The Fleet of Worlds

The Fleet of Worlds is the five (at one point six, as detailed in Fleet of Worlds) planets that are home to the Puppeteers, presently being moved in formation at sub-light speeds out of the galaxy to avoid destruction as the wave of radiation from an explosion of the galactic core sweeps towards the outer reaches of the galaxy. They orbit about each other in a Klemperer rosette. The central planet of the group is Hearth.

Sources and references: Neutron Star, A Relic of the Empire, The Color of Sunfire, Flatlander, The Soft Weapon, Ringworld, Fleet of Worlds,