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New Papers On Planetary-Mass "Nomads" and Planetary Capture
Those following the exciting developments relating to the apparent
discovery of trillions of unbound, planetary-mass "nomads", and the growing interest in the planetary-capture hypothesis, will surely want to take a look at the following papers posted to arxiv.org recently. http://arxiv.org/abs/1201.2175 "Planet-planet scattering alone cannot explain the free-floating planet population" http://arxiv.org/abs/1201.6582 "Exoplanets Bouncing Between Binary Stars" http://arxiv.org/abs/1202.2362 "On the origin of planets at very wide orbits from re-capture of free floating planets" RLO Discrete Scale Relativity http://www3.amherst.edu/~rloldershaw |
#3
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New Papers On Planetary-Mass "Nomads" and Planetary Capture
On Feb 20, 10:01*am, "Robert L. Oldershaw"
wrote: Those following the exciting developments relating to the apparent discovery of trillions of unbound, planetary-mass "nomads", and the growing interest in the planetary-capture hypothesis, will surely want to take a look at the following papers posted to arxiv.org recently. http://arxiv.org/abs/1201.2175*"Planet-planet scattering alone cannot explain the free-floating planet population" http://arxiv.org/abs/1201.6582*"Exoplanets Bouncing Between Binary Stars" http://arxiv.org/abs/1202.2362*"On the origin of planets at very wide orbits from re-capture of free floating planets" RLO Discrete Scale Relativityhttp://www3.amherst.edu/~rloldershaw A simple order of magnitude calculation shows that even with a free floating planet density twice the stellar density (as suggested by the references you quoted), the chance of a star capturing a planet in its lifetime is practically zero: density of free floating planets N = 2/pc^3 velocity of free floating planets v = 30 km/sec = 10^-12 pc/sec solar system capture cross section Q = pi*(1 AU)^2 = pi*(5*10^-6 pc)^2 = 8*10^-11 pc^2 This means that statistically, the average time for the sun to capture a floating object within a distance of 1 AU is T= 1/(N*Q*v) = 1/(2 *8*10^-11 * 10^-12 ) sec = 6*10^21 sec = 1.9*10^14 years. This is almost 100,000 times longer than the age of the sun, so the chance for the sun having captured a free floating object to date is practically zero. Thomas |
#4
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New Papers On Planetary-Mass "Nomads" and Planetary Capture
Le 23/02/12 21:07, Thomas a écrit :
A simple order of magnitude calculation shows that even with a free floating planet density twice the stellar density (as suggested by the references you quoted), the chance of a star capturing a planet in its lifetime is practically zero: density of free floating planets N = 2/pc^3 velocity of free floating planets v = 30 km/sec = 10^-12 pc/sec solar system capture cross section Q = pi*(1 AU)^2 = pi*(5*10^-6 pc)^2 = 8*10^-11 pc^2 This means that statistically, the average time for the sun to capture a floating object within a distance of 1 AU is T= 1/(N*Q*v) = 1/(2 *8*10^-11 * 10^-12 ) sec = 6*10^21 sec = 1.9*10^14 years. This is almost 100,000 times longer than the age of the sun, so the chance for the sun having captured a free floating object to date is practically zero. Thomas AT ONE Astronomical unit. Sedna is at 1000 AU, what squared gives a factor of 1 million in your formula: pi*(AU)^2 That makes 1.9*10^8 years, i.e. 190 million years, nothing at astronomical scales. I wonder then if Sedna is not a captured free floating planet that happened to pass nearby. Interesting... jacob |
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New Papers On Planetary-Mass "Nomads" and Planetary Capture
On Feb 23, 3:07*pm, Thomas wrote:
A simple order of magnitude calculation shows that even with a free floating planet density twice the stellar density (as suggested by the references you quoted), the chance of a star capturing a planet in its lifetime is practically zero: -------------------------------------------------------------------------------------- One of the papers determines the probability of "nomad" capture by a star would be in the 3% to 5% range. The paper notes that 3-5% is not a high probability, but in the relevant star clusters, typically containing on the order of 1,000 stars, this represents a significant number of captured planets. Any mathematical calculation used to approximate what actually happens in nature is only as good as the assumptions it starts with. If one or more critical assumptions is wrong, then the mathematical results can seriously mislead and give wrong "answers". I previously gave a simple and very strong observational argument for the possibility that planet capture was reasonably common, but the post was rejected as "too speculative" since it involved an analogy to atomic scale systems. [Mod. note:... which meant it was not either a strong or an observational argument. -- mjh] I think we are going to have to modify many of our set-in-stone assumptions regarding stellar and exoplanet systems. Observations have and will continue to demand it. RLO http://www3.amherst.edu/~rloldershaw Discrete Scale Relativity Faster-than-light neutrinos? "In a pig's eye!" |
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New Papers On Planetary-Mass "Nomads" and Planetary Capture
"Robert L. Oldershaw" wrote in
