You're right, the galactic rotation does take that long, my apologies. My 25 million year figure refers to the Solar System's crossing the galactic plane, and is actually about 33 million years. Shoemaker suggested that the extinction-causing impacts on Earth came about as a direct or (more probably) indirect result of that oscillation.Rogue Planet Find Makes Astronomers Ponder TheoryEighteen rogue planets that seem to have broken all the rules about being born from a central, controlling sun may force a rethink about how planets form, astronomers said on Thursday... "The formation of young, free-floating, planetary-mass objects like these is difficult to explain by our current models of how planets form," Zapatero-Osorio said... They are not linked to one another in an orbit, but do move together as a cluster, she said... Many stars in our own galaxy, the Milky Way, may have formed in a similar manner to the Orion stars, she said. So there could be similar, hard-to-see planets floating around free near the Solar System.
by Maggie Fox
October 5, 2000
http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=2000Sci...290..103Z&db_key=AST
abstract: We present the discovery by optical and near-infrared imaging of an extremely red, low-luminosity population of isolated objects in the young, nearby stellar cluster around the multiple, massive star sigma Orionis. The proximity (352 parsecs), youth (1 million to 5 million years), and low internal extinction make this cluster an ideal site to explore the substellar domain from the hydrogen mass limit down to a few Jupiter masses. Optical and near-infrared low-resolution spectroscopy of three of these objects confirms the very cool spectral energy distribution (atmospheric effective temperatures of 1700 to 2200 kelvin) expected for cluster members with masses in the range 5 to 15 times that of Jupiter. Like the planets of the solar system, these objects are unable to sustain stable nuclear burning in their interiors, but in contrast they are not bound to stars. This new kind of isolated giant planet, which apparently forms on time scales of less than a few million years, offers a challenge to our understanding of the formation processes of planetary mass objects.
I do... but I do not believe the capture came from a free-roaming rogue, I think it is a planet from our own system (not necessarily a "Sol" based system) that we acquired during the break up of the Saturnian System which we were once part.
For a rogue to simply fall into an Earth orbit, it would have to be traveling at a much lower speed than the stellar speeds we were talking about. The current lunar velocity is about 15,500 MPH... far slower than the 490,000 MPH Galactic orbital speed...
By the way, our current understanding of the age of the Moon places it about 4 billion years old... makes for even less time for that wanderer to wander about the Galaxy.