IBEX is a small explorer NASA mission to map the boundary of the Solar System. The acronym IBEX stands for Interstellar Boundary EXplorer. Watch a short introductory movie about IBEX.

The IBEX spacecraft is a small satellite the size of a bus tire. IBEX will observe the Solar System Boundary while in orbit around Earth. It has "telescopes" on the spacecraft that will look out towards the edge of the Solar System. However, these telescopes are different than most telescopes. They collect particles instead of light. These particles are called energetic neutral atoms (ENAs). The ENAs will provide information about the Solar System’s boundary by travelling toward Earth from beyond the orbit of Pluto. The particles travel for as little as a month to up to 11 years to complete the journey. By collecting these particles, scientists can make the first map of the boundary of our Solar System. This boundary is created by the interaction between the solar wind and the interstellar medium. The solar wind streams out into space and carves out a protective bubble around the Solar System called the heliosphere.