On a Scattered-Disk Origin for the 2003 El61 Collisional Family - an Example of the Importance of Collisions on the Dynamics of Small Bodies

TL;DR

This paper proposes that the 2003 El61 collisional family originated from a collision between scattered disk objects, highlighting the significant role of collisions in shaping small body populations in the Kuiper belt.

Contribution

It introduces a novel hypothesis that the family resulted from scattered disk collisions, challenging previous assumptions about its formation in a primordial Kuiper belt.

Findings

Probability of collision in primordial Kuiper belt is less than 0.001.

Collision between scattered disk objects could have a 47% chance of producing such a family.

Collisions significantly influence the dynamical structure of small bodies in the Kuiper belt.

Abstract

The recent discovery of the 2003EL61 collisional family in the Kuiper belt (Brown et al., 2007) is surprising because the formation of such a family is a highly improbable event in today's belt. Assuming Brown et al.'s estimate of the size of progenitors, we find that the probability that a Kuiper belt object was involved in such a collision since primordial times is less than roughly 0.001. In addition, it is not possible for the collision to have occurred in a massive primordial Kuiper belt because the dynamical coherence of the family would not have survived whatever event produced the currently observed orbital excitation. Here we suggest that the family is the result of a collision between two scattered disk objects. We show that the probability that a collision occurred between two such objects with sizes similar to those advocated in Brown et al. (2007) and that the center of mass of the resulting family is on an orbit typical of the Kuiper belt can be as large as 47%. Given the large uncertainties involved in this estimate, this result is consistent with the existence of one such family. If true, this result has implications far beyond the origin of a single collisional family, because it shows that collisions played an important role in shaping the dynamical structure of the small body populations that we see today.