Portion of the Galaxy where an event with energy E is lethal for a planet at R (solid black circle). The hazard distance d identifies the circular region within which a GRB of energy E ≥ 4πd²F_c can produce a lethal fluence. q represents the galactocentric distance of the GRB. In this sketch the center of the polar coordinate system (identified by the arrow R) is the location of the planet.