: On Feb 23, 3:07*pm, Thomas wrote: A simple order of magnitude calculation shows that even with a free floating planet density twice the stellar density (as suggested by the references you quoted), the chance of a star capturing a planet in its lifetime is practically zero: ----------------------------------------------------------------------- --------------- One of the papers determines the probability of "nomad" capture by a star would be in the 3% to 5% range. The paper notes that 3-5% is not a high probability, but in the relevant star clusters, typically containing on the order of 1,000 stars, this represents a significant number of captured planets. You do realize that star clusters are different from the galactic stellear neighborhood at large, right? I assume you noticed the predicted orbits of the captured bodies to be between 100 and 10^6 AU, the latter case being a severe test of the definition of "capture". So even if you could generalize this result out (you can't, the galaxy is not a cluster) it would still mean just north of nothing for observation at this time because none of our exoplanet detection techniques are sensitive to objects at that range. Any mathematical calculation used to approximate what actually happens in nature is only as good as the assumptions it starts with. If one or more critical assumptions is wrong, then the mathematical results can seriously mislead and give wrong "answers". I previously gave a simple and very strong observational argument for the possibility that planet capture was reasonably common, but the post was rejected as "too speculative" since it involved an analogy to atomic scale systems. Perhaps it had no actual calculations or observations supporting it, much like the last several times you brought it up? You will get zero traction arguing "but the systems are similar!" because your numerology has failed every observational test thus far. [Mod. note:... which meant it was not either a strong or an observational argument. -- mjh] I think we are going to have to modify many of our set-in-stone assumptions regarding stellar and exoplanet systems. Observations have and will continue to demand it. Sure, our understanding of exoplanets has been and is continuing to grow and those assumptions are being challenged all the time. However nobody is going to take your numerology seriously because you have a very long history of not concerning yourself with its' fatal flaws. I note you have given up entirely on discussing them with me, as snipping everything and saying 'woofy' won't fly here. If you want people to take you seriously, try making a quantitative prediction. You say your numerology predicted those free floating planets....lets see the calculation. Let's see some numbers. Until you have that, you are just another USENET poster with a theory. RLO http://www3.amherst.edu/~rloldershaw Discrete Scale Relativity Faster-than-light neutrinos? "In a pig's eye!" |
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New Papers On Planetary-Mass "Nomads" and Planetary Capture
On Feb 24, 8:40*am, jacob navia wrote:
[Mod. note: quoted text trimmed -- mjh] Sedna is at 1000 AU, what squared gives a factor of 1 million in your formula: pi*(AU)^2 That makes 1.9*10^8 years, i.e. 190 million years, nothing at astronomical scales. I wonder then if Sedna is not a captured free floating planet that happened to pass nearby. Interesting... At 1000 AU, the orbital speed is of the order of 1 km/sec, and this is about the speed an object must have for there to be any chance of being captured. So 30 km/sec (which is what I assumed above for the average peculiar speed of interstellar objects) is much too high for a capture. And the density of objects with a speed of just 1 km (or less) would be much smaller. If you assume a Maxwell-Boltzmann distribution, then the density of particles is proportional to v^2 for speeds small compared to the average speed, so in this case only (1/30)^2 = 1/900 of the total density N. And because v would be smaller by factor 1/30 as well, you would then still be at a time of 5*10^12 years, i.e. there would be just a 1/1000 chance that it has occurred during the lifetime of the sun. And this is only the probability for an object to get sufficiently close to the sun in the first place. You then have to multiply this with the (conceivably even much smaller) probability that it has a very close encounter with an object of a comparable size in the solar system (because that is the only way for it to lose kinetic energy and thus become captured by the solar system). But anyway, as we know from previous discussions, Robert suggests the capture theory as a general alternative to explain the formation of planetary systems, so also at 1AU or even closer (because that is what his principle of a fundamental similarity between planetary systems and atomic systems would demand). Thomas |
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New Papers On Planetary-Mass "Nomads" and Planetary Capture
Le 25/02/12 19:19, Thomas Smid a écrit :
