The Great Implosion
In the usual scenario, human beings will settle the Galaxy by going “out there.” (sometimes known as The Great Explosion). This has the disadvantage that, if there is no method of FTL travel, the resulting colonies will be almost isolated from each other.
What if, instead of a Great Explosion, there's a Great Implosion, in which the planets are moved to the solar system? The stars can stay where they are provided they're surrounded by solar-power collectors and the resulting energy beamed toward the solar system. (It might be necessary to move them closer to do that right.)
I'm surprised that Isaac Asimov, with his well-known distaste for travel, didn't write about such a system.