What is the boundary where the solar wind is stopped by interstellar space called? The heliopause. It is the outer boundary of the heliosphere, where the outward pressure of the solar wind balances the surrounding interstellar medium.
The Sun constantly releases charged particles and magnetic fields in a flow called the solar wind. This creates a vast bubble around the Solar System. Far from the Sun, the wind becomes weaker, while interstellar gas, plasma, magnetic fields, and cosmic rays exert increasing pressure from outside.
Before reaching the heliopause, a spacecraft passes the termination shock, where the solar wind abruptly slows and becomes hotter. The region between that shock and the heliopause is called the heliosheath. Beyond the heliopause lies interstellar space, though the Sun’s gravity still extends much farther.
The heliopause is not a perfectly fixed shell: its distance changes with solar activity and varies by direction. It is often confused with the magnetopause, which is the boundary around a planet’s magnetic field, especially Earth’s, rather than the edge of the Sun’s heliosphere.