On May 19, 8:56*am, wrote:
"A team of astronomers has identified a novel
new kind of galactic wanderer - lone, Jupiter-sized
planets expelled from forming solar systems
and drifting in the empty void between the stars.

The researchers, led by Takahiro Sumi of Japan's
Osaka University, spotted 10 such free-floating
"orphan planets" in data from a 2006-7
microlensing survey of our galaxy's centre, which
searched for the tell-tale sign of transiting bodies'
gravitational fields distorting light from distant
stars.

Team member David Bennett, of the University of
Notre Dame in Indiana, explained that this first
sighting in a small portion of the Milky Way
points to enormous numbers of orphans. He
said: "Our survey is like a population census.
We sampled a portion of the galaxy, and based
on these data, can estimate overall numbers in
the galaxy.""

See:

http://www.theregister.co.uk/2011/05/19/orphan_planets/

This is exactly what I've been saying all along.
http://www.nature.com/news/2011/1105....2011.303.html
http://www.jpl.nasa.gov/news/news.cfm?release=2011-147

Rogue planets and their moons simply have to exist in great numbers
by now.

As main-sequence stars consume their fuel and unavoidably blow off
considerable mass as they eventually turn themselves into white dwarfs
or neutron stars, whereas there's simply no way they can possibly hold
onto their planets when having a final mass reduction of at least 4:1
and in some cases near 8:1. It seems even once near 75% of their
progenitor mass isn’t going to be holding onto whatever planets unless
the orbital velocity of such planets slows way down.

Other nearby or passing stars and especially any rogue neutron stars
could also help pull planets away from their parent star. Otherwise
the only dynamic tidal holding method of planets sticking with their
parent star as it shrivels into a white dwarf is for them planets to
lose orbital velocity, and that’s not likely to happen.

Our sun is supposedly a third generation star, so there's many planets
from the first two stellar generations that are still out there doing
their rogue interstellar thing. One of those could be Tyche or
possibly any one of the Sirius(B) planets might not be too far away,
especially nearby as the Sirius Oort cloud is closing in on our Oort
cloud, whereas there’s no telling what could show up as seemingly out
of nowhere.

Some of the surviving gas giants or otherwise extremely icy rock
planets could have earth sized moons and even a few offering
Goldilocks survival potential, but no doubt they’d be cold and cranky
as hell unless they had tunneled deep into the ground for their
geothermal energy.

With a potential 1e12 rogue planets and their moons (some of those
Earth sized) to pick from, with our spendy JWST it shouldn't be all
that hard to locate a few within our galactic neck of the woods, and
keep track of their migrations (possibly even estimate where they
originated from).

Our moon could have easily been worth more than 8e22 kg as an icy
rogue intruder. Such and icy rogue planetoid would actually make for
a very good multigenerational spacecraft that offers terrific
interstellar capability. Otherwise, sorry about my being right again.

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Brad Guth, Brad_Guth, Brad.Guth, BradGuth, BG / “Guth Usenet”