The Voyager 1 and 2 spacecraft have traveled beyond the edges of the bubble in space where the sun's constant outward wind of particles and radiation slams into the interstellar medium that pervades our galaxy. Because they are leaving the solar system on paths that are about 45 degrees apart, the data reveals details about the shape of the bubble created by the solar wind. The fact that they crossed the edge of the solar outflow--a region called the boundary shock--at different distances out from the sun proved that this bubble is squashed rather than being a symmetrical sphere. via MIT