Discussion in 'Astronomy, Exobiology, & Cosmology' started by Tortise, Mar 27, 2006.
Interesting. I will have to look into this more. It contradicts what I had heard in the past.
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"This enormous planet radiates twice as much heat as it absorbs from the Sun."http://www.enchantedlearning.com/subjects/astronomy/planets/jupiter/
This is really all you need to know to know that there is something wrong with the current model. Our current model does not include fisson of H or He which is what makes up almost all of jupiter.
This site says only 1.6 time - but still very significant. I think it is very unlikely that jupiter radiates all of that energy as a residual from compressing liquids? Doesn't sound very likely to me.
"Internal Source of Energy
Jupiter radiates 1.6 times a much energy as falls on it from the Sun. Thus, Jupiter has an internal heat source. It is thought that much of this heat is residual heat left over from the original collapse of the primordial nebula to form the Solar System, but some may come from slow contraction (liquids are highly incompressible, so Jupiter cannot be contracting very much.) This internal heat source is presumably responsible for driving the complex weather pattern in its atmosphere, unlike the Earth where the primary heat source driving the weather is the Sun.
The intense magnetic field of Jupiter is thought to result from electrical currents in this region of metallic hydrogen that is spinning rapidly and thought to compose 75% of the planet's mass. We are limited in our understanding of Jupiter's interior by the fact that we have no laboratory knowledge of the behavior of hydrogen under such conditions and are forced to rely on theory. Conversely, the properties of Jupiter provide a stringent test of our understanding of matter under such extreme conditions. "
One other possibility is that charged particles H+ and He+ are moving through jupiter emence magnetic field and this is energy is radiated away as heat. Could jupiter be using it's high rotational speed and it's emence magnetic field to create heat?
The topic of Earth's internal heat source was touched on in a an Earth Science thread. Page 6 of this thread has some excellent links posted by Ophiolite.
Thank you Laika that is very informative. But Jupiter is almost entirely H and He. You could make a very strong argument that the enormous amount of heat coming off of jupiter could not be because of compression either earlier in jupiter history or now, because you can't get that much heat from compressing fluids like H and He. Likewise you could argue that since jupiter is almost entirely H and He, that fission could not possibly explain the excess energy. Following this logic, jupiter would put out the least amount of heat of all the planets, insted it puts out the most. To me it's obvious that we don't have the whole story on this excess energy, and there are only 2 or 3 other things that could explain it.
I'm not sure. As Hipparchia said, Jupiter probably has a significant core of iron and rock, so I'd expect radioactive decay to contribute a little. I'm more a geologist than a physicist, so I can't really comment on the feasibility helium condensation and gravitational contraction as heat sources. My hunch would be that they all play a role, and that fusion is unnecessary.
But as I say, I wouldn't know what to do with the numbers even if I had them.
Jupiter has a core of about 10 earths or so - this comprises only about one tenth of one percent of jupiter's mass.
Mass (1024 kg) ---- --- ----- 1,898.6---- 5.9736 ---- ----317.83
Volume (1010 km3)-- ------- 143,128 ---- 108.321----- -1321.33
Radius (1 bar level) (km)--
Equatorial -------------- ----- 71,492---- 6,378.1 ------ 11.209
Volumetric mean radius (km) --- 69,911---- 6,371.0 ---- 10.973
Mean density (kg/m3) ----------- 1,326---- 5,515 ---- -----0.240
As you can see, jupiter is more then 1300 x the volume of earth, and only .24 x the density. This means that it is obvious that it has a small core relative to it's very large size.
C'mon you guys grow a pair. Can't you see there is something wrong here - something we don't yet understand?
There's undeniably a lot to do with it that I don't understand. I don't see why the fact that Jupiter has a relatively small rocky/metallic core necessitates fusion as an additional heat source. As I said, I would expect radioactive decay to make some contribution to the planet's internal heat - if the composition of its core is similar to that of the whole Earth, why wouldn't it? I don't think anyone in this thread has claimed that radioactive decay accounts for all or even most of the heat though.
Your claim that those processes put forward already are insufficient to explain Jupiter's heat output seems like a hunch at the moment. Do you have any maths that can back you up? You expect Jupiter's continued gravitational contraction to yield the least energy of all the planets because of its hydrogen and helium composition, but are you forgetting that it is also the most massive and has the strongest gravitational field?
