Michael Brown

Mike Brown and his team at Caltech discovered several major trans-Neptunian objects in addition to Eris, including Sedna (2003), Haumea (2004, disputed with a Spanish team), and Makemake (2005). Makemake and Haumea were subsequently classified as dwarf planets alongside Pluto and Eris. Brown's discoveries fundamentally reshaped the understanding of the Kuiper Belt and the outer solar system.

Mike Brown is nicknamed 'Pluto Killer' because his 2005 discovery of Eris, which was initially thought to be larger than Pluto, forced the International Astronomical Union to formally define what constitutes a planet. This process led to Pluto's reclassification as a dwarf planet in August 2006. Brown embraces the nickname and titled his 2010 memoir 'How I Killed Pluto and Why It Had It Coming.'

Mike Brown and Caltech colleague Konstantin Batygin published a paper in 2016 proposing the existence of Planet Nine based on the clustering of orbits of several distant Kuiper Belt objects. The hypothesis suggests a planet roughly 5-10 times Earth's mass orbits far beyond Neptune, gravitationally shepherding these objects into aligned orbits. As of the mid-2020s, Planet Nine has not been directly observed despite ongoing telescope surveys.

Mike Brown authored 'How I Killed Pluto and Why It Had It Coming,' published in 2010. The book recounts the discoveries of Eris and other distant objects and provides a personal account of the scientific process that led to Pluto's 2006 reclassification. It also details Brown's controversy with a Spanish astronomer over the discovery of Haumea.