  Most young low-mass stars are born as binary systems, and circumstellar disks
have recently been observed around the individual components of proto-binary
systems (e.g. L1551-IRS5). Thus planets and planetary systems are likely to
form around the individual stellar components in sufficiently wide binary
systems. However, a good fraction of planets born in binary systems will in the
long run be subject to ejection due to gravitational perturbations. Therefore,
we expect that there should exist a free-floating population of Jupiter-like or
even Earth-like planets in interstellar space. There is hope to detect the
free-floating Jupiters through gravitational microlensing observations towards
the Galactic Bulge, especially with large-format detectors in the near-infrared
(e.g. with VISTA or NGST), on timescales of a few days.
