Ambassador by William Alexander

Gabe Fuentes is reading under the covers one summer night when he is interrupted by a creature who looks like a purple sock puppet. The sock puppet introduces himself as the Envoy and asks if Gabe wants to be Earth’s ambassador to the galaxy. What sane eleven-year-old could refuse?

Some ingenious tinkering with the washing machine sends Gabe’s “entangled” self out to the center of the galaxy. There he finds that Earth is in the path of a destructive alien force—and Gabe himself is the target of an assassination plot. Exactly who wants him out of the way? And why?