The Roles of Dust in the Formation of Stars and Planets
Dust influences star formation in various ways. The process of star formation is observed to occur only in dense dark clouds of interstellar gas, so the first requirement is that the process is shielded from ambient starlight. Dust grains are effective coolants of interstellar gas, and so help the gravitational collapse of dust clouds by maintaining a low gas temperature. Dust grains also influence the formation and loss of gaseous molecules that also contribute to cooling and hence to star formation. In cases in which the dust grains become the dominant carriers of charge inside dark regions, they effectively control the ambipolar diffusion timescale and therefore the support available to the region from the magnetic field. Dust grains provide the basic solid materials from which planets are formed. The initial step in this process is the collision and sticking of dust grains that occurs in high density gas. The probability of sticking is significantly affected by the physical and chemical nature of the material of the dust grains.