Computer analysis of the orbits of Uranus and Neptune gives some “best bets” for the distance and mass of possible planets, some predictions indicate a planet up to five times the mass of the Earth, several times as far from the Sun as Neptune, and possibly in a tilt orbit.
The existence of Charon was not suspected until 1978, when a small bump was noticed on Pluto’s image on a photographic. From 1985 to 1990, Charon’s orbit was positioned so that the satellite passed repeatedly in front of and behind Pluto. This revealed a great deal about both bodies. They both revolve about their common centre of gravity, a point in space between them. Likewise there is definitely more chances for another planet in the Solar System.