The Olympium of Bacchus 12

The year is 2614 - 206 years after Earth was destroyed in a natural cataclysm and the United Earth Planets Confederation (UEPC) became humanity's new home. Spread across cluster of 8 star systems, the 22 inhabited planets of the UEPC thrived and were at peace for more than 200 years... until they came. In an unprovoked attack, alien invaders wipe out the UEPC's battle fleet and all major cities on 21 planets. Hidden between two great nebulas on the edge of UEPC space, only Bacchus 12 is spared from destruction. The population of Bacchus 12, along with the survivors rescued from the other UEPC planets, must work together to defend humanity and deny the aliens the prize that they desire most - the mineral Olympium, which exists on Bacchus 12.