The final resolution about pluto

The IAU... resolves that planets and other bodies, except satellites, in our Solar System be defined

into three distinct categories in the following way:

1. A ‘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, 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 fo its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly

round) shape , (c) has not cleared the neighbourhood around its orbit, and (d) is not a satellite.

3. All other objectsexcept satellites orbiting the Sun shall be referred to collectively as ‘Small Solar

System Bodies’.

The eight planets are: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune. An IAU process will be established to assign borderline objects into either dwarf planet and other categories.

These currently include most of the Solar System asteroids, most Trans-Neptunian Objects (TNOs), comets, and other small bodies.

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.