Nemesis

A red dwarf star called Nemesis is moving through space on a path toward Earth. Its approach threatens the planet with destruction, and the book opens on that danger.

Rotor, a colony founded from Earth, circles Nemesis. Its inhabitants have deliberately cut themselves off from an Earth they regard as anarchic, degenerate and worn out, and they have built a utopian society of their own. For them Rotor works as a kind of Ark. It also carries hidden dangers that have to be understood.

The novel is science fiction set in the twenty-third century. It is a work of Isaac Asimov's late career, written two years before his death, and it belongs to his unified future history, which joins his Robot stories to the Empire series. The action falls shortly before the discovery that makes true faster-than-light travel possible.

The tension rests on two threats: a star closing in on Earth, and the unexamined risks inside a colony that believes it has found safety.