You would be forgiven if you have never heard of this object before, even if it is the third biggest dwarf planet in our solar system, third only to Pluto and Eris.
When Eris was discovered in 2005, it was briefly hailed as a tenth planet, but it sparked a debate in the astronomical community about what makes a planet a planet.
The real nail in the coffin came (thunder cracks) on the 5th of January, 2005, when astronomers discovered Eris, (gentle music) an object in the Kuiper belt that's around 30% more massive than Pluto.