Plutoid: Plutoids are celestial bodies in orbit around the Sun at a distance greaterSo Pluto is no longer a planet, ruining all that time I spent on the toilet in 7th grade reading "The Search for Planet X" by Clyde Tombaugh. (I have no idea why, but that is my association with the book.)
than that of Neptune that have sufficient mass for their self-gravity to
overcome rigid body forces so that they assume a hydrostatic equilibrium
(near-spherical) shape, and that have not cleared the neighbourhood around
their orbit. The two known and named plutoids are Pluto and Eris. It is
expected that more plutoids will be named as science progresses
and new discoveries are made.
The International Astronomical Union also says:
The dwarf planet Ceres is not a plutoid as it is located in the asteroid belt between Mars and Jupiter. Current scientific knowledge lends credence to the belief that Ceres is the only object of its kind. Therefore, a separate category of Ceres-like dwarf planets will not be proposed at this time.This is getting a little confusing, and frankly right now I don't know what to tell my 3-yr old nephew, who is starting to learn about dinosaurs and planets. How many planets are there (8?), and how many plutoids (2?), and what the heck is Ceres?