Whose discovery showed that Pluto is not the only small world beyond Neptune?
Quick Answer
Eris was discovered by Michael E. Brown and colleagues in 2005. It helped redefine the Solar System and contributed to Pluto being classified as a dwarf planet.
The Full Story
The discovery of Eris in 2005 by Michael E. Brown, Chad Trujillo and David Rabinowitz showed that Pluto was not unique among large trans-Neptunian objects. Eris appeared slightly smaller than Pluto but similar enough to force astronomers to rethink what counts as a planet. The debate culminated in the International Astronomical Union’s 2006 definition of a planet, which reclassified Pluto as a dwarf planet. Eris remains one of the most important finds in modern planetary science.
Key Facts
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"The discovery that made Pluto lose its planet status"
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