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 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 neighborhood 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,
and (c) has not cleared the
neighborhood around its orbit and (d) is
not a
satellite.
(3) All other objects orbiting the
Sun, excluded satellites, shall be referred to
collectively as “Small Solar System Bodies”.
Notes:
1. The eight planets are: Mercury,
Venus, Earth, Mass,
Jupiter, Saturn, Uranus and Neptune.
2. An IAU process will be
established to assign borderline
objects into either dwarf planet and other categories.
3. The other objects include most
of the Solar System
asteroids, most Trans-Neptunian objects (TNOs), comets and other small
bodies.
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.