Yanked - David Brin

Teens from across time are pulled into the twenty-fourth century for an interstellar rescue mission in this action-packed science fiction series debut.
Life is easier in the year 2345, since humanity has created a utopia with no more war, disease, or crime. Only now, Earth is in a dire situation, one which the adults are powerless to help. A group of teenagers step up to the challenge, but they'll need help. . . . Enter Operation Hourglass . . .
A team of heroes—champions of their times, spanning history—is assembled, each of them known to have the skills, grit, and instincts to handle crisis. From the twentieth and twenty-first-centuries: a high-school basketball star and a smalltown brainiac. Joining them: a tenth-century Viking and a young thief from nineteenth-century London. Together they must rescue a human star settlement from mysterious, threatening, three-eyed aliens.
But even if they survive and successfully complete their mission, there's still the matter of returning everyone back to their pasts . . .