Nemesis

Nemesis is a hypothetical celestial object—possibly a star or companion body—that some scientists theorize periodically disturbs the Oort Cloud, the distant region of icy bodies surrounding our solar system. This disturbance could send comets streaming toward Earth, potentially causing periodic mass extinctions and climate changes over millions of years. The idea of Nemesis aims to explain patterns of extinction events, but it remains speculative, with no direct evidence confirming its existence. It is a concept used in scientific discussions about the history and future risks associated with comet impacts.