Shaping the Kuiper belt size distribution by shattering large but strengthless bodies

Margaret Pan*, Re'em Sari

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

126 Scopus citations


The observed size distribution of Kuiper belt objects (KBOs) - small icy and rocky Solar System bodies orbiting beyond Neptune - is well described by a power law at large KBO sizes. However, recent work by Bernstein et al. (2004, Astron. J. 128, 1364-1390) indicates that the size distribution breaks and becomes shallower for KBOs smaller than about 70 km in size. Here we show that we expect such a break at KBO radius ∼ 40 km since destructive collisions are frequent for smaller KBOs. Specifically, we assume that KBOs are gravity-dominated bodies with negligible material strength. This gives a power-law slope q ≃ 3 where the number N>r of KBOs larger than a size r is given by N>r ∝ r1-q; the break location follows from this slope through a self-consistent calculation. The existence of this break, the break's location, and the power-law slope we expect below the break are consistent with the findings of Bernstein et al. (2004, Astron. J. 128, 1364-1390). The agreement with observations indicates that KBOs as small as ∼ 40 km are effectively strengthless.

Original languageAmerican English
Pages (from-to)342-348
Number of pages7
Issue number2
StatePublished - Feb 2005
Externally publishedYes

Bibliographical note

Funding Information:
We thank Oded Aharonson and Andrew MacFadyen for useful discussions. M.P. is supported by an NSF graduate research fellowship.


  • Impact processes
  • Kuiper belt objects


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