Interstellar material surrounding an extrasolar planetary system interacts
with the stellar wind to form the stellar astrosphere, and regulates the
properties of the interplanetary medium and cosmic ray fluxes throughout the
system. Advanced life and civilization developed on Earth during the time
interval when the Sun was immersed in the vacuum of the Local Bubble and the
heliosphere was large, and probably devoid of most anomalous and galactic
cosmic rays. The Sun entered an outflow of diffuse cloud material from the
Sco-Cen Association within the past several thousand years. By analogy with the
Sun and solar system, the Galactic environment of an extrasolar planetary
system must be a key component in understanding the distribution of systems
with stable interplanetary environments, and inner planets which are shielded
by stellar winds from interstellar matter (ISM), such as might be expected for
stable planetary climates.
