Our Solar System

Farthest Regions

The point at which the Solar System ends and interstellar space begins is not precisely defined, since its outer boundaries are shaped by two separate forces: the solar wind and the Sun's gravity. The outer limit of the solar wind's influence is roughly four times Pluto's distance from the Sun; this heliopause is considered the beginning of the interstellar medium. However, the Sun's Roche sphere, the effective range of its gravitational dominance, is believed to extend up to a thousand times farther.

Heliopause

NASA image of the heliosheath and heliopause

The heliosphere is divided into two separate regions. The solar wind travels at roughly 400 km/s until it collides with the interstellar wind; the flow of plasma in the interstellar