- It is an astrographic feature.
- It extends beyond the orbit of the outermost planet of a system.
- It extents far past the Kuiper Belt region, if the system has one, but generally terminates before the Oort Cloud.
- It is also known as the Hill Sphere.
Plasma "blown" out from the star, known as the solar wind, creates and maintains a bubble or cavity against the outside pressure of the interstellar medium, the hydrogen and helium gas that permeates the Galaxy.
The termination shock is the boundary marking one of the outer limits of the star's influence. It is the region where the bubble of solar wind particles begin to press into the interstellar medium and slow down, so that they are traveling slower than the speed of sound relative to the star.