Nicknamed Nemesis or The Death Star, this undetected object could be a red or brown dwarf star, or an even darker presence several times the mass of Jupiter... Our solar system is surrounded by a vast collection of icy bodies called the Oort Cloud. If our Sun were part of a binary system in which two gravitationally-bound stars orbit a common center of mass, this interaction could disturb the Oort Cloud on a periodic basis, sending comets whizzing towards us.