Much like how a refrigerator or a air conditioner works (it compresses gas on the outside and releases compressed gas enclosed on the inside to cool) once something has compressed, it doesn't continue to produce heat - otherwise a balloon would continue to radiate heat as long as it was inflated. The law of incompressible fluids makes the thought of heat from gravitational compression very very unlikely. About the rocky core - I could do the math, but to me it is really self evident that a small rocky core comprising only one tenth of one percent of the planet could radiate that much heat. I'll consider doing the math tomorrow, but it is really self evident. Why do you think that asteroids in space with heavy metals aren't hot like the inside of planets? Surely they have decaying material also? If I did the math would it convince anyone? For Pete's sake jupiter puts out more extra energy then the earth does per sq. meter. How much math could be more convincing then that - when the earth is all terrestrial and jupiter is 1/1000 th terrestrial?
"Jupiter probably has a core of rocky material amounting to something like 10 to 15 Earth-masses."http://www.nineplanets.org/jupiter.html
I see where you're coming from now. I don't think that the continued gravitational contraction of Jupiter relates to gas laws and compression though. Rather, it involves the conversion of gravitational potential energy (inherent in the spatial relationship between the mass of the material and the centre of mass of the system) into heat energy. At least that's my understanding of it.
As for the asteroids, as has already been discussed (and is still a source of debate regarding the Earth's heat source), the unstable elements such as uranium and potassium are generally not chemically compatible with iron - they are not siderophile elements. This leads me to imagine that they might not be present in large quantities in such bodies. Even if they were relatively concentrated, perhaps the smaller volume to surface ratio might affect how much radiation was emitted per unit area.
Like I said (and I may be wrong) but once something is compressed it doesn't continue to produce heat - think of the bottom of the ocean, the emence pressure at 3 miles down and how cold it is. Fluids don't compress, and much heating is from heavier elements moving down past lighter elements - something you wouldn't have at this point in jupiter.
I just found this on NASA's web site:
"Jupiter emits twice as much heat as it absorbs from the Sun, which indicates it has its own internal heat source. Astronomers estimate the core temperature at 20,000 degrees Celsius, approximately three times greater than the temperature of the Earth's core. "http://starchild.gsfc.nasa.gov/docs/StarChild/solar_system_level2/jupiter.html
A quite different view of the role of uranium in the Earth is the theory that much of the uranium in the primordial planet sunk to the core and has formed a core there, some 8 km across, which has been fissioning ever since. The depletion of U-235 over geological time has not terminated the reaction because this core is a fast reactor (not requiring any moderator) which breeds plutonium-239 from the U-238. The georeactor theory has relatively little supporting evidence, and is not widely supported."
what's so weird if jupiter gives off some heat? even our solid earth has a liquid and hot nucleus which gives off some heat.
Read the thread, it's not even two full pages.
ok, i read it. but i often don't agree with modern physics.
in my physics planets are magnets and they rotate because of magnetism and rotation causes heat.
the inside, the nucleus, of planets rotate faster than the core, and the variation of speed in different layers of planets cause heat.
jupiter is a planet like the earth, and the sun is also just a big rock!! but because it's the center, and because it's so big, its core can't rotate as fast enough so it becomes warm and liquid.
you're also happy like the sun when people dance around you, right? yep, that's why the sun shines, it's happy.
Ya 20,000 degrees centigrade - Tell me, if there is so much friction because the core doesn't rotate as fast, why doesn't the core speed up and rotate at the same rate? Some magical force? This is real physics c7ityi with real cause and effect. It is (yes I'll say it) impossible that friction is causing that heat. Not the least of which because we would be able measure jupiter slowing down. Instead, jupiter is rotating very very fast. You don't get something for nothing.
20000 degree Celsius = 36032 degree Fahrenheit - do you know how much energy that is?
At the surface of jupiter the pressure is 1000 bars. Jupiter gets hotter the at the pressure increases - much like on the earth how it is very cold at the tops of mountains - because there is more oppertunity for an object to heat up. Imagine you're in space approaching a hot planet - when you enter the thin part of the atmosphere, a few atoms transfer some of their energy - but is not enough to heat up much because of the coldness of space. This has more to do with the frequency of interaction and shouldn't be confused with pressure in fluids or solids. If pressure was a constant source of heat, then oxygen and compressed air tanks would always be hot. When they are filled, they get hot - like a bicycle tire does. But then the heat dissipates.
"The temperature reaches 70 degrees F (21 degrees C) -- "room temperature" -- at a level where the atmospheric pressure is about 10 times as great as it is on Earth." http://www.worldbook.com/wc/popup?path=features/jupiter&page=html/intro.htm&direct=yes
Near the planet's center, the temperature is much higher. The core temperature may be about 43,000 degrees F (24,000 degrees C) -- hotter than the surface of the sun.
