  Many planets are observed in stellar binary systems, and their frequency may
be comparable to that of planetary systems around single stars. Binary stellar
evolution in such systems influences the dynamical evolution of the resident
planets. Here we study the evolution of a single planet orbiting one star in an
evolving binary system. We find that stellar evolution can trigger dynamical
instabilities that drive planets into chaotic orbits. This instability leads to
planet-star collisions, exchange of the planet between the binary stars
("star-hoppers"), and ejection of the planet from the system. The means by
which planets can be recaptured is similar to the pull-down capture mechanism
for irregular solar system satellites. Because planets often suffer close
encounters with the primary on the asymptotic giant branch, captures during a
collision with the stellar envelope are also possible. Such capture could
populate the habitable zone around white dwarfs.
