A planet is a planet is a planet


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I have wide and varied interests and opinions. Many of them would be considered arbitrary. I am often called a 'fountain of useless knowledge', or lately Wiki-Rob. Of course, this leads me to feel that most of the world suffers from a poverty of intellect on the grandest scale. People are literally starved of knowledge. One such subject, which will invariably mean bugger all to most people, is the conclusion of a rather long-standing and contentious debate about the definition of what constitutes a planet.

The International Astronomical Union (IAU) concluded (in 2006) two years of work defining the difference between "planets" and the smaller "solar system bodies" such as comets and asteroids. I have always held the opinion that Pluto had no right being called a planet and I used to prefer calling it a planetoid. This is for a number of reasons, greatest of which would be its orbit. It is highly tilted and rather eccentric with respect to the other 8 traditional planets (technically referred to as a large orbital inclination and eccentricity). It is neither terrestrial nor jovian (gas giants), but rather made of ice and rock, and its distance places it in the Kuiper Belt. I have always therefore contended that Pluto is actually a planetoid, the term given to large objects dwelling in the Kuiper Belt, an icy debris field of comet-like bodies extending billions of miles beyond the orbit of the distant planet Neptune.

However, the IAU has decided on a new term to distinguish these objects - Dwarf Planet. Which then places a relative sub-category within the definition of planet.

This problem arose simply because no one truly new the definition of a planet and what makes something a planet. It simply means 'wandered' in Greek and whenever a 'big thing' orbiting the sun was discovered by astronomers it became a planet.

The current official definition is: "IAU Resolution 5 for GA-XXVI" that states "A planet is a celestial body that (a) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and (b) is in orbit around a star, and is neither a star nor a satellite of a planet."

However... Charon, traditionally Pluto's moon has also now been included into the planet list.This is because the centre of gravity for Pluto and Charon is between them, not inside either one. So technically, Charon is not orbiting Pluto but is orbiting the centre of gravity of the two bodies, and just like that BAM a moon becomes a planet, even though our own moon and many others of say Saturn or Jupiter literally make Pluto look like a small fry.

It'll all take some getting used to, but I for one am glad that I no longer have to argue with dimwits about the subject. Arguing with anyone that Pluto was not in fact a planet has gotten me helluva worked up in the past and now finally I can claim to have been right (and wrong) all along. It is a planet according to the new definition, but falls more appropriately into the subcategory of dwarf planet. Although I don't see what was wrong with the term planetoid. At the same time planetoid is often confused with asteroid objects.

Pluto dodged a bullet and remains in the 'planet' category. Although, I still maintain that it exhibits far too many incongruencies when compared to the other eight for it to belong in the planet definition. So even though this new definition may bring some settlement to the argument, it seems it will not go to bed properly.

Nevertheless, we are looking further and further into our galaxy and learning more and more. I'm intensely interested, not only in the world around us, but in the worlds arounds us. Hopefully one day our species will be inhabiting those worlds.

Okay, you can wake up now.

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