The People of Novus had discovered that their home planet was about to be destroyed by a series of natural disasters, caused by a rogue black hole approaching the planet. Knowing this, they began to evacuate the people on the planet to several off-world colonies found earlier. Unfortunately, the planet's Stargate was lost in a lava flow and prevented the evacuation of the remaining people.
As a solution, they built several Evacuation Ships capable of carrying a large amount of passengers and cargo at a time. In addition, these ships have the ability to fly for hundreds of years while sustaining multiple generations of people. The ships set a course to their nearest colony, but the journey there would take at least two hundred years since the ships did not have hyperdrives and were not FTL-capable. (SGU: "Epilogue")