In the outer solar system, beyond all the planets, there’s a lot of stuff. Small rocky and icy objects orbit the sun at enormous distances. But strangely there’s a group of these objects that seem to be clustered together. Now, the use of the word 'clustered' might imply that these objects are close together. But they are not. Not even a bit. It's just that they are on similar (and somewhat confusing) orbits. The question is, what could possibly have caused them all to orbit this way? That’s a rhetorical question – but it’s gravity of course, and in this case, maybe the gravitational influence of a nearby planet. Maybe one that is so far away we can’t even see it. Maybe one called Planet Nine (trademark pending).
Apologies here to Pluto, who used to be the ninth planet in our solar system until it was demoted to a dwarf planet and so doesn't count for the purposes of tallying up planetary status anymore. Anyway astronomers have been looking for Planet Nine since around 2014. They’ve done the calculations, and they think they know where it is. But looking for a distant spec of light against a backdrop of billions of stars is not exactly easy. Thankfully, technology has improved over the years, and we have data going back decades that we can extract more information from than ever. So now a team in Taiwan think they have found it. They used data from 1983 and compared it to data from 2006 and found a spec of light that seems to have moved just about the right distance. But before we all get too excited, there is a problem. The orbit of the spec of light (or potential new planet) is much different to the orbit that Planet Nine was expected to have. And there’s no way the original Planet Nine could exist if this new find is also a planet because the gravitational effects they’d have on each other would make their orbits unstable.
So, if the new Planet Nine does turn out to be a planet, it actually disproves Planet Nine – which is what they were trying to prove. There's a fun bit of irony. The original proposers of Planet Nine are calling the new maybe-a-planet Planet 8.5. Anyway, the good news is that the Vera C Rubin Observatory comes online later this year, and it should be able to detect the actual Planet Nine if it really exists.
But it is funny to think that a planet about 4 times bigger than earth could be lurking on the outskirts of our solar system and we haven’t even seen it yet, despite the fact our telescopes can look so far they can see back to the birth of the universe.
