Planets, Dwarf Planets, and SSSBs!

Oh My!

How it all started...

The IAU (International Astronomical Union) was founded in 1919. It currently holds 11,447 members, and has a total of 96 countries participating in research. The mission of the IAU is to promote and safeguard the science of astronomy in all the aspects through international cooperation.
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Classifying Planets in the Past vs. Present

In the past the IAU classified all planets by color, elements like: air, fire, earth, and water, surface texture was looked at, and also Nebula around it. Nowadays how they classify planets is more detailed and complicated. They look at five different classifications. They look at things like interior planets which is inside the Earth's orbit. They also look at superior planets which means it is outside of Earth's orbit. They look at the inner and outer planets meaning it is inside the asteroid belt, and outside the asteroid belt. And they also look to see if it classifies as a gas giant (like Jupiter).

Dwarf Planets

  • 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.