Heaven's Reach — David Brin

The brutal enemy that has relentlessly pursued them for centuries has arrived. Now the fugitive settlers of Jijo both human and alien--brace for a final confrontation, The Jijoans' only hope is the Earthship Streaker, crewed by uplifted dolphins and commanded by an untested human. Yet more than just the fate of Jijo hangs in the balance. For Streaker carries a cargo of ancient artifacts that may unlock the secret of those who first brought intelligent life to the Galaxies. Many believe a dire prophecy has come to pass: an age of terrifying changes that could end Galactic civilization, As dozens of white dwarf stars stand ready to explode, the survival of sentient life in the universe rests on the most improbable dream of all--that age-old antagonists of different races can at last recognize the unity of all consciousness.