RAPID COAGULATION OF POROUS DUST AGGREGATES OUTSIDE THE SNOW LINE: A PATHWAY TO SUCCESSFUL ICY PLANETESIMAL FORMATION

Journal Article · Wed Jun 20 04:00:00 EDT 2012 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/752/2/106· OSTI ID:22037012

Okuzumi, Satoshi; Kobayashi, Hiroshi ^[1]; Tanaka, Hidekazu ^[2]; Wada, Koji ^[3]

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1. Department of Physics, Nagoya University, Nagoya, Aichi 464-8602 (Japan)
2. Institute of Low Temperature Science, Hokkaido University, Sapporo 060-0819 (Japan)
3. Planetary Exploration Research Center, Chiba Institute of Technology, Narashino, Chiba 275-0016 (Japan)

Rapid orbital drift of macroscopic dust particles is one of the major obstacles to planetesimal formation in protoplanetary disks. We re-examine this problem by considering the porosity evolution of dust aggregates. We apply a porosity model based on recent N-body simulations of aggregate collisions, which allows us to study the porosity change upon collision for a wide range of impact energies. As a first step, we neglect collisional fragmentation and instead focus on dust evolution outside the snow line, where the fragmentation has been suggested to be less significant than inside the snow line because of the high sticking efficiency of icy particles. We show that dust particles can evolve into highly porous aggregates (with internal densities of much less than 0.1 g cm{sup -3}) even if collisional compression is taken into account. We also show that the high porosity triggers significant acceleration in collisional growth. This acceleration is a natural consequence of the particles' aerodynamical properties at low Knudsen numbers, i.e., at particle radii larger than the mean free path of the gas molecules. Thanks to this rapid growth, the highly porous aggregates are found to overcome the radial drift barrier at orbital radii less than 10 AU (assuming the minimum-mass solar nebula model). This suggests that, if collisional fragmentation is truly insignificant, formation of icy planetesimals is possible via direct collisional growth of submicron-sized icy particles.

• OSTI ID: 22037012
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 2 Vol. 752; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
ASTRONOMY
ASTROPHYSICS
COLLISIONS
COMPUTERIZED SIMULATION
COSMIC DUST
DENSITY
EVOLUTION
FRAGMENTATION
MEAN FREE PATH
PARTICLE RADII
PARTICLES
PLANETS
POROSITY
POROUS MATERIALS
PROTOPLANETS
SNOW
SOLAR NEBULA