2007 Fiscal Year Final Research Report Summary
Theoretical Studies on Evolution of Dust Size and Structure in Protoplanetary Disks
| Project/Area Number |
18540227
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Astronomy
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| Research Institution | Hokkaido University |
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Principal Investigator |
TANAKA Hidekazu Hokkaido University, Institute of Low Temperature Science, Associate Professor (00282814)
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| Co-Investigator(Kenkyū-buntansha) |
WADA Koji Hokkaido University, Institute of Low Temperature Science, Postdoctoral Fellow (10396856)
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| Project Period (FY) |
2006 – 2007
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| Keywords | planet formation / protoplanetary disk / dust grain / bulk density / planetesimal / フラクタル構造 |
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| Research Abstract |
The bulk density of dust aggregates is an important factor in collisional growth of dust in protoplanetary disks. The density of aggregates changes the coupling with the disk gas, which governs the motion of aggregates in disks. Collisional outcomes also depend on the aggregate density. We perform three-dimensional N-body simulations of sequential collisions of aggregates composed of a number of sub-micron-sized icy particles in order to investigate the density evolution of dust aggregates growing in protoplanetary disks. In the present simulation of sequential collisions, as the initial aggregates at each collision, we use the resultant aggregate obtained at the previous collision. By repeating N-body calculations of aggregate collisions, we examined the density evolution of aggregate collisions. At an early stage of dust growth, aggregates stick to each other without restructuring, and the density of these aggregates decreases. At a later stage, in which the impact energy exceeds a critical energy, aggregates are gradually compressed. The compressed aggregates have a fractal dimension of 2.5. Because of this small fractal dimension, their density remains very low even at this compression stage. We also derive an equation describing the density evolution of growing aggregates. Applying this equation to dust growth in protoplanetary disks, we find that dust aggregates have an extremely low density (< 0.1 kg m-3). In the simulation of the present study, we consider only head-on collisions. The effect of oblique collisions would further reduce the aggregate density.
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[Presentation] A 3-D numerical simulation of dust aggregate collisions2006
Author(s)
Wada, K., Tanaka, H., Suyama, T., Kimura, H., and Yamamoto, T.
Organizer
Asia Oceania Geosciences Society 3rd Annual Meeing
Place of Presentation
SuntecSingapore InternationalConvention & Exhibition Centre,Singapore
Year and Date
2006-07-11
Description
「研究成果報告書概要(欧文)」より
