Sketch of a hydrodynamic astrospherical shock configuration. The red lines denote the shocks, the blue lines stand for tangential discontinuities. The Mach numbers in the different regions are indicated by M ≷ 1. BS denotes the bow shock, TS the termination shock, SL is the sonic line, S_⋆ the position of the star, and C the middle point of an radius R_M describing the Mach disk MD. TD is the tangential contact discontinuity starting at the triple point T, where the reflected shock RS also starts.