heliopause

/ˈhiliəˌpɔz/

In astronomy, the heliopause is the outside edge or boundary of the heliosphere, the part of our solar system that's influenced by the sun. In 2012, NASA's Voyager 1 space probe crossed the heliopause.

Astronomers have various theories about what happens beyond the heliopause, at such a far distance from the sun that solar wind doesn't affect anything. Inside the heliopause is the heliosphere, and everything outside of the heliopause is considered interstellar space. The word heliopause is rooted in the Greek word for "sun," helios, and the Latin pausa, "a halt, stop, or cessation."

Definitions of heliopause

1. noun

   the boundary marking the edge of the sun's influence; the boundary (roughly 100 AU from the sun) between the interplanetary medium and the interstellar medium; where the solar wind from the sun and the radiation from other stars meet
   type of:

   bound, boundary, bounds

   the line or plane indicating the limit or extent of something