Pluto in size of Charon and Pluto has prompted some astronomers to call it a double dwarf planet. The system is also unusual among planetary systems in that each is tidally locked to the other, which means that Pluto and Charon always have the same hemisphere facing each other. From any position on either body, the other is always at the same position in the sky, or always obscured. This also means that the rotation period of each is equal to the time it takes the entire system to rotate around its barycenter. In 2007, observations by the Gemini Observatory of
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