The Size Distribution of Kuiper Belt Objects

We describe analytical and numerical collisional evolution calculations forthe size distribution of icy bodies in the Kuiper Belt. For a wide range ofbulk properties, initial masses, and orbital parameters, our results yieldpower-law cumulative size distributions, N_C propto r^{-q}, with q_L = 3.5 forlarge bodies with radii of 10-100 km, and q_s = 2.5-3 for small bodies withradii lesss than 0.1-1 km. The transition between the two power laws occurs ata break radius of 1-30 km. The break radius is more sensitive to the initialmass in the Kuiper Belt and the amount of stirring by Neptune than the bulkproperties of individual Kuiper Belt objects (KBOs). Comparisons withobservations indicate that most models can explain the observed sky surfacedensity of KBOs for red magnitudes, R = 22-27. For R < 22 and R > 28, the modelsurface density is sensitive to the amount of stirring by Neptune, suggestingthat the size distribution of icy planets in the outer solar system providesindependent constraints on the formation of Neptune.Comment: 24 pages of text, 12 figures; to appear in the Astronomical Journal, October 200