E.C. Tubb 
Coming Event 
The Dumarest Saga Book 26

The Terridae believed the lost Earth was heaven and utopia combined. In their artificial planet, they moved slowly through the universe in search of it. And in their eyes, the rediscovery of Earth was to be the Event.Now they said the Event was coming! Earl Dumarest — who was born on Earth and knew the truth — was an unwelcome visitor among them. If they knew of Earth’s whereabouts, they were not telling him.But another Event was already on its way. A Cyclan ship was rapidly approaching the Terridae’s world, confident that this time Dumarest would fall into their heartless clutches.Dumarest was not ready to flee — but if he stayed there would be no Earth for him, only a long, lingering doom.(First published 1982)