Radius of an object is shown assuming a moderate albedo of 0.15 for various heliocentric distances and apparent red magnitudes. The known objects in the Kuiper Belt region are complete to about 21st magnitude, shown by the shaded region below the dashed line. It is likely that everything under the dashed line at 21 mag is known. The radii used for the named objects in the figure are Pluto (1161 km), Mercury (2440 km), Mars (3396 km), Earth (6371 km), and an arbitrary lower limit on a hypothetical eccentric giant planet or companion to our Sun, sometimes called Nemesis or Tyche, with 10,000 km radius (Iorio 2009; Melott & Bambach 2010). In the distant solar system very large objects would easily be undetected to date.