The 4% Universe: Dark Matter, Dark Energy, and the Race to Discover the Rest of Reality

by Richard Panek

1980, Luis Alvarez, along with his son Walter Alvarez, had hypothesized that the mass extinction of the dinosaurs 65 million years ago, at the cusp of the Cretaceous and Tertiary periods, had been caused by a comet or asteroid impact that had disrupted the global ecosystem. Then, in 1983, a pair of paleontologists announced that they had discovered evidence of a cycle of mass species extinctions every 26 million years. The following year, Muller and some colleagues published a paper speculating on the existence of a companion star to the Sun—Nemesis. Every 26 million years, they wrote, the highly elliptical orbit of Nemesis would bring it relatively near the Sun, and its gravitational influence would draw comets from the farthest reaches of the solar system into the orbital paths of the planets nearest the Sun, including Earth. The idea wasn’t as fanciful as it might seem; studies of Sun-like stars had shown that about 84 percent were in binary systems, meaning that the Sun, if solo, would be an anomaly. Muller assigned Perlmutter the task of looking for Nemesis (or the Death Star, as the media called it), and in 1986 Perlmutter completed his thesis, “An Astrometric Search for a Stellar Companion to the Sun.”