ABSTRACT
Astrophysical hazards originating beyond the Solar System, including gamma-ray bursts and nearby supernovae, subjectively pose a negligible risk to contemporary human civilization, but may have severely impacted the terrestrial environment over the course of billions of years. This chapter offers a broad review of the threats posed by these and other galactic hazards, including a possible flare up in the supermassive black hole at our Galactic Center, Sgr A*. It also assesses the influence of such hazards on the habitability of life-bearing planets in our Galaxy and others across cosmic time. With the explosion in the number of known planets around other stars in recent decades, and the prospect that some of them may harbour soon-to-be detectable life, it reviews the risks and challenges surrounding our search for life beyond Earth, specifically of the intelligent variety.
