Boundary between the heliosphere—the teardrop-shaped region around the Sun created by the solar wind and filled with solar magnetic fields and outward-moving gas—and the zone of transition to the interstellar medium. Its tail is estimated to reach 110–170 astronomical units from the Sun, encompassing the orbits of all the major planets. Its shape changes, influenced by a wind of interstellar gas produced by the Sun's motion through it.

This entry comes from Encyclopædia Britannica Concise.
For the full entry on heliopause, visit Britannica.com.

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