Capture of 20 km/s approach velocity interstellar comets by three-body interactions in the planetary system

Interstellar comets with velocities at infinity of 20 km s^-1 can be captured by three-body interactions within the planetary system. A semianalytic method is presented indicating that Jupiter is the only planet capable of scattering these comets into bound orbits. The time-averaged cross section for this process seems to be roughly five times the area of Jupiter. With an observational upper limit on interstellar comets of ≡10¹³pc^-3, the resulting capture rate amounts to only one comet every 60 Myr.