Planetesimals on eccentric orbits erode rapidly

TL;DR

This study combines theory and simulations to show that planetesimals on eccentric orbits in protoplanetary disks erode rapidly, with erosion rates largely independent of flow conditions and initial shape.

Contribution

It introduces a universal power-law model for erosion of large bodies in gas flows and applies it to estimate erosion timescales for planetesimals in different orbital configurations.

Findings

Erosion follows a universal power-law over time.

Planetesimals in inner disks erode within about a hundred years.

Even circular orbit planetesimals erode in roughly ten thousand years.

Abstract

We investigate the possibility of erosion of planetesimals in a protoplanetary disk. We use theory and direct numerical simulations (Lattice Boltzmann Method) to calculate the erosion of large -- much larger than the mean-free-path of gas molecules -- bodies of different shapes in flows. We find that erosion follows a universal power-law in time, at intermediate times, independent of the Reynolds number of the flow and the initial shape of the body. Consequently, we estimate that planetesimals in eccentric orbits, of even very small eccentricity, rapidly (in about hundred years) erodes away if the semi-major axis of their orbit lies in the inner disk -- less than about $10$ au. Even planetesimals in circular orbits erode away in approximately ten thousand years if the semi-major axis of their orbits are $\lessapprox 0.6$au.