  Planetesimal formation is a common by-product of the star formation process.
Taking the dynamical history of the Solar system as a guideline -- in which the
planetesimal belts were heavily depleted due to graviational perburbation with
the giant planets -- and assuming similar processes have take place in other
planetary systems, one would expect the interestellar space to be filled with
extra-solar planetesimals. However, not a single one of these objects has been
detected so far entering the Solar system, even though it would clearly be
distinguishable from a Solar system comet due to its highly hyperbolic orbit.
The Large Synoptic Survey Telescope (LSST) will provide wide coverage maps of
the sky to a very high sensitivity, ideal to detect moving objects like comets,
both active and inactive. In anticipation of these observations, we estimate
how many inactive "interstellar comets" might be detected during the duration
of the survey. The calculation takes into account estimates (from observations
and models) of the number density of stars, the amount of solids available to
form planetesimals, the frequency of planet and planetesimal formation, the
efficiency of planetesimal ejection, and the possible size distribution of
these small bodies.
