IBEX = Interstellar Boundary Explorer, launched October 19, 2008
It's purpose is to discern the several boundaries created by the outward solar wind "force field" pushing towards interstellar space.
The 'Termination Shock' demarcation is where the solar wind slows down, becomes more dense, and is diverted away on its journey towards the galactic material of interstellar space.
Beyond that is the 'Heliopause boundary' which separates the galactic material of outer interstellar space from the material of inner solar origin.
Finally, there's the 'Bow Shock' out in front of the quickly moving solar wind interacting with the outer galactic material of interstellar space.
In effect, the outwardly pushing solar wind acting as a sort of "force field" protects Earth and any future space travelers to Mars, say, from any harmful galactic cosmic rays which are radiation coming from distant parts of the Milky Way and beyond.
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