Astronomy and Astrophysics – Astronomy
Scientific paper
Sep 2011
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2011ess.....2.3315m&link_type=abstract
American Astronomical Society, ESS meeting #2, #33.15
Astronomy and Astrophysics
Astronomy
Scientific paper
We carry out three-dimensional Smoothed Particle Hydrodynamics simulations to determine the outcome of pre-planetesimal collisions of approximately 1-10 centimetre-sized silica dust aggregates. Previous laboratory results have investigated the threshold velocity above which dust aggregates shatter (e.g. Blum & Münch 1993; Teiser & Wurm 2009). However, detailed parameter studies are not possible in the laboratory. We perform a comprehensive study into the outcomes by considering the collision velocity, impact parameter, mass ratio and porosity of the aggregates to determine the conditions that allow them to grow into planetesimals. We also determine the properties of the largest and second largest fragments, as well as the fragmented population as done so in the four-population model introduced by Geretshauser et al. (2011). While previous studies often assume a threshold velocity of approximately 1m/s, recent experimental results suggest that higher threshold velocities (approximately 55m/s) may be possible.
Using high resolution SPH simulations, we find that the aggregate and collision properties significantly affect this value. We find that compact and highly porous objects are more prone to destruction as they are too fragile and too brittle, respectively, while intermediate porosity (approximately 65%) objects are more resistant to fragmentation. In addition, collisions between very different sized objects allow growth at larger velocities, at least as high as 20m/s. While collisions between medium porosity, unequal-sized aggregates is optimum for growth, all is not lost if destructive collisions occur: such collisions produce large and small fragments which may then collide and be recycled into aggregates that grow. Furthermore, the destruction of highly porous and compact aggregates in a series of collisions may produce medium porosity objects that can then be recycled into growing aggregates. This may have profound implications on planetesimal formation as the destructive collisions may counter-intuitively aid the growth of planetary cores.
This research is DFG funded.
Geretshauser Ralf J.
Kley Willy
Meru Farzana
Speith Roland
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