Eris: The Dwarf Planet That Declassified Pluto

In January 2005, the dwarf planet Eris was discovered by Michael Brown. At the time, it was thought to be bigger than Pluto by 500 km.

The discovery raised many questions, one of the most important ones being: should Eris be added as the next planet after Pluto? Scientists had to make a tough choice, as the discovery of Eris opened up the possibility of the existence of other large objects of similar size in the outer solar system.

On what factors would they make the choice? This is the story of how the discovery of Eris led to the declassification of Pluto as a planet.