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Mystery of the hidden cosmos.
On 7/19/2015 5:47 PM, Gary Harnagel wrote:
On Saturday, July 18, 2015 at 11:37:18 PM UTC-6, Nicolaas Vroom wrote: Op donderdag 16 juli 2015 22:24:07 UTC+2 schreef Jos Bergervoet: On 7/16/2015 3:38 AM, Gary Harnagel wrote: Yes, there is a real deficit problem unless the microlensing technique can demonstrate that planet-sized objects are thicker than fleas on a dog (i.e., my extrapolation wildly underestimates the number of these bodies by several orders of magnitude). Do we actually have strong limits on the total mass of our own Oort cloud? Maybe there are more questions. The first question is slightly different: What is the shape of the Oort Cloud ? When you study the shape and size of Oort cloud in: https://en.wikipedia.org/wiki/Oort_cloud than you can see that its inner radius is small compared to its outer radius which is 10 times as large. The next question to answer is what is the mass of three times the inner radius multiplied by the average density of the Oort Cloud When this number is more or less the same you get an impression of how much baryonic matter there is in the Oort Cloud. Your link says the outer (spherical) Oort cloud has an estimated mass of about five earths. That statement is accompanied by "assuming that Halley's Comet is a suitable prototype for comets within the outer Oort cloud" And in the same paragraph concludes by saying that we nowadays have "lower estimates" than some time ago. So that's why I asked if we have any strong limits at all! ... It appears to me that even with there being more and more stuff at smaller and smaller diameters throughout interstellar space, their volumes (and therefore their masses) goes as 1/r^3, so the maximum mass fraction occurs at the red dwarf/brown dwarf level. Unless the numerical abundance goes up faster than 1/r^3 for even smaller r. So the question remains: how is all this restricted by experimental limits (from e.g. microlensing, or extinction effects anywhere in the EM or particle spectrum?) -- Jos [[Mod. note -- The typical comet in the outer Oort cloud has never (yet) had a close passage by the Sun. So Halley's Comet (which has had ~25 observed passages, and probably many more before the first recorded observations), is unlikely to be "typical". -- jt]] |
#12
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Mystery of the hidden cosmos.
Op zondag 19 juli 2015 17:47:09 UTC+2 schreef Gary Harnagel:
Your link says the outer (spherical) Oort cloud has an estimated mass of about five earths. One important document I have studied is document 3 which is mentioned often in https://en.wikipedia.org/wiki/Oort_cloud [[Mod. note -- I think the author is referring to Morbidelli, "Origin and Dynamical Evolution of Comets and their Reservoirs" http://arxiv.org/abs/astro-ph/0512256 -- jt]] My understanding was that the Oort Cloud contains the building blocks of the creation of the Sun and the planets. This process continues in the form of planets. At the same time these same building blocks can also form larger objects which stay inside the Oort Cloud. Document 3 gives a much more complex description in chapter 4. "Imagine an early time when the Oort cloud was still empty and the giant planets' neighborhoods were full of icy planetesimals." etc. A typical sentence in this document is at page 44: "This requires that Jupiter and Saturn were more effective in the real Oort cloud building process than in the simulations of [30]" The bottom part of page 44 is important starting with: "The way out" The document does not mention darkmatter. To include darkmatter in this document makes everything much more complex. Specific you have to mentioned how much dm there is in the Oort Cloud and almost everything related to Chapter 4. In theory there are Oort clouds around each star. Document 3 mentions that also. See for example page 30. The inter-Oort-cloud-space defines all space outside these Oort clouds The question is what are its constituents ie its composition. Its small objects are all invisible. Is that baryonic matter or are that Wimp's or wimpsicals? The third question is: Is there really an Oort Cloud around each star with empty space between the Oort Cloud of each star. It is easy possible that this huge region is not empty which can inhabitate a lot of mass. Your wiki link says the Oort cloud goes out two light years, which means that huge region is not empty, but it has been accounted for (apparently) in the five earth masses. The Oort cloud goes to 50000 AU in document 3, based on simulations. See page 31. I did not check the 2 ly. IMO what is outside this 50000 AU is not accounted for. Document 3 is highly based on simulations. In principle there is nothing wrong with this. These simulations for example can be very convincing if they show the right masses and distributions of our solar system but at the same time it does not mean that their predictions are correct towards on the mass and size of the Oort Cloud if not confirmed by observations. And this last part is very difficult. It appears to me that even with there being more and more stuff at smaller and smaller diameters throughout interstellar space, their volumes (and therefore their masses) goes as 1/r^3, so the maximum mass fraction occurs at the red dwarf/brown dwarf level. Not nearly enough to account for dark matter. Gary When you study the 1992 article you can see that the total number of Red and White dwarfs is much larger than the K dwarfs. For the amount of mass the same logic applies. My reasoning is that the R and W dwarfs are like the building blocks for the K dwarfs and the K dwarfs are the building blocks the G stars etc. What is missing are the building blocks of the R and W dwarfs. The 1992 article at the end reads: "For these reasons we know that the universe has more dark matter than luminous matter. But no one knows what dm is. It could be faint stars, like R and W dwarfs or it could be subatomic particles. Whatever it is dm may be the Grand Illusion in its most sinister incarnation: the universe is full of something that our instruments cannot see" The SA article writes: In addition to the normal "baryonic" matter in the cosmos, some hidden form of matter matter must be out there, gravitationally tugging on galaxies to keep them spinning as fast as they do and holding galaxies together. IMO let us first stictly investigate our own galaxy the Milky Way and come to an agreement what the solution of the dm issue is. This is already difficult enough. Do we need any dm? If so how much and where should it be? Inside the disc or outside the disc or both? If inside the disc where? etc Reading document 3 this whole picture becomes more complex. Nicolaas Vroom. |
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