Triplanetary

Two thousand million or so years ago two galaxies were colliding; or, rather, were passing through each other. A couple of hundreds of millions of years either way do not matter, since at least that much time was required for the inter-passage. At about that same time—within the same plus-or-minus ten percent margin of error, it is believed—practically all of the suns of both those galaxies became possessed of planets.
There is much evidence to support the belief that it was not merely a coi...