Astronomers discover dwarf planet Eris, sparking Pluto debate | This Day in Space (5 Jan. 2005)

On January 5, 2005, the Palomar Observatory-based team led by Mike Brown discovered a large world, later known as Eris, after systematically scanning for large outer Solar System bodies for several years. Unfortunately for Pluto, this was the beginning of the end for its official planet title.

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