1997, Gerrit L. Verschuur, Impact!: The Threat of Comets and Asteroids, page 131
[p 130] The Death Star, which some called Nemesis, is supposed to be in a long-period orbit about [t]he sun. Every 20 million years it is believed to come close to the sun and pass through or near the Oort comet cloud. Comets are then likely to be propelled into new orbits into the inner solar system. When Nemesis is near, things become stirrud up so badly that the chance of earth being struck by a rogue comet is supposed to go way up.
[p 131] This hypothesis invokes the existence of planet X to disturb the Oort comet cloud from time to time, but it seems to be about as relevant as the Death Star idea.
