RESOLUTIONS
Resolution 5A is the principal definition for the IAU usage of "planet" and related terms. Resolution 5B adds the word "classical" to the collective name of the eight planets Mercury through Neptune.
Resolution 6A creates for IAU usage a new class of objects, for which Pluto is the prototype. Resolution 6B introduces the name "plutonian objects" for this class. The Merriam-Webster dictionary defines "plutonian" as:
Main Entry: plu • to • ni • an
Pronunciation: plü-'tO-nE-&n
Function: adjective
Usage: often capitalized
: of, relating to, or characteristic of Pluto or the lower world
After having received inputs from many sides -- especially the geological community -- the term "Pluton" is no longer being considered.
IAU Resolution: Definition of a Planet in the Solar System
Contemporary observations are changing our understanding of planetary systems, and it is important that our nomenclature for objects reflect our current understanding. This applies, in particular, to the designation 'planets'. The word 'planet' originally described 'wanderers' that were known only as moving lights in the sky. Recent discoveries lead us to create a new definition, which we can make using currently available scientific information.
RESOLUTION 5A
The IAU therefore resolves that planets and other bodies in our Solar System be defined into three distinct categories in the following way:
(1) A planet(I) is a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and (c) has cleared the neighbourhood around its orbit.
(2) A dwarf planet is a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape(II), (c) has not cleared the neighbourhood around its orbit, and (d) is not a satellite.
(3) All other objects(III) orbiting the Sun shall be referred to collectively as "Small Solar System Bodies".
(I) The eight planets are: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune.
(II) An IAU process will be established to assign borderline objects into either dwarf planet and other categories.
(III) These currently include most of the Solar System asteroids, most Trans-Neptunian Objects (TNOs), comets, and other small bodies.
RESOLUTION 5B
Insert the word "classical" before the word "planet" in Resolution 5A, Section (1), and footnote 1. Thus reading:
(1) A classical planet1 is a celestial body . . .
and
(I) The eight classical planets are: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune.
IAU Resolution: Pluto
RESOLUTION 6A
The IAU further resolves:
Pluto is a dwarf planet by the above definition and is recognized as the prototype of a new category of trans-Neptunian objects.
RESOLUTION 6B
The following sentence is added to Resolution 6A:
This category is to be called "plutonian objects."
) so today we were meant to wake up to 12 planets in our solor system. Are there? I haven't seen any news stories, so is it true? Is Charon the snowball classed as a planet, along with the rock of Ceres?
![[party]](/images/smilies/partytime.gif "Party [party]")
