In 2012 Karens and tinfoil hat wearing people in need of feeling significant thought that the world would end by a rogue planet, Nibiru, or, if you are creatively bankrupt, Planet X, would collide with Earth. Unfortunately that didn't happen. However, asteroids such as Pluto are affected by an invisible mass as heavy as Neptune. There is no 9th planet but the gravitational pull is real - the only explanation left is that this object, named Nibiru (not the same one as the made-up Karen Niburu) is a baseball sized black hole! Something like that would be almost impossible to detect and you'll need to do it by disproving the other options just as happened here.
Maybe you could use a hilariously tiny version of your black hole dragon now?
Recently stumbled upon your art while browsing planets 'n the like, and I must say I'm a fan of your planet dragons. I like their designs! Do you have ideas to make any more characters, like Eris or Vulcan?