The astronomers, Konstantin Batygin and Mike Brown who recently announced their findings never claimed that they found a 9th planet. Instead, they suggested that a large body with 10x earth mass would explain the perturbations in the orbits of other objects in the inner Oort cloud.
Bottom line: a planet has NOT been found; only evidence that such a planet may exist. At this stage it is a hypothesis, and much data gathering and observation are needed to test the hypothesis.
Most of what one reads on the internet and in the media must be passed through a bullshit filter. The media are known for twisting facts. Very few journalists have the science background necessary for accurately reporting scientific findings.
So, where does one find reliable information? Here is one source which may be trusted: Scientific American. However, the scientific journals in which such findings are usually published, are the most reliable sources of all. In the case of the possible 9th planet, the journal is The Astronomical Journal in which Batygin and Brown published their findings under the title “EVIDENCE FOR A DISTANT GIANT PLANET IN THE SOLAR SYSTEM”.