As charged particles flow out from the sun, they eventually bump up against interstellar medium—the relatively empty areas between stars. These interactions "inflate" a protective bubble that shields Earth and the entire solar system from potentially harmful cosmic rays (solar system pictures).

Now IBEX has surprised astronomers by showing that this force field-like structure, the heliosphere, is an unexpectedly dynamic, unpredictable boundary.

"If we've learned anything from IBEX so far, it is that the models that we're using for interaction of the solar wind with the galaxy were just dead wrong," David McComas, principal investigator for the IBEX program, said during a NASA press conference Thursday.

For starters, it's been assumed that the heliosphere's expansion and contraction follows the sun's roughly