IAU definition of planet who had theorized on the existence of the large trans-Neptunian object Planet X, and Tombaugh been searching for Planet X when he found Pluto. Almost immediately after its discovery, however, astronomers questioned whether Pluto could be Planet X. Willy Ley wrote a column in 1956 titled "The Demotion of Pluto", stating that it "simply failed to live up to the advance publicity it received as 'Planet X' before its discovery. It has been a disappointment all along, for it did not turn out to be what one could reasonably have expected". In 1978, Pluto's moon Charon was discovered. By measuring
How I Killed Pluto and Why It Had It Coming How I Killed Pluto and Why It Had It Coming How I Killed Pluto and Why It Had It Coming is the 2010 memoir by Mike Brown, the American astronomer most responsible for the reclassification of the former planet Pluto from planet to dwarf planet. The memoir is an account of the events surrounding the redefinition of the term "planet" that eventually changed the status of Pluto. It chronicles the discovery of Eris, a dwarf planet then mistakenly thought to be larger than Pluto, located within the scattered disc, beyond Neptune's orbit. The replaying of events includes the adversarial challenging