Growing Planetesimals

Details Growing Planetesimals Growing Planetesimals

Sep 2009

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2009dps....41.4003w&link_type=abstract

American Astronomical Society, DPS meeting #41, #40.03

Astronomy and Astrophysics

Astronomy

Scientific paper

Dust in protoplanetary disks forms km-size planetesimals. Just how this proceeds is still an unsettled question. Collisions among the µm to sub-km size bodies do occur and assuming these lead to the growth of larger bodies is the most straight forward assumption.
However, collisional speeds are up to 100 m/s. Is it possible that these ,,high speed“ collisions are constructively leading to larger bodies?
In recent laboratory experiments we studied the collisions between dust aggregates consisting of micron size particles at intermediate and high speed. We find that at intermediate speed up to 10 m/s compact dust aggregates form. Gas drag aided reaccretion is an important factor for efficient growth here. At high speeds of several tens of m/s collisions of a larger compact dust aggregate with a sub-mm dust aggregate lead to net growth of the larger body, while collisions with cm projectiles lead to a small amount of erosion. In detail the threshold size between growth and erosion depends on the collision velocity. The damage of the target is limited to a local extent though and ejecta are smaller than the original projectile. A cascade of collisions would produce ever smaller ejecta. Eventually, the ejecta are small enough that further collisions lead to growth again.
This way growth of larger bodies in a fragmentation / aggregation cascade is possible.
This work is funded by the Deutsche Forschungsgemeinschaft.

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