Binaries in the Kuiper Belt

TL;DR

Binaries in the Kuiper Belt are numerous and provide vital insights into their formation, physical properties, and the evolution of transneptunian objects, making them key tools for understanding this distant region.

Contribution

This paper reviews the current knowledge of Kuiper Belt binaries, highlighting their significance in constraining formation models and their potential for future research.

Findings

48 binary systems are known in the Kuiper Belt.

Orbit measurements provide system masses and densities.

Binary properties support formation by dynamical capture.

Abstract

Binaries have played a crucial role many times in the history of modern astronomy and are doing so again in the rapidly evolving exploration of the Kuiper Belt. The large fraction of transneptunian objects that are binary or multiple, 48 such systems are now known, has been an unanticipated windfall. Separations and relative magnitudes measured in discovery images give important information on the statistical properties of the binary population that can be related to competing models of binary formation. Orbits, derived for 13 systems, provide a determination of the system mass. Masses can be used to derive densities and albedos when an independent size measurement is available. Angular momenta and relative sizes of the majority of binaries are consistent with formation by dynamical capture. The small satellites of the largest transneptunian objects, in contrast, are more likely formed from collisions. Correlations of the fraction of binaries with different dynamical populations or with other physical variables have the potential to constrain models of the origin and evolution of the transneptunian population as a whole. Other means of studying binaries have only begun to be exploited, including lightcurve, color, and spectral data. Because of the several channels for obtaining unique physical information, it is already clear that binaries will emerge as one of the most useful tools for unraveling the many complexities of transneptunian space.