Top-down planet formation: the crucial role of magnetic fields

by Dr Hongping Deng (University of Cambridge)

Tuesday 2 Nov 2021, 10:00 → 11:00 Asia/Shanghai

TDLI Meeting Room 200

Abstract

There is accumulating evidence about early planet formation. Protoplanetary disks as young as 0.5 Myr bear gaps and rings, although rings/gaps are not definitive signposts of baby planets. However, we suggest warps in protoplanetary disks are likely maintained by planets. Anyway, the evolution of young disks is crucial to our understanding of planet formation. In the early stages, the disk is unstable due to gas self-gravity and spiral density waves feature. Spirals can drive large-scale vertical circulations and amplify any seed magnetic fields to nearly thermal amplitudes. This dynamo is vigorous even in poorly ionized regions of the protoplanetary disk. If the spiral collapses due to efficient cooling, the magnetic fields will wrap up the fragment and effectively isolate the fragment from the turbulent disk. We found fragments as light as Neptune survive in disks thanks to the protection of magnetic fields. They may later capture solids in their cores, and thus a rapid top-down formation is possible for major types of planets. We are aiming at more realistic simulations with radiative transfer and dust gas interactions.

Biography

2010-2014 Tsinghua University, B.S. in Physics
2015-2019 University of Zurich, PhD in astrophysics
2019-2021 DAMTP, University of Cambridge, postdoc (research fellow)

Chair

Fabo Feng

Division

Astronomy and Astrophysics

Other information

Video link:  https://vshare.sjtu.edu.cn/play/96bd9ee394001b6ccaf03c289ea077a6