Thoughty2 (Arran) is a British YouTuber and gatekeeper of useless facts. Thoughty2 creates mind-blowing factual videos about science, tech, history, opinion and just about everything else.
But the planet may not be a planet after all and the reason it has alluded astronomers for so long could be because it is in fact a primordial black hole - the name given to very old and relatively small black holes.
Although small, it would have a mass larger than the Earth and scientists believe it could actually be one of a population, meaning there could in fact be a whole swarm of black holes on the fringes of the solar system.