know that it's a rather valuable hunk of useful stuff, in a useful place and condition. More than enough metals there to be a near-zero-G spacedock.
Vesta's worth nowhere near as much as Ceres. When Dawn gets to 1 Ceres, that's when the gold rush begins. Ceres has more water on it than all the fresh water on Earth, and other volatiles as well. It's a grand fuel depot for exploitation of the asteroid belt.
Considered together they're wealth b
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Curse nature for not conforming to our nomenclature!!!
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Curse you nomenclature for not conforming to nature.
Wait a minute... I thought that was called science.... or something like that.
Weird analogy (Score:1)
And it's a Good Thing (tm) (Score:5, Insightful)
That would have turned Mars into an asteroid belt ... and Earth into an undersized Mars.
And since Venus is just too darn close to the sun to support life ... another lifeless solar system.
"history is written by the victors" (Score:3)
it's a cynical quote, because it's not really true: principles actually define winners and losers
but it certainly applies to planet formation
Re:And it's a Good Thing (tm) (Score:5, Interesting)
Are you sure about that?
My astronomy is rusty, but I seem to recall that the inner planets are rocky because their proximity to the sun meant they were unable to build up the kind of atmosphere the gas giants did: their atmospheres boiled off before they could grow to the mammoth proportions of the gas giants.
Given the distance from the sun to Cerers, would Ceres ever have been able to form into a gas giant?
Anyway, who's to say Jupiter (or at least its moons) are lifeless? :|]
Re:And it's a Good Thing (tm) (Score:5, Informative)
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"Hot Jupiters" are thought to have formed in an outer orbit, and then migrated inwards, perhaps by being perturbed by another passing star. It is highly unlikely for a gas giant to form that close to a star, but very likely for a planet's orbit to be jostled by something passing by.
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Or their orbit could just be unstable. They could be spiraling into their sun with each revolution, but we'd never know, since it'd take too long to actually cause our measurements to change.
But based on these recent observations, the fact that Jupiter hasn't swallowed up all of the inner rock planets in the past 4.5 billion years is fairly unusual..It very well could be that if the asteroid belt had coalesced into a planet (there's certainly enough material to do so), perhaps Jupiter's orbit would be desta
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...
Anyway, who's to say Jupiter (or at least its moons) are lifeless? :|]
God. He owns the copyright on Life and only allows it on Earth.
He fights Satan, the evil anti-copyright hippy with his zombie son.
Anyways, he only created Life 6k years ago, so obviously the science is all wrong.
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As Solandri said various theories for organization of planets around a star - terrestrial and gas giant - are plentiful. None of them have much weight given recent extrasolar observations. Ceres would never have formed a gas giant unless it was present so early in the presolar cloud that its gravity attracted a huge fraction of the gases present, and obviously some other mass did that first, and that mass was too late to participate in most of the free gas mass - but early enough to gather up quite a bit.
nice try, planetary scientists (Score:4, Funny)
You think this bone you're throwing to Vesta is going to make us forgive what you did to poor Pluto?
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They made a bad call on Pluto, but they're trying to get it right with Vesta, they must be referee-like.
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And why does clearing an orbit of debris mean anything, and how do that help in describing a planet in another star system?
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Oh piffle. The real mistake was back when they decided to classify poor Ceres as an asteroid. The whole nonsense about Pluto appears to be nothing but fallout from that earlier mistake, compounded by a reluctance to grant Ceres the full planetary status it so richly deserves. Ceres is more like Mercury than Mercury is like Jupiter or Pluto.
The old list you learned which included Pluto but not Ceres was simply arbitrary, wrong, and stupid. The current classification is certainly no worse, and is arguably
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Ceres couldn't clear its orbit, therefore it's not a planet. It's just another member of the asteroid belt, a collection of rocks that while had the chance to become a planet, didn't become one. Making Ceres or Vesta a planet would make us forget about all the mass that exists in the same orbit: the asteroid belt doesn't contain a planet, the whole belt itself is a failed planet.
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I HATE the 'cleared its orbit' definition that the IAU came up with. It is an absolutely meaningless definition. Jupiter, which no one will argue as to whether or not it is a planet, has not cleared out its orbit. There are thousands of objects that share the same orbit as Jupiter around the sun, known as the trojan asteroids. Jupiter, with all its mass, will never clear those objects out of its orbit as they are perfectly stable due to the physics of the Lagrangian points.
The pluto decision was purely a po
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What the IAU couldn't handle was promoting the Galilean satellites of Jupiter to the status of planets (along with Titan and Triton and the Moon). If they would have avoided a heliocentric definition for planet, all of those bodies would have been called dwarf planets along with stuff like Pluto.
Yup... dozens of planets (plural dozens). Like this list of objects in the solar system: http://en.wikipedia.org/wiki/List_of_Solar_System_objects_by_size [wikipedia.org]
That is 41 objects larger than 350 km in diameter, clearly
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Ceres couldn't clear its orbit, therefore it's not a planet.
Only if you accept the rather silly requirement that something clear its orbit before being considered a planet. In another system with a lot more debris, it's possible that an Earth-sized planet couldn't clear its orbit, especially if there were interference from nearby super-Jovians keeping things in a state of flux.
