A theoretical companion star to our sun, nicknamed "Nemesis," may be responsible for hurling killer comets at Earth at regular intervals, potentially causing mass extinctions, including the one that wiped out the dinosaurs. UC Berkeley physicist Richard Muller proposes that this red dwarf star, orbiting a shared center of gravity with the sun, periodically passes through the Oort Cloud, a region of icy objects at the solar system's edge. This gravitational disturbance sends a barrage of comets towards Earth.
Muller estimates that the next such "barrage" could occur in approximately 12 million years. The theory is supported by research indicating extinction events on Earth occurring on a roughly 26-million-year cycle. One such event, 66 million years ago, is linked to the impact that led to the extinction of the dinosaurs.
Nemesis has remained elusive because it orbits the sun in lockstep, making its apparent movement across the sky minimal. Its dimness and position within the plane of the solar system, amidst countless other stars, further contribute to its hidden nature. The long-period comets ejected from the Oort Cloud could trigger catastrophic events lasting for millions of years.
While a 2014 study analyzing data from NASA's WISE infrared telescope found no evidence for such a star, Muller maintains that there is no definitive proof against his theory due to Nemesis's hidden status. The nature of the object that impacted Earth 66 million years ago, whether an asteroid or comet, remains a subject of debate among scientists.