Scientists propose Pluto and its moon Charon formed through a "kiss and capture" event 4.5 billion years ago, challenging previous theories about their unique size ratio and orbital relationship.

“Because Pluto is rotating rapidly prior to the collision, and because Charon lies mostly outside of their corotation zone, it is able to ‘push’ Charon off, and Charon starts to slowly migrate out,” first author Dr. Adeene Denton, a planetary scientist from the University of Arizona, told The Guardian.