Planetesimal formation in turbulent protoplanetary discs
by
MrAnders Johansen(Max-Planck-Institut für Astronomie, Heidelberg)
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Europe/Stockholm
FA31
FA31
Description
The planetesimal hypothesis for planet formation suggests that dust grains in
protostellar discs collide to form ever larger bodies. Coagulation allows
growth from micron-sized interstellar grains to metre-sized boulders, but gas
drag causes boulders to quickly spiral into the protostar. Formation of
kilometre-sized planetesimals must occur first, but a viable mechanism remains
lacking. I present work I have done on planetesimal formation during my PhD.
Dust boulders are concentrated by up to a factor 100 in transient high pressure
regions that form spontaneously in the turbulent discs. A powerful linear
instability in the coupled flow of solids and gas leads to even more clumping
of the boulders. We have performed the most advanced simulations yet of the
sedimented mid-plane layer of solids where we include drag force, turbulence, a
spectrum of particle radii, collisional cooling and the self-gravity between
the boulders. Extremely dense, gravitationally bound clusters of boulders
condense out of the overdense regions, with masses that are nine orders of
magnitude larger than what is normally thought for planetesimals. This process
can occur even in discs that are comparable in mass to the minimum mass solar
nebula.
