Humankind headed out to the stars not for conquest, nor exploration, nor even for curiosity. Humans went to the stars in a desperate crusade to save intelligent life wherever they found it. A wave of death is spreading through the Milky Way galaxy, an expanding sphere of lethal gamma radiation that erupted from the galaxy's core twenty-eight thousand years ago and now is approaching Earth's vicinity at the speed of light. Every world it touched was wiped clean of all life. But it's possible to protect a planet from gamma radiation. Earth is safe.
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