Our “neighborhood” in the Milky Way lies just inside one of the galaxy’s great spiral arms, the Orion Arm. The majority of the brightest stars are distributed along a section of sky known as Gould’s Belt (dashed ellipse), which also marks the distribution of the nearby star-forming regions in the Orion spiral arm. Stellar winds from these star-forming regions—such as the Scorpius-Centaurus association—push “shells” of interstellar material into the sun’s path.
The sun is currently on the edge of such a shell (not visible at this scale). The actions of interstellar winds and the sun’s own motion through the galaxy may alter the sun’s local galactic environment on time scales as brief as a few thousand years. The author discusses what space scientists know about the interaction between the solar system and its changing galactic environment.
(Adapted from the Oct. 1999 issue of National Geographic)