Kuiper-belt Binary Formation through Exchange Reactions

Astrophysics, abstract
astro-ph/0303113

From: “Y. Funato” <funato@chianti.c.u-tokyo.ac.jp>

Date: Wed, 5 Mar 2003 13:42:25 GMT   (149kb)

Authors:
Yoko Funato (Univ. of Tokyo),
Junichiro Makino (Univ. of Tokyo),
Piet Hut (Institute for Advanced Study),
Eiichiro Kokubo,
Daisuke Kinoshita (National Astronomical Observatory, Japan)

Comments: 10 pages, 3 Figures

Recent observationscite{Burnes2002,Veillet2002,Margot2002} have revealed an
unexpectedly high binary fraction among the Trans-Neptunian Objects (TNOs) that
populate the Kuiper Belt. While TNOs and asteroids are both thought to have
formed from the protoplanetary disk in similar ways, the observed TNO binaries
are strikingly different in four respectscite{Veillet2002}: their frequency is
an order of magnitude larger, the mass ratio of their components is much closer
to unity, and their orbits are much wider and more eccentric. Our solution to
this conundrum is to start with the formation of a TNO binary population that
is similar to the asteroid binary population, but that is subsequently modified
by three-body exchange reactions, a process that is far more efficient in the
Kuiper belt, because of the much smaller tidal perturbations by the Sun. These
exchange reactions naturally replace the initial companions by more massive
ones in a process that tends to lead to elongated orbits. Using detailed
three-body scattering experiments, we show that our mechanism can naturally
account for all four characteristics that distinguish TNO binaries from
main-belt asteroid binaries.

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