The missing planet bumped into Neptune before disappearing into the abyss of space, according to a new study.
The four gas giant planets in our solar system -- Jupiter, Saturn, Uranus, and Neptune -- may have a long-lost relative. According to a new study, our system was once home to a fifth gas giant that suddenly vanished some 4 billion years ago after a run-in with Neptune.
Indirect evidence for this lost world is seen in a strange cluster of icy objects -- called the "kernel" -- in the Kuiper Belt. That's the vast region of primordial debris that encircles the sun beyond the orbit of Neptune.
"The Kuiper Belt is a perfect clue to understanding how the solar system evolved since its formation," study author Dr. David Nesvorny, an astronomer at the Southwest Research Institute in Boulder, Colo., told New Scientist.