Solar irradiance (W/m2) 50.50
http://nssdc.gsf...ould be due to decay or to heat of formation?
I love this quote. But, unfortunately, we're all constrained by the same set of laws. They're not an opt-in/opt-out kind of thing.
Firstly, the idea is that it is still compressing - gravitational contraction. A slow process that does generate heat. This is not disputed by astronomers. What is in question is whether this is sufficient to generate the heat that is observed.
Secondly, leading on from that, you seem to be viewing this as a great mystery. The problem is simple: we do not know the detailed internal structure of Jupiter. Consequently there are a number of plausible explanations for the extra heat. Astronomers have no doubt that one or more of these will turn out to be the correct one, but without the more accurate model of Jupiter's interior they have no way of choosing between the various options.
Thirdly, of course you can compress fluids. (For one thing gas is a fluid. )Liquids are less compressible than gases, but I assure you they can be compressed.
You could certainly be right. And you certainly represent the consensus.
You heard it here first ladies and gentlemen! Jupiter is shrinking and this is what is powering it. So get a good look while you still can! Forget that we can detect the most minute change - forget minute of arc. The best minds in astronomy have spoken. Gosh, I hope it can still go on compressing forever so we won't lose the jupiter that we know and love! Simply amazing that the most observed planet of all time has been shrinking right before our eyes and we didn't even notice it. Well mystery solved.
76,485,181,679 Watts x (1 millennium = 31,536,000,000 seconds) = 2412.e18
x (4 billion years / 1000) = 9.648e+27 wattsecond = 9.648e+21 megajoule
(very conservative estimate)
I don't know if that makes sense? That means that the water in the bottom of the ocean can still be compressing and producing heat right? Have you ever heard of the thermal haline conveyer? It wouldn't work if you were right in the very slightest. Fluids don't give off much heat under compression, and when they do it's only once. One degree would stop this conveyer. Look at the dynamics of the gravitational fields: Earth's is much more focused. Jupiter's density is about .24 of what the earth's is.
What would make anyone think that it would be a dynamic process? Does it make sense that water at the bottom of the ocean was compressing more and more for billions of years? This is an impossible argument. Liquid doesn't keep compressing any more then gas would at a certain pressure. The diffuse gravitational attraction that jupiter has is not likely to increase in intensity much is it? I mean think about it. Look at the density that it is now - not much different then a much smaller object composed of the same thing.
Here are some of the properties of the superfluid helium II.
-It carries no thermal energy (no entropy): all of the heat energy is in the normal component http://18.104.22.168/search?q=cache...m.html liquid Helium&hl=en&gl=us&ct=clnk&cd=1
Mean density (kg/m3) Jupiter 1,326 Earth 5,515 Ratio0.240 (that is Earth is more than 4x more dense)
Gravity (eq., 1 bar) (m/s2) 24.79 9.80 2.530
Jupiter gravitation intensity is 2.53 times what earth's is at best - it gets much closer the further down you get because the earth is much more dense.
I will give you one thing: Helium is highly compressable as a liquid. "Helium solidifies only under great pressure. The resulting colorless almost invisible solid is highly compressible; applying pressure in the laboratory can decrease its volume by more than 30%. With a bulk modulus on the order of 5×107 Pa  it is 50 times more compressible than water. Unlike any other element, helium will fail to solidify and remain a liquid down to absolute zero at normal pressures. Solid helium requires a temperature of 1–1.5 K and about 26 standard atmospheres (2.6 MPa) of pressure. It is often hard to distinguish solid from liquid helium since the refractive index of the two phases are nearly the same. The solid has a sharp melting point and has a crystalline structure." But He is only one part in ten in Jupiter.
Density, Liquid @ B.P., 1 atm: 7.798 lb./cu.ft.
If you look at the density, your theory doesn't make much sense does it? It's not any more dense then you would expect it to be with about 10% He and about 90% H - then liquid H and He on earth. Hmmmmmmm
And if you figure the other elements known to exist in the atmosphere, and the rocky core, the argument just gets worse and worse for those of us who care to consider the facts. Doesn't it make sense that if jupiter were compressing, that it would get more dense? Hello......
