Arguments for and against the existence of Planet X, and its possible size and location, continue even with the most modern measurements.
There has so far been no conclusive evidence for its reality, all previous theories having been explainable by measurement errors.
The major one of these was the determination of an error in earlier measurements of the mass of Uranus. Once a more exact figure for this was known, earlier pointers to Planet X were shown to be false.
So Planet X is still hypothetical. Many calculated possibilities for its mass and orbit have been made, but no observations. .
Answers & Comments
Arguments for and against the existence of Planet X, and its possible size and location, continue even with the most modern measurements.
There has so far been no conclusive evidence for its reality, all previous theories having been explainable by measurement errors.
The major one of these was the determination of an error in earlier measurements of the mass of Uranus. Once a more exact figure for this was known, earlier pointers to Planet X were shown to be false.
So Planet X is still hypothetical. Many calculated possibilities for its mass and orbit have been made, but no observations. .