You’re a Plutoid
After two years of what must have been grueling discussion, the International Astronomical Union has decided that things that are like Pluto (which used to be defined as a planet) are now going to be called “Plutoids” as long as they orbit at or beyond the orbit of Neptune. Dwarf planets (as a small-body definition), as you may recall, was an outcome of the 2006 IAU meeting, when it was decided that we needed a new category for worlds that aren’t quite planets, but are bigger than asteroids. The name plutoid for a specific subset of dwarf planets was proposed by the members of the IAU Committee on Small Body Nomenclature (CSBN), accepted by the Board of Division III, by the IAU Working Group for Planetary System Nomenclature (WGPSN) and approved by the IAU Executive Committee at its recent meeting in Oslo, Norway.
Two Plutoids: Pluto (shown with its companion Charon) and Eris (with Dysnomia)
So, what are the characteristics of Plutoids? They have to be celestial bodies in orbit around the Sun at a distance greater than that of Neptune. They must have sufficient mass for their self-gravity to overcome rigid body forces so that they assume a hydrostatic equilibrium (near-spherical) shape. And, they haven’t cleared the neighborhood (of debris) around their orbit. So, Pluto and Eris fit this definition, and scientists expect more small worlds like them to be found as astronomers keep finding them out the great beyond.
By this definition, the dwarf planet Ceres is NOT a Plutoid, but it’s still a dwarf planet. This is because its orbit is within the asteroid belt and not transneptunian.
I need the guys working on the dirt experiments on the Mars Phoenix Lander to help me with my floor-cleaning methods. I was doing some tidying up in my overstuffed office the other day. It’s something I do when I’m stuck in the middle of writing something and a case of temporary brain freeze hits. Usually I take a break and go get a coffee or something, but it’s too hot for coffee these days. So, sometimes I’ll do a little rearranging of the stuff in my office.