Nemesis (Theoretical)
From Multiversal Omnipedia
In the astronomical theories of Richard Muller, Nemesis is a theoretical companion star or brown dwarf with an orbit that takes it outside the Oort Cloud. According to Muller, its orbit would disrupt the orbit of comets in the Cloud, sending them towards Earth to hit every 26 million years. Nemesis would thus explain what some call a regular cycle of mass extinctions on Earth.
