Phoenix - Cygnus 5: Book Three - Cygnus Five, #3

Once a penal colony of the Galaxy's most hardened criminals, Cygnus 5 is now home to the hopeful, the lost, the rejects and the rebels of a system that have left them to die. In a battle for the colony's survival, Aurora Campos-its defacto queen-awoke a doomsday machine left behind by the aliens who inhabited the world before her. Now the whole galaxy is at risk. Aurora and her band of misfits must prevent the entire human race from being turned into dust.
She must save her people from starvation, rescue her kidnapped daughter and argue a planet into submission. The way her life has been going recently, it's starting to look like a typical Monday.