A bow shock is a bow-shaped shock wave caused by an object moving through a surrounding medium at higher than the speed of sound. It is in front of the object rather than touching it. A supersonic jet causes a bow shock in the atmosphere. A star or planet (e.g., Earth) can cause a bow shock in the medium around its magnetosphere. The solar system was assumed to cause such a shock but recent data suggests it does not, implying that the relative speed of the solar system through the surrounding medium is subsonic.