The early stages of planet formation: how to grow from small to large

The protoplanetary disk is the place where small, micron-size dust grains will coagulate into planets. This dissertation concerns the first stages of the
condensation process, i.e., the growth of these dust grains into planetesimals -- objects ~1 km in size. A few aspects of the coagulation are studied in detail.

When they are small, dust grains stick easily together due to strong intermolecular forces that operate between them. The result is the formation of grain clusters or dust aggregates. However, if these aggregates reach macroscopic sizes (mm to cm) their sticking capabilities are much reduced. Besides, relative velocities between the dust particles increase. The formation of the planetesimals is not a trivial process.

In this thesis the growth process is modeled by Monte Carlo simulations. The advantage of this method is that the collision behavior of dust particles can be followed individually. In this way the simulations are directly linked to experimental collision experiments. However, to reach the large dynamic ranges required to model the great diversity of particles, the method has been significantly expanded.

Some conclusions that follow out of the thesis are as follows: (i) Due to their open, fractal structure, dust aggregates are well coupled to the gas, which somewhat reduces the effects of gravity. (ii) A porous structure may act as an important counterforce against energetic collisions. (iii) Micron-size dust particles are important in the aggregation of chondrules -- the building blocks of meteorites. (iv) Dust aggregation could already have been initiated in the molecular cloud environment.

	Title and contents
	Chapter 1
	Chapter 2
	Chapter 3
	Chapter 4
	Chapter 5
	Chapter 6
	Chapter 7
	Glossary
	List of symbols
	Color figures
	Nederlandse samenvatting
	Acknowlegdments
	Complete thesis

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