This week I’ll be quickly reviewing dwarf planets. Probably the first image that pops into your head when I say that phrase is Pluto. Pluto is, after 2006, classified as a dwarf planet. In 2006, the International Astronomical Union (IAU), had a discussion about the definition of “planet”. Out of this discussion came a new term, “dwarf planet” and the knowledge that Pluto was not actually one of the big guys. However, the IAU was thoughtful to those of us who cherish Pluto and have decided to name the dwarf planets that orbit the sun beyond Neptune’s orbit as “plutoids”. That is a bit of consolation.
Dwarf planets are much smaller than the eight planets in our solar system. They still must be round but unlike planets, they are unable to clear their orbital paths. Dwarf planets are not moons, although some have their own. They are rocky and/or icy, depending on how close to the sun they are. Like the eight planets, dwarf planets do orbit the sun. The majority of them are found in the Kuiper Belt, a region of space beyond the orbit of Neptune. However, one dwarf planet, Ceres, is in the asteroid belt. As of now, the IAU and NASA recognize five dwarf planets: Ceres, Pluto, Eris, Makemake and Haumea. It is thought that there are many more waiting to be discovered and/or recognized.
Eris is the largest known dwarf planet.
So although it may break my heart that Pluto is no longer called a planet, I’m glad it still has a place in our solar system. I got this information from NASA’s Solar System Exploration site and Mike Brown’s Dwarf Planet article.