In one of those weird coincidences I came across the word heliopause for the firt time today - Here. Then it cropped up again in an article that caught my eye about the space probe "Voyager" -

"There are multiple ways to think about the “edge of the solar system.” One is a boundary region called the heliopause. That’s the frontier where the solar wind (the soup of charged particles continually thrown off by the sun) is too weak to hold off the interstellar medium—the plasma, dust, and radiation that fill the bulk of space."

Well I never :-)