IBEX is the first mission designed to map the entire boundary region at the edge of the solar system. As electrically charged particles from the sun (the solar wind) flow outward beyond the orbits of the planets, they collide with the material between the stars -- the interstellar medium, or ISM. These interactions create energetic neutral atoms (ENAs), fast-moving particles with no charge. This region emits no light that can be collected by conventional telescopes, so IBEX, measures the ENAs that happen to be traveling inward from the boundary. IBEX's sole science objective is to discover the nature of the interactions between the solar wind and the interstellar medium at the edge of our solar system. The mission launched in 2008.