[AZ-Observing] Planets
- From: "Thom/TFW" <mthomj@xxxxxxxxx>
- To: az-observing@xxxxxxxxxxxxx
- Date: Thu, 24 Aug 2006 09:23:34 -0700
http://www.iau2006.org/mirror/www.iau.org/iau0603/index.html
IAU 2006 General Assembly: Result of the IAU Resolution votes
24. August 2006, Prague
.....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"1 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) shape2 , (c) has not
cleared the neighbourhood around its orbit, and (d) is not a satellite.
(3) All other objects3 except satellites orbiting the Sun shall be referred to
collectively as "Small Solar-System Bodies".
--------------------------------------------------------------------------------
1The eight planets are: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus,
and Neptune.
2An IAU process will be established to assign borderline objects into either
dwarf planet and other categories.
3These currently include most of the Solar System asteroids, most
Trans-Neptunian Objects (TNOs), comets, and other small bodies.
--------------------------------------------------------------------------------
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.1
"Wisdom denotes the pursuing of the best ends by the best means" Francis
Hutchenson a Scot philosopher
Thom
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