Nemesis

In 1984, paleontologists David Raup and Jack Sepkoski posited that mass extinction events are cyclical, happening about every 26 million years, and are often caused by large impact events—such as the asteroid that may have led to the end of the dinosaurs 65 million years ago. Some astronomers sought to explain the theory with Nemesis, a hypothetical companion star to the Sun about 1.5 light-years away. According to the hypothesis, how was Nemesis responsible for these extinction events? More...