Thanks. I think this part describes why: http://en.wikipedia.org/wiki/Heliosphere#Heliopause http://en.wikipedia.org/wiki/Heliosphere#Heliopause The heliop

Thanks. I think this part describes why: http://en.wikipedia.org/wiki/Heliosphere#Heliopause http://en.wikipedia.org/wiki/Heliosphere#Heliopause The heliopause is the theoretical 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.