What is IBEX?

An artist’s conception of the IBEX spacecraft in orbit.

Image Credit: Walt Feimer (NASA GSFC)

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)Atoms with no charge that move very quickly. These atoms have equal numbers of positively-charged protons and negatively-charged electrons. ENAs form when charged particles from the solar wind travel outward and encounter atoms from the interstellar medium. Because the ENAs are neutral, they do not react to any magnetic fields. Some of these ENAs travel toward the inner solar system and are captured by the IBEX spacecraft.. 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 windA stream of charged particles, mostly protons and electrons, that escapes into the Sun's outer atmosphere at high speeds and streams out into the solar system. and the interstellar mediumAll the gas and dust found between stars.. The solar wind streams out into space and carves out a protective bubble around the Solar System called the heliosphereThe region around the Sun where the solar wind dominates over the interstellar medium..

CLICK TO PLAY MOVIE. Clip from IBEX: Search for the Edge of the Solar System.

Credit: NASA/Adler Planetarium.

What is IBEX?

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