NASA’s Interstellar Boundary Explorer (IBEX) mission, called “Journey to the Edge of the Solar System”, is  to be launch in 2008. IBEX will make the first global map of the boundary between the solar system and interstellar space, which is about 100 times farther away from the Sun than the Earth, Only two spacecraft in history have operated long enough in space to reach  that region — Voyager 1 and Voyager 2 — but neither carried the proper instruments to measure in-situ the properties of the boundary. An invisible “termination shock”,  the outer edge of the solar system, is located at this distance. This plasma shock front is created in much the same way that an air shock forms in front of a supersonic aircraft as it flies through the air. The wave of plasma deflects ionized interstellar material and shields the solar system from harmful radiation of cosmic ways streaming between the stars. Scientists do not know the exact nature of the termination shock, its shape, and what happens to the solar matter that crosses the shock. Ibex will  study these properties.