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New Papers On Planetary-Mass "Nomads" and Planetary Capture



 
 
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  #1  
Old February 20th 12, 11:01 AM posted to sci.astro.research
Robert L. Oldershaw
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Posts: 617
Default 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
  #2  
Old February 20th 12, 11:34 AM posted to sci.astro.research
eric gisse
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Posts: 303
Default New Papers On Planetary-Mass "Nomads" and Planetary Capture

"Robert L. Oldershaw" wrote in news:mt2.0-
:

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


Since you have often opined that the free floating planets are not only
_consistent_ with your numerology, but _predicted_ by them, could you
tell us when we can expect a published paper detailing how your
numerology predicts the free floating planets along with their
characteristics?
  #3  
Old February 23rd 12, 09:07 PM posted to sci.astro.research
Thomas[_6_]
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Posts: 1
Default 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  
Old February 24th 12, 09:40 AM posted to sci.astro.research
jacob navia[_5_]
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Posts: 543
Default 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
  #5  
Old February 24th 12, 09:43 AM posted to sci.astro.research
Robert L. Oldershaw
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Posts: 617
Default 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!"
  #6  
Old February 24th 12, 02:55 PM posted to sci.astro.research
eric gisse
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Posts: 303
Default 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!"

  #7  
Old February 25th 12, 07:19 PM posted to sci.astro.research
Thomas Smid
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Posts: 151
Default 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
  #8  
Old February 26th 12, 06:05 PM posted to sci.astro.research
jacob navia[_5_]
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Posts: 543
Default 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  
Old February 26th 12, 08:17 PM posted to sci.astro.research
Robert L. Oldershaw
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Posts: 617
Default 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  
Old February 26th 12, 09:29 PM posted to sci.astro.research
eric gisse
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Posts: 303
Default 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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