The early history of protostellar disks, outflows, and binary stars

TL;DR

This paper uses 3D simulations to show that early protostellar disks can form despite magnetic braking, revealing their structure, outflows, and implications for planet and binary star formation.

Contribution

It demonstrates that magnetic fields do not prevent early disk formation and explores the resulting disk and outflow structures in star formation.

Findings

Early disks form with high accretion rates despite magnetic braking.

Magnetic fields suppress gravitational instabilities in young disks.

Simulations reveal detailed disk density, temperature, and outflow structures.

Abstract

In star formation, magnetic fields act as a cosmic angular momentum extractor that increases mass accretion rates onto protostars and in the process, creates spectacular outflows. However, recently it has been argued that this magnetic brake is so strong that early protostellar disks -- the cradles of planet formation -- cannot form. Our three-dimensional numerical simulations of the early stages of collapse (\lesssim 10^5 yr) of overdense star--forming clouds form early outflows and have magnetically regulated and rotationally dominated disks (inside 10 AU) with high accretion rates, despite the slip of the field through the mostly neutral gas. We find that in three dimensions, magnetic fields suppress gravitationally driven instabilities which would otherwise prevent young, well ordered disks from forming. Our simulations have surprising consequences for the early formation of disks, their density and temperature structure, the mechanism and structure of early outflows, the flash heating of dust grains through ambipolar diffusion, and the origin of planets and binary stars.