Applications: Cosmic Dust Grains

Abstract

The importance of the cosmic dust forming the interstellar medium (ISM) has long been recognized in astronomy. The interaction of the cosmic dust grains with the radiation field of the stars, beyond yielding extinction and polarization of the starlight by linear dichroism, also yields mechanical interactions such as the radiation pressure and the radiation torque that, together with the gravitational interactions, determine the dynamics of the grains themselves. According to Chaps. 4 and 7, all these phenomena, both optical and mechanical, can be traced back to the transition matrix of the dust grains. Moreover, the technique of Sect. 5.5 is appropriate to investigate also the state of polarization of the electromagnetic radiation that penetrates into the cavities contained in the interstellar dust grains. Therefore, a great deal of information could be gained by applying to the ISM the methods and procedures that have been expounded in the preceding chapters. Accordingly, this chapter is devoted to the discussion of some astrophysical problems which we deal with through the theory of electromagnetic scattering.