A bow shock or wave will form in front of the heliosphereThe region around the Sun where the solar wind dominates over the interstellar medium., as the Sun moves through the interstellar mediumAll the gas and dust found between stars.. A bow wave is similar to what happens at the prow of a boat, while a bow shock is similar to the shockwave that forms in front of a supersonic jet.
If the Sun is moving faster than the speed of sound in the interstellar medium, a bow shock will form. Otherwise, if the Sun is not travelling that fast a bow wave will form.
