Reduced Hill radii of 580 known inner exoplanets versus their radii in units of Jupiter’s radius. Dashed horizontal lines mark the lower boundaries of plot areas where these exoplanets can in principle have moons with the smallest masses as labelled in the graph. For each specific |exoplanet shown with a dot in this plot, the mass of a survivable moon should be above the dashed line (above the upper line, for putative moons of M_m = 0.01 M_p, or above the lower line, for putative moons of M_m = 0.05 M_p).