Planetesimal formation by sweep-up: how the bouncing barrier can be beneficial to growth

By F. Windmark, T. Birnstiel, C. Guttler, J. Blum, C. Dullemond, Th. Henning. 2012

176 citations recorded by the source corpus.

Context. The formation of planetesimals is often accredited to the collisional sticking of dust grains. The exact process is unknown, as collisions between larger aggregates tend to lead to fragmentation or bouncing rather than sticking. Recent laboratory experiments have however made great progress in the understanding and mapping of the complex physics involved in dust collisions. Aims. We study the possibility of planetesimal formation using the results of the latest laboratory experiments, particularly by including the fragmentation with mass transfer effect, which might lead to growth even at high impact velocities. Methods. We present a new experimentally and physically motivated dust collision model capable of predicting the outcome of a collision between two particles of arbitrary mass and velocity. The new model includes a natural description of cratering and mass transfer, and provides a smooth transition from equal- to different-sized collisions. It is used together with a continuum dust-size evolution code, which is both fast in terms of execution time and able to resolve the dust at all sizes, allowing for all types of interactions to be studied without biases. Results. For the general dust population, we find that bouncing collisions prevent any growth above millimeter-sizes. However, if a small number of cm-sized particles are introduced, for example by either vertical mixing or radial drift, they can act as a catalyst and start to sweep up the smaller particles. At a distance of 3 AU, 100-m-sized bodies are formed on a timescale of 1 Myr. Conclusions. Direct growth of planetesimals might be a possibility thanks to a combination of the bouncing barrier and the fragmentation with mass transfer effect. The bouncing barrier is here even beneficial, as it prevents the growth of too many large particles that would otherwise only fragment among each other, and creates a reservoir of small particles that can be swept up by larger bodies. However, for this process to work, a few seeds of cm-size or larger have to be introduced.

Subfields: Astronomy and Astrophysics, Geophysics

View Paper: https://www.semanticscholar.org/paper/4c90a46a241ebdc14a3bc76edb5efd6f6c21e124

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Citations in the corpus

The primordial nucleus of comet 67P/Churyumov-Gerasimenko (2015, background): “According to Windmark et al. (2012a) these large aggregates can grow from smaller ones if the collisions are violent enough to fragment the small ones but gentle enough not to erode the large ones.”
Breaking through: The effects of a velocity distribution on barriers to dust growth (2012, methodology): “Windmark et al. (2012) suggested a sweep-up scenario where the fragmentation barrier can be circumvented.”
The Disk Substructures at High Angular Resolution Project (DSHARP). V. Interpreting ALMA Maps of Protoplanetary Disks in Terms of a Dust Model (2018, methodology): “Given the uncertainty in the details of collision models (see, Güttler et al. 2010; Windmark et al. 2012, for example), and for ease of reproduction, we will be using the B11S fits in the following.”
Ring shaped dust accumulation in transition disks (2012, background): “In fact, Windmark et al. (2012) showed that with the insertion of cm-sized seeds, considering mass transfer processes and bouncing, at a distance of few AU, small dust can grow to ∼ 100 meters on timescales of 1 Myr.”
Evidence for the formation of comet 67P/Churyumov-Gerasimenko through gravitational collapse of a bound clump of pebbles (2017, background): “This rules out any collisionalgrowth-only models for planetesimals (see, e.g., Windmark et al. 2012), which rely on mass accretion in high-velocity impacts, because they compress the material to its densest state of φ ≈ 0.4 (Güttler et al. 2010) and lead to too high tensile strengths and bulk…”
How to form planetesimals from mm-sized chondrules and chondrule aggregates (2015, background): “For example, bodies at 3 au can grow to a maximum of 100 m in 1 Myr (Windmark et al. 2012).”
Dust Evolution and the Formation of Planetesimals (2016, methodology): “Particles will continue to grow beyond the bouncing barrier, as found by Windmark et al. (2012b).”
Forming the cores of giant planets from the radial pebble flux in protoplanetary discs (2014, background): “This prevents continued particle growth by coagulation (Brauer et al. 2008), except possibly in the inner disc with large particle seeding (Windmark et al. 2012) or porous dust aggregates (Kataoka et al. 2013).”
Rapid growth of gas-giant cores by pebble accretion (2012, background): “Particle growth beyond cm-sizes by coagulation is inefficient (Blum & Wurm 2008; Brauer et al. 2008; Windmark et al. 2012) and radial drift timescales for m-sized boulders are as short as a hundred orbital timescales (Adachi et al. 1976; Weidenschilling 1977).”
Fluffy dust forms icy planetesimals by static compression (2013, background): “Several possibilities have been proposed to overcome these barriers (Johansen et al. 2007; Pinilla et al. 2012; Windmark et al. 2012; Lambrechts & Johansen 2012; Ros & Johansen 2013; Garaud et al. 2013).”
Ice Condensation as a Planet Formation Mechanism (2013, background): “For silicate particles growth via collisions involving equal-sized particles is very difficult beyond millimeters, however collisional growth involving small particles colliding with a large target is possible, although slow (Wurm et al., 2005; Johansen et al., 2008; Windmark et al., 2012).”