演講資訊

摘要：

ust grains are formed in several types of near-stellar environment. However, once they enter the interstellar medium these grains will be modified in size, shape and even composition by a variety of physical processes. These modifying processes may continue to act throughout the lifetime of a grain. Thus, we should consider the possibility that grains evolve in the interstellar medium. In the diffuse medium, some materials will be affected by starlight or by cosmic rays, and some may be modified by chemical reactions with gas phase species. All grains will be eroded and possibly reduced to atoms or small molecular fragments in the intermittent passage of interstellar shock waves, with some materials (such as silicates) being more resistant to this kind of erosion than others (such as hydrocarbon polymers). The response of dust to local conditions may be reflected in the variations in interstellar extinction curves along different lines of sight in the Milky Way, and in other galaxies