Natural satellite been directly observed, have been called "moonlets". Small asteroid moons (natural satellites of asteroids), such as Dactyl, have also been called moonlets. The upper limit is also vague. Two orbiting bodies are sometimes described as a double planet rather than primary and satellite. Asteroids such as 90 Antiope are considered double asteroids, but they have not forced a clear definition of what constitutes a moon. Some authors consider the Pluto–Charon system to be a double (dwarf) planet. The most common dividing line on what is considered a moon rests upon whether the barycentre is below the surface of the larger
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