What is IBEX?
IBEX is a NASA-funded satellite, a Small Explorer mission to map the boundary of the Solar System. The acronym IBEX stands for “Interstellar Boundary Explorer”. The spacecraft is the size of a bus tire. It orbits the Earth and collects particles called “energetic neutral atoms” (ENAs), particles with no charge that move very fast. The boundary is created by the interaction between particles from the Sun that are streaming outward, called the “solar wind”, and material between the stars, called the “interstellar medium”. Outer space is not empty space. The interstellar medium (ISM) is the name for the stuff that is in space between stars in our Milky Way Galaxy. This stuff is mostly made of clouds of hydrogen and helium, though there are heavier elements like carbon, and one percent of the ISM is in the form of dust. The solar wind streams out into space and carves out a protective bubble, called the “heliosphere”, in the ISM around our Solar System. IBEX maps the solar wind particles t
