The Inner Kernel of the Classical Kuiper Belt

TL;DR

This paper identifies a new structure in the classical Kuiper belt, called the inner kernel, using clustering algorithms on orbital data, which may be a distinct feature or an extension of the previously known kernel.

Contribution

The study applies clustering algorithms to barycentric free orbital elements to discover the inner kernel in the Kuiper belt, expanding understanding of its structure.

Findings

Discovery of the inner kernel at ~43 AU in the Kuiper belt.

Recovery of the previously known kernel at ~44 AU.

Potential for future observations to clarify the nature of these structures.

Abstract

The `kernel' of the classical Kuiper belt was discovered by Petit et al. (2011) as a visual overdensity of objects with low ecliptic inclinations and eccentricities at semimajor axes near 44 AU. This raises the question - are there other structures present in the classical Kuiper belt? If there are, clustering algorithms applied to orbits transformed into free elements may yield the best chance of discovery. Here, we derive barycentric free orbital elements for objects in the classical Kuiper belt, and use the Density-Based Spatial Clustering of Applications with Noise (DBSCAN) algorithm to identify a new structure, which we dub the inner kernel, located at $a \sim 43 \mathrm{\; AU}$ just inward of the kernel ($a \sim 44 \mathrm{\; AU}$), which we also recover. It is yet unclear whether the inner kernel is an extension of the kernel or a distinct structure. Forthcoming observations, including those by the Vera C. Rubin Observatory's Legacy Survey of Space and Time (LSST) may provide further evidence for the existence of this structure, and perhaps resolve the question of whether there are two distinct structures.