Beyond Pluto

Sf readers soon learn the difference between interplanetary and interstellar space but there are intermediate layers.

In "The Snows of Ganymede," when Hall Davenant is Coordinator of the Order of Planetary Engineers, men are on Pluto and the next stop is thought to be the stars. Not necessarily. Between Pluto and Proxima Centauri, there are:

hypothetical trans-Plutonian planets;
the Kuiper Belt;
the Oort Cloud;
presumably similar regions around Proxima.

See Cosmography.

Given a source of energy, there would be plenty to explore out there and maybe to colonize as in Poul Anderson's Harvest Of Stars Tetralogy.