  In this paper we present results on the size distribution of circumstellar
disks in the Trapezium cluster as measured from HST/WFPC2 data. Direct diameter
measurements of a sample of 135 bright proplyds and 14 silhouettes disks
suggest that there is a single population of disks well characterized by a
power-law distribution with an exponent of -1.9 +- 0.3 between disk diameters
100-400 AU. For the stellar mass sampled (from late G to late M stars) we find
no obvious correlation between disk diameter and stellar mass. We also find
that there is no obvious correlation between disk diameter and the projected
distance to the ionizing Trapezium OB stars. We estimate that about 40% of the
disks in the Trapezium have radius larger than 50 AU. We suggest that the
origin of the Solar system's (Kuiper belt) outer edge is likely to be due to
the star formation environment and disk destruction processes
(photoevaporation, collisions) present in the stellar cluster on which the Sun
was probably formed. Finally, we identified a previously unknown proplyd and
named it 266-557, following convention.
