Spindrift — Allen Steele

June 1, 2288 -- Europe's first starship, the EASS Galileo, launches on its maiden voyage to venture into unexplored space. Its classified mission: investigate an unidentified, possibly alien object traveling outside our solar system, code-named Spindrift. Soon after taking off, the Galileo disappears...

February 1, 2344 -- A shuttle from the Galileo returns to Earth carrying three surviving expedition members. The Galileo has been destroyed, and the rest of the crew is lost -- but the survivors have not aged. For they have indeed made contact with an extraterrestrial race -- and become enmeshed in a conflict that brought them face-to-face with the most apocalyptic force in the galaxy...