Brown and Batygin are the point men for the current hypothetical unknown outer planet. Both do and have done presentations about the research, loads of them show up in YT vids. Batygin's in this one:
A planet has been predicted to orbit the sun with a period of 10,000 years, a mass 5x that of Earth on a highly elliptical and inclined orbit. What evidence supports the existence of such a strange object at the edge of our solar system?
Huge thanks to:
Prof. Konstantin Batygin, Caltech
Prof. David Jewitt, UCLA
I had heard about Planet 9 for a long time but I wondered what sort of evidence could support the bold claim: a planet at the very limits of our ability to detect one, so far out that its period is over 60 times that of Neptune. The planet 9 hypothesis helps explain clustering of orbits of distant Kuiper belt objects. It also explains how some of these objects have highly inclined orbits - up to 90 degrees relative to the plane of the solar system. Some are orbiting in reverse. Plus their orbits are removed from the orbit of Neptune, the logical option for a body that could have ejected them out so far. The fact that the perihelion is so far out suggests another source of gravity was essential for their peculiar orbits.Does Planet 9 Exist? | September 13, 2019 | Veritasium
It’s interesting that Dr. Batygin in his brief recap of history did not even mention John Couch Adams, usually given at least equal credit for the prediction of Neptune along with LeVerrier (and in English-language sources maybe slightly more even though it was LeVerrier’s prediction that led directly to the actual discovery). Such was the situation back when I was teaching (I retired in 2014); since then I haven’t kept up, but I see that Wikipedia still gives Adams some credit. The complete story of Neptune’s discovery is a rather interesting study in the sociology of science. However, that would be too great a digression from the subject of the video.