Almost twenty years ago, the discovery of the new object Eris, upset a lot of basic ideas about planets in our solar system. With hundreds of these objects of different colors now known, we are discovering details that define Pluto’s place in the solar system. Naming these new objects must follow specific IAU rules. We now have a number of three letter acronyms such as KBO, EKO, and SDO, which define different classes of these objects. Most recently, the I.A.U. has decided on the designation 'pluton' for that class of smaller objects similar to Pluto. However, there is still some confusion about the new terms. For over a decade now, several new objects have joined the growing club of dwarf planets. The largest of these objects, Eris, is in fact bigger than Pluto. We now know that at least one of these Kuiper objects has a ring system.
Carpe Caelum Planetary Astronomy