nemesis theory

Theory of animal extinction, suggesting that a companion star to the Sun caused the extinction of the dinosaurs and other groups of animals.

The theory holds that the movement of this as yet undiscovered star disrupts the Oort cloud of comets every 26 million years, resulting in the Earth suffering an increased bombardment from comets at these times. The theory was proposed in 1984 to explain the newly discovered layer of iridium – an element found in comets and meteorites – in rocks dating from the end of dinosaur times. However, many palaeontologists deny any evidence for a 26-million-year cycle of extinctions.