Right now I'm reading Dr. Mike Brown's book How I Killed Pluto And Why It Had It Coming. Only a couple of pages in, but so far it's been an interesting read.
Basically, he had discovered a new possible planet (Eris, aka Xena), and his discovery led scientists to finally formally define a planet for the first time. The new definition re-categorized Pluto and Eris as dwarf planets. Humbly, Dr. Brown was satisfied with that conclusion.
irbinator OP t1_j3kfgei wrote
Reply to comment by GetsGold in TIL Pluto hasn't completed an orbit around the sun since its discovery. Pluto's orbit takes about 248 years, and Pluto was discovered in 1930. by irbinator
Ah, you’re completely right. Thanks! I always mix up Ceres and Eris. I’ll update my comment now.