  We examine characteristics of circumbinary orbits in the context of current
planet formation scenarios. Analytical perturbation theory predicts the
existence of nested circumbinary orbits that are generalizations of circular
paths around a single star. These orbits have forced eccentric motion aligned
with the binary as well as higher frequency oscillations, yet they do not
cross, even in the presence of massive disks and perturbations from large
planets. For this reason, dissipative gas and planetesimals can settle onto
these "most circular" orbits, facilitating the growth of protoplanets. Outside
a region close to the binary where orbits are generally unstable, circumbinary
planets form in much the same way as their cousins around a single star. Here,
we review the theory and confirm its predictions with a suite of representative
simulations. We then consider the circumbinary planets discovered with NASA's
Kepler satellite. These Neptune- and Jupiter-size planets, or their
planetesimal precursors, may have migrated inward to reach their observed
orbits, since their current positions are outside of unstable zones caused by
overlapping resonances. In situ formation without migration seems less likely,
only because the surface density of the protoplanetary disks must be
implausibly high. Otherwise, the circumbinary environment is friendly to planet
formation, and we expect that many Earth-like "Tatooines" will join the growing
census of circumbinary planets.
