Did you hear that an actual other planet that has never been confirmed. Here is a bit more about it:
A possible planet – larger than Earth but smaller than Neptune – orbiting the Sun once every 15,000 years, could explain the peculiar clumping of Kuiper Belt Objects in our solar system. Astronomers Konstantin Batygin and Mike Brown of the California Institute of Technology (Caltech) describe how large telescopes could detect this world, if it exists.
Now in terms of the search they have narrowed the area by 50%:
A team of French scientists have put forward the conclusion, based on data from the Cassini spacecraft, that two very large zones from the search area can be excluded. These two zones make up for about fifty per cent of the total search space thereby reducing the search area where future research may concentrate.
Here is the wikipedia page on it BEFORE this discovery from Caltech:
Following the discovery of the planet Neptune in 1846, there was considerable speculation that another planet might exist beyond its orbit. The search began in the mid-19th century and culminated at the start of the 20th with Percival Lowell‘s quest for Planet X.
Let’s watch videos of the simulation of “planet” x on the next page