Formation of the First Planetesimals via the Streaming Instability in Globally Turbulent Protoplanetary Disks?

TL;DR

This study uses self-consistent turbulent models of protoplanetary disks to evaluate conditions for streaming instability-driven planetesimal formation, finding that such conditions are not met during the critical early million years.

Contribution

It demonstrates that the local metallicity and Stokes number criteria for streaming instability are generally not achieved in early disk evolution, challenging previous assumptions about planetesimal formation timing.

Findings

Streaming instability criteria are not met in early disk stages.

First planetesimals likely form through alternative mechanisms.

Implications for timing of planet formation processes.

Abstract

Using self-consistent models of turbulent particle growth in an evolving protoplanetary nebula of solar composition we find that recently proposed local metallicity and Stokes number criteria necessary for the streaming instability to generate gravitationally bound particle overdensities are generally not approached anywhere in the disk during the first million years, an epoch in which meteoritic and observational evidence strongly suggests that the formation of the first planetesimals and perhaps giant planet core accretion is already occurring.