Did a 5th Giant Planet Mess up the Orbits of Jupiter, Saturn, Uranus and Neptune?

The solar system's current planetary position seems stable, but it is only because the planets have settled into them over billions of years.

The best model scientists have for the formation of the solar system is known as the Nice model, after the town in France, where it was first developed in 2005. The instability in the system caused those planets to go into a much more irregular and oblong pattern.

It has been a mystery as to what caused that anomaly. A group of researchers from Michigan State University, the University of Bordeaux, and the Zhejiang University think they have an answer.