Orbital patterns of the two singularities produced an enormously destructive effect through space like a propeller through water. Over time the gravimetric disruptions had churned thousands of stellar objects, including a trio of neutron stars in the year 2267. Its core area was four light-years across. Hard radiation was lethal six light-years away. The fabric of spacetime was dramatically curved even from a distance of ten light-years, with time dilation and other effects reaching as far away as 17 light years.
In 2267, the Earth colony generational ship Wanderer was 17 light-years away from Polo's Bolos, and its fusion engines needed to be fired immediately for a course-correction to avert disaster. The USS Enterprise mounted a rescue mission. (TOS novel: The Galactic Whirlpool)