Galaxy's Edge — Douglas Hill

The Edge - the farthest solar system of the civilized galaxy. Its one inhabitable planet, Tallyra, is unconventional, ungovernable an teeming with crooks - and it's where young Jaxie Cade heads when he breaks jail with stolen information that could lead him to the fabled Phantom Planet, the dream of every Edge-worlder...

But trouble is right behind Cade: trouble from the alien Occians, from whom Cade stole the information; and from Raishe - a bounty-hunter and combat-ace determined to drag Cade back to prison. And that's before the Commonwealth Intelligence Agency turns up - or the evil, mysterious criminal, Acs, takes a hand...