At 1000 AU, the orbital speed is of the order of 1 km/sec, and this is about the speed an object must have for there to be any chance of being captured. So 30 km/sec (which is what I assumed above for the average peculiar speed of interstellar objects) is much too high for a capture. And the density of objects with a speed of just 1 km (or less) would be much smaller. If you assume a Maxwell-Boltzmann distribution, then the density of particles is proportional to v^2 for speeds small compared to the average speed, so in this case only (1/30)^2 = 1/900 of the total density N. And because v would be smaller by factor 1/30 as well, you would then still be at a time of 5*10^12 years, i.e. there would be just a 1/1000 chance that it has occurred during the lifetime of the sun. And this is only the probability for an object to get sufficiently close to the sun in the first place. You then have to multiply this with the (conceivably even much smaller) probability that it has a very close encounter with an object of a comparable size in the solar system (because that is the only way for it to lose kinetic energy and thus become captured by the solar system). The key parameter here is the density of the free floating planets. A press release published yesterday by Stanford University says that there should be 100 000 (one hundred thousand) planets for each star. Please look in this URL, I may have misunderstood something: http://groups.google.com/group/sci.s...0725bb1d?pli=1 That is a 5 orders of magnitude more than what you assumed in your calculations. The problem with astronomy now is that the fact that we have entered space and we have now space telescopes opens such an avalanche of new data that many theories just will not stand the test of time. But anyway, as we know from previous discussions, Robert suggests the capture theory as a general alternative to explain the formation of planetary systems, so also at 1AU or even closer (because that is what his principle of a fundamental similarity between planetary systems and atomic systems would demand). I wasn't arguing either for or against Robert's theory. The fact that so many free floating planets are there is just mind boogling. That has surely consequences but I am not competent to figure them out. jacob |
#9
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New Papers On Planetary-Mass "Nomads" and Planetary Capture
On Feb 25, 1:19*pm, Thomas Smid wrote:
But anyway, as we know from previous discussions, Robert suggests the capture theory as a general alternative to explain the formation of planetary systems, so also at 1AU or even closer (because that is what his principle of a fundamental similarity between planetary systems and atomic systems would demand). ---------------------------------------------------------------------------- A man of remarkable insight into natural philosophy, whom I will not name lest I be accused of comparing myself to him, once said words to the effect that: 'often in science, progress has been made by considering analogies between things that were previously thought to be unrelated'. With this perceptive comment in mind, I would urge readers to consider what the physics of atomic scale plasmas might suggest in terms of the formation of multiple stellar systems like exoplanet systems. Consider a plasma of nuclei, electrons and excited atoms, i.e., not a fully ionized plasma, but one that allows the capture of electrons by the nuclei, and subsequent ejection. In such a plasma you get an extremely rich physics that includes a very large number of possible "species", configurations, energy states, ellipticities, discreteness, quasi-continuous evolution for the highest energy states, etc. Were we to give some credence to the possibility that atomic scale plasma behavior might provide useful analogies for guiding our thinking about stellar scale "formation" behavior, it is possible that new and useful insights would emerge. For example, if we wondered whether capture into low-n orbit or capture into a high-n orbit were more likely, we could use what is well-known to occur on the atomic scale as a guide to what we might expect for stellar scale systems. Capture into high-n states is far more likely. Most of the low-n systems form from the relatively slow relaxation of high-n systems, not direct capture to low-n states. Using such an analogy as a mere heuristic guide, or using it as a more formal theoretical assumption, is a free choice. Eventually the empirical match between analogy and reality determines the true status of the analogy. Best, RLO http://www3.amherst.edu/~rloldershaw Discrete Scale relativity |
#10
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New Papers On Planetary-Mass "Nomads" and Planetary Capture
"Robert L. Oldershaw" wrote in
: [...] For example, if we wondered whether capture into low-n orbit or capture into a high-n orbit were more likely, we could use what is well-known to occur on the atomic scale as a guide to what we might expect for stellar scale systems. Capture into high-n states is far more likely. Most of the low-n systems form from the relatively slow relaxation of high-n systems, not direct capture to low-n states. Since we haven't seen any evidence that capture is an even slightly relevant behavior for planetary systems, I'm not sure where you are going for this. Besides, there's literally no analogy between atomic state transitions and planetary orbits. Using such an analogy as a mere heuristic guide, or using it as a more formal theoretical assumption, is a free choice. Eventually the empirical match between analogy and reality determines the true status of the analogy. How is there any analogy at all when the dynamical equations of the system are not anywhere near similar? Schroedinger vs Newton, etc. It seems more like any commonalities between the two are due to mathematical similarities in the system solutions, eg with traits similar to bound orbits and whatnot. How many times does the analogy have to fail before you sit down and admit to yourself *it does not work* ? Best, RLO http://www3.amherst.edu/~rloldershaw Discrete Scale relativity |
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