Some of our planets deviate slightly from the elliptical orbit that is calculated standard path. There are a few astrophysicists who believe or at least suspect that there is another planet out there, somewhere within or more likely beyond the Kuyper belt. That planet, if it is there, would account for the anomolies in the orbits. The planet has no name so it is being called Planet Nine. 3.7 times more massive than Earth and has an orbit that is on average about twenty times as far from the sun as Neptune Neptune has an orbit time of 165 years but planet Nine will need 15,000 years.
Bluenose is surely right that we may be on the cusp of discovering new things just like those old guys in the 16th,17th, 18th, 19th centuries.....Newton, Brahe, Maxwell, Hooke, LeVerrier, Adams, Herschel, Hertz and all the rest. The power of Newtons law of gravity to predict what we cannot see - to make a map of the invisible world- has continued to reap dividends.