Planets, Dwarf Planets, and SSSBs!
How it all started...
Classifying Planets in the Past vs. Present
A new distinct class of objects called dwarf planets was also decided on. It was agreed that planets and dwarf planets are two distinct classes of objects.
Currently five objects accepted as dwarf planets: ceres, eris, Pluto, makemake, and haumea, previously known as 2003 UB313.
- Pluto is recognized as an important part of the Trans-Neptunian class.
Small Solar System Bodies (SSSBs)
Small solar system bodies (SSSB) include objects like: comets, asteroids, small planetary satellites, Triton, Pluto, Charon, and interplanetary dust.
SSSBs used to be called minor planets, but the name later changed.
The IAU classifies all objects orbiting the Sun that are too small to satisfy the definition of planet or dwarf planet as SSSBs.
Official Definitions of the IAU
Planet: a celestial body that orbits the Sun.
Classify: arrange in classes or categories according to stored qualities and characteristics.
Planets, dwarf planets, and SSSBs are all new definitions of the IAU.
When and why the views started changing...
How the IAU views the solar system changed in 1992 on August 30th. The view changed after the discovery by David Jewitt and Jane Luu from the University of Hawaii of the first of more than 1000 now known objects orbiting beyond Neptune in what is often referred to as the transneptunian region. The landscape of the solar system is always changing. Planets and dwarf planets are two distinct classes of objects.
More Information on Pluto
Nearly 80 years ago Clyde Tombaugh discovered Pluto.
He found Pluto by comparing 2 plates, showing a region in the constellation of Gemini.
As he switched back and forth between the 2 he spotted a small object.
The object he discovered was later named Pluto, a name officially adopted by the American Astronomical Society.