The Orbital and Spatial Distribution of the Kuiper Belt

Abstract

Models of the evolution of Neptune's migration and the dynamical processes at work during the formation of the outer solar system can be constrained by measuring the orbital distribution of the remnant planetesimals in the Kuiper belt. Determining the true orbit distribution is not simple because the detection and tracking of Kuiper belt objects (KBOs) is a highly biased process. In this chapter we examine the various biases that are present in any survey of the Kuiper belt. We then present observational and analysis strategies that can help to minimize the effects of these biases on the inferred orbital distributions. We find that material currently classified as the classical Kuiper belt is well represented by two subpopulations: a high-inclination component that spans and uniformly fills the stable phase space between 30 and 47 AU combined with a low-inclination, low-eccentricity population enhancement between 42 and 45 AU. The low-i, low-e component may be that which has long been called the "Kuiper belt." We also find weaker evidence that the high-i component of the classical Kuiper belt may extend beyond the 2:1 mean-motion resonance with Neptune. The scattering/detached disk appears to extend to larger semimajor axis with no evidence for a falloff steeper than r-1. This population is likely at least as large as the classical Kuiper belt population and has an i/e distribution much like that of the hot classical Kuiper belt. We also find that the fraction of objects in the 3:2 resonance is likely around 20% and previous estimates that place this population at ~5% are inconsistent with present observations. Additionally, high-order mean-motion resonances play a substantial role in the structure of the Kuiper belt.