The First Five Official Dwarf Planets
Four of the five dwarf planets reside in the cold region of the solar system beyond Neptune's orbit. Of these, Pluto was the only one to be demoted from full planet to dwarf planet, a decision that became official on August 24, 2006. Eris is slightly larger than Pluto, and farther away from the sun. Makemake is thought to be the third-largest dwarf planet (after Eris and Pluto). Haumea's claim to fame is its shape: it looks like an American football, and spins at a dizzying pace, completing a full rotation in under four hours. Finally, there's Ceres, the largest object in the asteroid belt. Its mass actually accounts for a full third of the belt's mass!
from SciShow Space
Key Facts In This Video
Currently, a planet is defined as a body that orbits the sun, has enough mass to be spherical, and has an orbital path all to itself. (0:27)
In 2015, astronomer Jean-Luc Margot proposed a new definition for planets that would encompass exoplanets found outside the solar system. (1:09)
V774104 is the farthest object ever detected in our solar system, and is thought to be a dwarf planet. (2:12)