Link: https://www.zmescience.com/science/news-science/astronomers-may-have-found-the-first-direct-hint-of-planet-nine/

Last time I remember reading about Planet X / Planet 9, it was hypothesized to exist so far out in Sol's orbital range that it was extremely difficult to spot via conventional telescope technology of all types. Moreso that it kept showing up in mathematical equations of the Solar system, necessary to balance out... I think it was certain orbital eccentricities of the outer gas giants and Mickey Mouse's pet dog, IIRC.

I always believed in you, Racer X Planet 9!

Planet 9 is and always has been Pluto

TBH, I'm pretty good at doing a good Mickey Mouse impression, as well as pissed off former-Pluto-fans. XD

If you're going to consider dwarf planets as planets, then Pluto would be the 10th planet from the sun that we know of so far because Ceres exists.

Does that make Eris, Haumea, Makemake, Charon, Quaoar, Sedna, Orcus, etc. planets 10, 11, 12, and so on?

And what about Ceres? It was considered a planet for about half a century... why give it to Pluto and not to Ceres, which has seniority..?

And Triton... it used to be a Kuiper belt object like Pluto, and is significantly larger... sure, it's currently orbiting Neptune, but if we disregard everything that makes Pluto not a planet we can also disregard that and call Triton a planet too, or an Opel Corsa, for that matter, or a (somewhat larger than average) small piece of lint, since we're completely ignoring any semblance of logic and common sense...

Pluto will always be interesting to scientists, planet or not. Planet status isn't a demotion of Pluto, it's more to clean up the fuzzy lines. The category of asteroids was created because too many were being classified as planets, and now we know there are THOUSANDS of asteroids. Even though they are no longer planets, asteroids are still super interesting for astronomers (incl. Ceres, the largest asteroid)!

Likewise goes for Pluto, it might have a subsurface ocean, and it's a bit weird that it's in a binary system with its "moon", Charon

The "planet" definition has been challenged again, as we have recently discovered a brown dwarf orbiting a star, itself with a Jupiter-like "exomoon" / "exosatellite" that is closer to the gas giants than the moons of the Solar System. This is the first "exomoon"/"exosatellite" discovered (because it's big!), but it has sparked yet another debate over what a planet or moon is.

If you didn't know, brown dwarfs are "failed stars" that have enough energy to fuse hydrogen into deuterium, but not enough to produce helium. Again, should this be considered an exoplanet as it orbits a star? Still being debated

Super exciting :D
Even if this isn't actually a planet and it's some other thing, it's still new phenomenon being learnt about the Solar System!