For planets in orbit around solar-like stars, 4 mas is needed to probe an adequate volume of one million cubic parsecs (0.5 AU orbits at 100 parsec distance). Large numbers of planets around low mass stars, with higher space densities, can be done at higher spatial resolution at shorter distances from Earth; the higher mass stars, with lower space density, would have to be done at greater distances to get a large sample (as for the AGNs). The filled aperture is needed because, once again, a systematic attack on the issue of spheres of influence is needed to encompass not particular, known cases of disks, jets and orbiting rocks, but all of the above in a fair sample of all stars.
