planetesimal formation: when, where, how many? formation: when, where, how many? lund 07-05-2015...
TRANSCRIPT
Planetesimal formation: when, where, how many?
Lund07-05-2015
collaboration:Kees DullemondFredrik WindmarkSatoshi Okuzumi
Joanna Drążkowska
Introduction
plan
ets!
Growth barriers
collisional radial drift● bouncing: mm- to cm-size● fragmentation: cm- to m-size
● m-size at 1 AUmm-size at 100 AU
Pressure bump (+ sweep-up growth)
● Only <1% of dust particles are able to grow to planetesimal sizes
● Planetesimal formation only in the pressure bump
● Timescale of planetesimal growth: ~105 yrs
Drążkowska+ 2013, see also: Brauer+ 2008, Haghighipour 2005
Drążkowska, Windmark & Okuzumi 2014
Sweep-up growth triggered by the impact velocity distribution
● Planetesimal formation is local and happens only inside of 1 AU● ~4% of dust turned to planetesimals● Growth is very fast, some planetesimals form in 100 yrs
Previous SI models: heavy hydrodynamical simulations with restricted size distributions
Streaming instability
● Planetesimal formation is only possible outside the snow line (due to the bouncing barrier)
Streaming instability
● Planetesimal formation requires enhanced metallicity and/or reduced pressure support => pressure bumps!
dust
-to-
gas
ratio
(pressure gradient)
Streaming instability
● It does never happen that 100%of dust is turned to planetesimals, typical value is 10%
Streaming instability
Drążkowska & Dullemond 2014
Summary
This picture is very different from what is used as the working hypothesis for planetesimal accretion and planet population synthesis models!
1. Drążkowska, Windmark & Dullemond 2013, A&A, 556, A37 2. Drążkowska, Windmark & Dullemond 2014, A&A, 567, A383. Drążkowska, Windmark & Okuzumi 2014, Proceedings of the IAUS 3104. Drążkowska & Dullemond 2014, A&A, 572, A78