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IBEX mission graphic

Interstellar Boundary Explorer

Phase: Operating

Launch Date: October 19, 2008

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Program(s):Explorers, Heliophysics Research

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IBEX is the first mission designed to map the entire region of the boundary of our Solar System. As charged particles from the Sun, called the "solar wind," flow outward well beyond the orbits of the planets, they collide with the material between the stars, called the "interstellar medium" (ISM).  These interactions create energetic neutral atoms (ENAs), particles with no charge that move very quickly. This region emits no light that can be collected by conventional telescopes so, instead, IBEX, measures the particles that happen to be traveling inward from the boundary.  IBEX contains two detectors designed to collect and measure ENAs, providing data about the mass, location, direction of origin, and energy of these particles.  From this data, maps of the boundary are created.  IBEX's sole, focused 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.

Over the course of a two-year mission, IBEX will answer four fundamental science questions: 

  • What is the global strength and structure of the termination shock?
  • How are energetic protons accelerated at the termination shock?
  • What are the global properties of the solar wind flow beyond the termination shock and in the heliotail?
  • How does the interstellar flow interact with the heliosphere beyond the heliopause?