Really like these mate and I also think the Explore, Expand and Explote would be a good edition for the trilogy 
cheers
James
Explore, Expand, Exploit - that's the one.
A star system with a dying sun in the last throws of existence. The habitation zone shrinks as another planet is plunged into a world of ice. The remaining population who haven't left the system on board colony relocation ships move between the various planets, moons and space stations or jealously guard them.
OR (to play on the meanings of the three Es)
A system with a young yellow dwarf has been discovered. Several planets are cold but habitable and others will be in a few thousand years. It is, however the mineral riches these planets and moons may hold that has brought companies, colonists and planetary alliances from all over the spiral to these new worlds. Outposts and space stations are built, laying claim over great swathes of world's and entire moons. But as these frozen world's that, something else is stirring.