The claim has been made that the 9th planet is a black hole. I say it isn't. Neptune is our 9th planet. In order the first nine planets in our Solar System are...
Planets 10 and 11, Pluto and Charon, share an orbit and in effect switch between being #10 and #11 depending on where they are in their orbit around a common center of gravity. Our declaring the small planets to be "dwarf planets" is our attempt to deny that there really are too many planets for us to memorize them all, or devise a mnemonic to handle them.