  For stars, the bow shock is typically the boundary between their stellar wind
and the interstellar medium. Named for the wave made by a ship as it moves
through water, the bow shock wave can be created in the space when two streams
of gas collide. The space is actually filled with the interstellar medium
consisting of tenuous gas and dust. Stars are emitting a flow called stellar
wind. Stellar wind eventually bumps into the interstellar medium, creating an
interface where the physical conditions such as density and pressure change
dramatically, possibly giving rise to a shock wave. Here we discuss some
literature on stellar bow shocks and show observations of some of them,
enhanced by image processing techniques, in particular by the recently proposed
AstroFracTool software.
