Comparison of the path stellar radiation (a) and radiation originating from thermal re-emission (b) take toward the point of scattering and the path they take after scattering (c). The path the radiation would take without scattering is illustrated with a dashed line. The difference of the scattering angles for stellar radiation and scattered thermal re-emission radiation is denoted as γ. For details, see Sect. 3.2.1.