Fleet Of Worlds

Humanity has been faithfully serving the Citizens for years, and Kirsten Quinn-Kovacks is among the best and the brightest of the humans. She gratefully serves the race that rescued her ancestors from a dying starship, gave them a home world, and nurtures them still. If only the Citizens knew where Kirsten's people came from.
A chain reaction of supernovae at the galaxy's core unleashes a wave of lethal radiation that will sterilize the galaxy. The Citizens flee, taking their planets, the Fleet of Worlds, with them.