A New Growth Model for Protoplanetary Dust Aggregates Carsten Güttler & Jürgen Blum Institut für...

A New Growth Model for Protoplanetary Dust

Aggregates

Carsten Güttler & Jürgen BlumInstitut für Geophysik und extraterrestrische Physik,

TU Braunschweig, Germany

Dust in Planetary SystemsFriedrich Schiller Universität, Jena

September 27th to October 1st 2010

PRESENTATION WITHOUT MOVIE FILES. PLEASE REQUEST FROM [email protected] OR [email protected]

Güttler & Blum: A New Growth Model for Protoplanetary Dust Aggregates

From Dust to Planets

dust~1 µm

planetesimals e.g. 1 km

agglomerationInteraction with gas dominant

gravitation negligible

Blum et al.,1998

Dominik & Tielens, 1997see also: Blum & Wurm, 2000

?

Comet Temple 1© NASA/JPL-Caltech/UMD

Poppe et al., 2000a

Poppe et al.,2000a


Outline

1. The Collision Modellaboratory experiments

2. Results: Application of the Modelconsequences for the evolution of dust

3. Discussion of Resultscritical inspection of the model

4. New Experimentsfuture improvements of the model


1. Overview on Collisional Outcomes

Güttler et al., 2010


1. Overview on Collisional Outcomes



S1: Hit & Stick

Sticking without any restructuring ifEimpact < 5 · Eroll

Physical description and simulation:Dominik & Tielens (1997)

Experiments:Blum & Wurm (2000)

Blum & Wurm,2000

Blum & Wurm, 1998

Blum et al.,1998


S2: Sticking by Surface Effects

Collisions can lead to sticking although the hit-and-stick threshold velocity is exceeded

Explanation: aggregate is compacted, contact area increases→ more contacts support sticking

size: 0.2 mm; velocity: 0.24 m/s

Kothe, Güttler & Blum,unpublished data


B1: Bouncing with Compaction I

Collisions betweenmm-sizedaggregates hardlylead to sticking

Bouncing for low velocities (<1m/s)

Heißelmann, Fraser & Blum, 2007

5 mmvrel = 0.4 m/s


B1: Bouncing with Compaction II

Weidling et al., 2009

3 mm


1. Possible Collisional Outcomes


The Collision Model

x axes: velocity10-4 .. 104 cm/s

y axes: mass10-11 .. 102 g


1. The Collision Model


Outline






2. The Monte-Carlo Growth Model

Dust growth in a box in the protoplanetars disk Fast Monte Carlo code (Zsom & Dullemond, 2008) Aggregates possess physical properties (i.e. mass,

porosity), which determine the collisional outcome Monte Carlo character:

collision probabilitiesdetermine the nextcollision to compute

Model parameters:r=1AU; α=10-4; T=200K;Σ0=1700 g/cm2 (MMSN)


2. Which Collisions Do Really Occur?

Dust growth in a box in the protoplanetary disk(Zsom & Dullemond, 2008)

Model parameters:r=1AU; α=10-4; T=200K; Σ0=1700 g/cm2 (MMSN)

Zsom et al., 2010


2. How do the Aggregates Grow?

Mass Evolution max ~1g Bouncing inhibits

further growth

Porosity Evolution very fluffy aggregates

after ~1000 years Bouncing compacts

aggregates

Zsom et al., 2010


2 .Overview of Collisions

Many collisions do not occur within the experiment-boxes

Extrapolations by orders of magnitude

New experiments are being designed to check the 'hot-spots'

Zsom et al.,2010


Outline






Sizes of protoplanetary dust aggregates:

Mass ratios of projectile and target:

Collision velocities of protoplanetary dust aggregates:

Porosities of protoplanetary dust aggregates:

Protoplanetary dust materials and temperatures:

1 µm 1 mm 1 kmx 1 m

10-4 m/s 10-2 m/s 100 m/sx1 m/s

oxides/metals >1000 K

silicates~300 K

ices~100 K

organics~200 K

no expt’s expt’s

compact very porousxporous

0 1x

3. How Complete is the Model?


3. How Solid are the Threshold Lines?

experiments andMD simulations

model based onHertzian theory

base

d o

nexperi

ments

bouncing dominates

porosity modelexclusively basedon Weidling et al.


3. Improvement of Monte Carlo Method

Previous simulations in a local, static box (no global particle motion) 0D

Recent simulations with many boxes, including differential settling and turbulent mixing 1D


Zsom, Ormel, Dullemond & Henning, in prep.

midplane

1 pressurescale height

2 pressurescale heights


Outline






4. Sticking and Bouncing



4. Collisional Outcomes

Weidling et al., unpublished

Microgravity experiment(drop tower, suborbital flight)

Particle diameter:0.5-1.5 mm

Initial velocity ~0.1m/s

Collisional cooling down to mm/s


Two bouncing collision

v = 17 cm/s (first)v = 14 cm/s (second)

particle size: 0.5-1.5 mm

4. Bouncing I

particle diameter: 1 mmfilling factor: 40%

47 analyzed collisions:• 6x sticking• 40x bouncing• 1x fragmentation



Bouncing collision

v = 12 mm/s

particle size:0.5-1.5 mm

4. Bouncing II





Sticking collision

v = 9 mm/s

particle size:0.5-1.5 mm

4. Sticking





4. Relation to Collision Model

scheduledfor 11/2010

to beanalyzed



4. Bouncing and Fragmentation


4. Laboratory Drop Tower

Laboratory drop tower

Two aggregates collide in free fall

Two falling cameras, 1.5 m drop height

Velocities from1 cm/s to 3 m/s

Beitz et al., in prep.


4. Low-Velocity Collisions

2cm diameter, 50% fillingfactor, velocity: 10 mm/s

2cm diameter, 50% filling factor, velocity: 1.8 m/s


4. Fragmenting Collisions

bouncing forv < 20 cm/s

fragmentation with mass transfer forv > 20 cm/s


also see poster byJens Teiser et al.


4. Revised Fragmentation Threshold?



4. Fragmentation with Mass Transfer

Kothe, Güttler & Blum,accepted by ApJ


Kothe, Güttler & Blum,accepted by ApJ

4. Fragmentation with Mass Transfer II

Thank you foryour attention!

This work was funded by the Deutsche Forschungs-gemeinschaft (DFG) under grant Bl 298/14-1 and

by DLR under grant 50WM0936.

We thank René Weidling, Eike Beitz, and Stefan Kothefor providing their unpublished data.

Additional information on the presented model can be found in Güttler et al. (2010, A&A) and Zsom et al. (2010, A&A).

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A New Growth Model for Protoplanetary Dust Aggregates Carsten Güttler & Jürgen Blum Institut für...

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