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.

Introduction

Our solar system is the best template for understanding the properties of extrasolar planetary systems. The interaction between the Sun and the constituents of its galactic environment regulates the properties of the interplanetary medium, including the influx of interstellar matter (ISM) and galactic cosmic rays (GCR) onto planetary atmospheres. In the case of the Earth, the evolution of advanced life occurred during the several million year time period when the Sun was immersed in the vacuum of the Local Bubble (Frisch & York 1986, Frisch 1993). Here we use our understanding of our heliosphere to investigate the astrospheres around extrasolar planetary systems.