It's just another member of the asteroid belt
No it's not. There's a reason Ceres isn't classified as an asteroid. There's a reason it's classified as a dwarf planet. (Though the whole idea that a dwarf planet isn't a planet is nomcla
Soo small (Score:1)
Please keep Baby Vesta safe! (Score:4, Funny)
Dr. Neil deGrasse Tyson on killing Pluto: 'All I did was drive the getaway car'
http://www.theverge.com/2012/3/26/2903224/dr-neil-degrasse-tyson-killing-pluto-on-the-verge [theverge.com]
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How sad:
http://images4.wikia.nocookie.net/__cb20060827052916/uncyclopedia/images/b/bd/Save_pluto.jpg [nocookie.net]
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The current "imperial" system of measurement does not keep America "years behind other countries". It just is something different, and complaining about the lack of conversion to the metric system is just silly. America was able to industrialize without the metric system, which seems to be something remarkable for some weird reason.
Besides, there are good reasons to have a unit divisible by 12 instead of 10, as dividing something into thirds and quarters is much, much easier in base 12 than base 10. Baby
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I don't know of any major American institution that sticks with imperial units with perhaps the exception of rocket propulsion engineers, who still stick with ISP mesurements in seconds (being pound-seconds of thrust per pound of mass). Guess what... most rocket scientist outside of America report their thrust efficiency in seconds as well.
I don't understand your argument. The second is a perfectly valid SI unit. It's a base unit in fact. And you even use the same definition; those rocket scientists use the SI second for specific impulse. (As opposed to one of the other possibilities).
This is a better example of a unit you didn't manage to screw up than one where we show inconsistency, than anything else...
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Specific impulse is not properly defined in seconds... or did you get the "pound-seconds per pound" issue? In SI units, it would be "Newton-seconds per kilogram", which does not reduce to seconds in terms of the units being properly used. The problem here is that a pound is simultaneously a unit of force and a unit of mass, which is one of the reasons why people using imperial measurements typical use a "slug" when trying to perform mass measurements... to keep absurd units like seconds of specific impuls
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Nope. Pound is not both a unit of weight and a unit of force. The two are as distinct as the Newton and the kg. That you use the same sounding name for both of them doesn't fundamentally alter that fact.
Now, there are two ways of specifying specific impulse, one is to base it on the mass of the fuel, then you end up with a Isp as a velocity. If you use weight, you get a time. In either case the conversion factor is 'g' regardless.
This is *exactly* the same regardless of which system of units you work in. Th
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Pound is not both a unit of weight and a unit of force
Sorry, typo. Meant "weight/force and mass"...
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The proper SI unit for specific impulse is meters/seconds^3. That isn't an acceleration unit but something else entirely. In terms of why "seconds" is used, it does get to the "pound-seconds per pound".
Yes, it is some hand waving, and it isn't even a proper way to reduce the units, but it is used. Regardless, the "seconds of impulse" are based around pounds of force and mass as measured in pounds (even if a pound isn't properly a unit of mass). If the values were measured with Newtons and kilograms, you
Re: (Score:2)
Any appeal to pure logic for why SI is better than any other system is like trying to justify a political position or for that matter more akin to theology than anything else.
That's the heart of the matter isn't it? And I don't agree. That's a bit like saying that "well, the Japanese seem to do well with their way of writing, so it*s obviously equal in ever way when it comes to performance compared to the alternatives. (Hint; It's worse in many ways). Or, "Well all sufficiently semantically advanced programming languages are Turing complete, and hence it doesn't matter whether we write this is Brainfuck or Haskell. They're equivalent". (No, the similarities when it comes to util
Re: (Score:2)
Pluto is Greek.
So despite years of denial... (Score:2)
...the asteroid belt IS a failed planet after all?
If so, then it demonstrates why Real Scientists (not ones that kill cute puppies like Pluto for amusement) are wary of definitive statements.
Yeah Baby... (Score:1)
Yeah!
You, we go out on the town and swing, baby? Yeah!
Planet definition is bunk. (Score:3)
The whole problem with finding a definition of 'planet' is that stuff in the solar system can either be defined by its composition or its location. Objects with similar composition that look like exactly the same sort of thing when seen in isolation are often found in very different locations. And the IAU decided in its infinite wisdom to use location as the primary means classification rather than composition. Unfortunately, that decision is at odds with both sentimentality (as is seen with the whole Pluto fiasco) and with scientific usefulness. As we study extrasolar planetary systems, it has become clear that objects orbiting stars are very likely to change locations over time. Objects move from higher orbits to lower orbits and vice versa, Objects are captured into orbit by other objects, and objects are ejected from orbit around other objects, etc. So when studying a solar system, classifying objects by where they are in the system is scientifically meaningless as the objects quite possibly did not form in that location, and certainly may not remain in that location for the lifetime of the system's star.
So I propose Harperska's planetary classification system:
Terrestrial dwarf - large enough to attain hydrostatic equilibrium and differentiation. Mantle/crust comprised of rock, with iron core. 6 objects in solar system: Mercury, Venus, Earth, Luna, Mars, Vesta.
Asteroid - terrestrial dwarf like object, not large enough to attain hydrostatic equilibrium.
Ice dwarf - large enough to attain hydrostatic equilibrium and differentiation. Mantle/crust comprised of frozen volatiles (water, methane, ammonia), with rocky core. This class includes Ceres, the moons of the gas and ice giants, and Kuiper belt objects like Pluto and Eris.
Comet - ice dwarf like object, not large enough to attain hydrostatic equilibrium.
Gas Giant - comprised largely of hydrogen and helium. 2 objects in solar system: Jupiter and Saturn.
Ice Giant - comprised largely of volatiles (water, methane, ammonia) with a hydrogen/helium atmosphere. 2 objects in solar system: Neptune and Uranus.
Facebok's next new group (Score:1)