The heliopause is the boundary where the Sun's solar wind is stopped by the interstellar medium; where the solar wind's strength is no longer great enough to push back the stellar winds of the surrounding stars. The crossing of the heliopause is signaled by a sharp drop in the temperature of charged particles, a change in the direction of the magnetic field, and an increase in the amount of galactic cosmic rays .
Until 3012 (OTT) no clear definition was set where the boundaries of a local star and its systems are. Some societies claimed it is the outmost orbit of the last object in orbit around the local star. Some insisted it is the Heliosphere and a few wanted it to be the Heliopause.
The Union Conference on Interstellar boundaries in 3012 determined the boundaries of planets, moons and star systems. The definitions found were accepted as Union Law by Assembly vote and became the Interstellar Boundry Act of 3012 .
Note : Pre Astro - Historic refrence -Earth scienceEdit
In May 2012, Voyager 1 detected a rapid increase in such cosmic rays (a 9% increase in a month, following a more gradual increase of 25% from Jan. 2009 to Jan. 2012), suggesting it was approaching the heliopause. In the fall of 2013, NASA announced that Voyager 1 had crossed the heliopause as of August 25, 2012. This was at a distance of 121 AU (18 billion km) from the Sun .