"Liquid hydrogen has a density of 0.07 grams per cubic centimeter, whereas water has a density of 1.0 g/cc" http://www-formal.stanford.edu/jmc/progress/hydrogen.html
3He 0.000137%* He is stable with 1 neutrons
4He 99.999863%* He is stable with 2 neutrons (so most He is 4He)
The point is something can only be compressed once for heat. After that heat has dissipated the resulting compression does not continue to produce heat. The majority of the planet is liquid, and therefore very unlikely to put out much heat from compression. Liquids are far far less compressible then gasses. If you really entertain the concept that jupiter is still compressing and that is what gives off so much heat then that's your mistake. I just think it should be obvious to people like you, that the concept doesn't make much sense. It doesn't take much thinking to realize that due to the density, the gravity isn't much stronger then the Earth's (intensity) under the surface, and furthermore, it's much more diffuse in jupiter then Earth's - different dynamics in the core. I mean do the math - compression only counts once - if it expands again it cools by the same mechanism. So if it expands and contracts again, sum = 0 energy in the form of heat. I guessed I'm encouraged by your statements because in my mind your logic doesn't hold up, therefore it is a mystery - at least to some people anyway.
If what you said were true that would mean that it was slowly contracting over billions of years , and still putting out that tremndous amound of heat - Fluids. And according to the theory that compression of H and He is responciple, must be at the lowest level of thermal energy it has ever been. I think that's rather naive.
Like I said though, you're entitled to your own opinion, and it could be the correct one. But at the moment it doesn't make much sense to me.
I'll offer more info tomorrow to bolster my case. Some of it will be trying to find out exactly how much heat can be gotten out of H and He when it is compressed. I'm sure that it is nowhere near the emmence amount of heat that jupiter has put out. Off hand one of the pertainent equations is Q=c x m x change in T for specific heat. Phase change should also be figured in I suppose.
Wrong. The Earth's oceans, are not Jupiter. The scale and composition change the game. You seem to wish to question, even discard concepts, simply because you do not understand them. Is that wise? Is it the route to wisdom?
It's not my theory. I do not know of any scientist who disputes that this mechanism will contribute some of the excess heat. Do you?
Then it is a mistake I share with many knowledgeable astronomers and physicists.
I'm sensing a lot of hostility here, and I don't understand why. Yes, I have challenged your belief that there is something mysterious about Jupiter's heat production. I have asserted the mechanism is not mysterious, merely unknown in detail: there are options.
So, what exactly is a person like me, and why should your viewpoint be obvious to me?
You do the math and demonstrate that the consensus, majority view is flawed.
It isn't a tremendous amount of heat. You seem to be imagining the heat output that would be necessary if Jupiter were outputting twice as much as it receives and were orbiting at 1 AU. It isn't.
A naivety I am happy to share with people who hold doctorates in astrophysics.
And to repeat. It isn't my opinion, it is a generally accepted fact. Fortunately facts are not dependant upon our ability, or inability, to comprehend them.
Well how can I possibly argue with someone so much smarter then myself?
Ya! I give up! you're right! Jupiter is shrinking! You've converted me! The best minds have spoken
God knows we have never been wrong about the universe - oh wait maybe just about every time we make a theory.....Hmmmm but we are much smarter now and are never wrong... Wait ....well I'll get back to you on that..God knows history will look back on us and say: "they had everything right! - those guys back in 2006 really had their stuff together! They even knew that jupiter was shrinking! - Those guys were so so smart"
Forget that the numbers just don't add up. It's just nicer to believe that jupiter is shrinking! How fun is this? Please Register or Log in to view the hidden image!
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I am not trying to give offense Tortise, thought that seems to be what has happened. Your last response, or more precisely retort, is quite dismissive and insulting in its sarcasm. That is slightly wounding, since I really don't think I have written anything to merit that kind of response.
I have expressed a contrary view, true. I have pointed out, because it is so, that science has several perfectly satisfactory explanations for Jupiter's heat - it just has not yet decided which is the most important. My position is based on accepted science. Your position seems to based upon the fact that you do not think the conventional explanations are likely, yet you offer no evidence to dismiss these.
Now, because I keep pointing out the flaw in that position - surely you see it is unscientific - you respond with such sarcasm. Was that really necessary?
I have just seen your edit, where you add a second paragraph. Now I think you are just being silly.
Of course science does not have all the answers. But your entire objection to the generation of heat through gravitational collapse is that you do not think it is very likely. Come on! We should discard solid science because Tortise doesn't understand it. That's stupid.
Offer one piece of evidence for why established science is wrong, but don't keep offering up opinion based on ignorance.
See, now you've made me angry. Excuse me.
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