When astronomers found a large world farther out than Pluto, it became one of the final nails in the coffin of our ninth ...

The discovery of the 2012 VP113 object lent weight to the Sedna hypothesis because Sedna and 2012 VP113 had similar orbits. As Brown puts it, he and his colleague proposed the Planet Nine ...

Sedna has been cited as possible evidence for ... nine planets—which it had before Pluto’s demotion in 2006—the discovery of a distant Earth-mass planet would have profound implications ...

Alongside, Sedna, Quaoar, and Eris, there was also the discovery of Makemake and Haumea, which called for a better way to classify planets. There were multiple proposals on how to change it ...