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