The bubble of space around the Sun within which the solar wind flows. The heliosphere is about 120 au in radius and is bounded by the heliopause, beyond which interstellar gas exerts an equal pressure from outside. The shape of the heliosphere is unknown, but if there is a flow of interstellar material around it from a particular direction (an interstellar wind), the heliosphere may be like the Earth’s magnetosphere: spherical on one side, but drawn out into a long tail on the other. Data from the Voyager 1 spacecraft indicate that in 2012 August it exited the heliosphere and entered interplanetary space.