IAU updates scientific definition of planet to match current knowledge

I posted this because I had to see at least one thread header in this
newsgroup that states what the IAU did in the positive light that it
intended, instead of the negative media spin of the "IAU dumped Pluto."
That postive light was, to quote the preamble of the resolution
(appended): "Contemporary observations are changing our understanding
of planetary systems, and it is important that our nomenclature for
objects reflect our current understanding."

Among the things that science should do is (1) accrue new knowledge and
advance our understanding of the natural world, and (2) husband the
general public's conventional wisdom about the natural world.

The story is not the "IAU made the general public and school children
feel uncomfortable by changing the definition of planet and demoting
Pluto as a planet." The story is: "members of the IAU advanced our
knowledge and understanding of the structure of the solar system. Based
on more observations with new satellites and better telescopes over the
last 70 years, scientific terminology to describe our better
understanding of solar system structure is being improved to match this
improved understanding."

Science should not bow to popular linguistic whims of the general
public. What will be next? Something like: "We need to keep the
definition of 'evolution' within 'safe' boundaries, so we don't upset
the children and inconvenience textbook manufacturers."

The best gift that we can give to subsequent generations is an expanded
view of the natural world with an improved depth of understanding of
how the natural world works. To do otherwise is a disservice to the
next generation, regardless of whatever transient inconvenience it may
cause to them, to textbook manufacturers, to the builders of
planetarium displays, or to our own natural human desire to feel secure
in an familiar and stable view of the world around us.

Clyde Tombaugh is probably spinning in his grave on this, but not
because Pluto was demoted. He would be spinning in his grave because
retaining Pluto as a planet is - based on our improvements in our
understanding the solar system's structure over the last 70 years - bad
science. Tombaugh spent all those hours at the blink comparator in
order to advance our knowledge of the solar system. 70 years later his
efforts bore significant fruit, no doubt in part through the many
future astronomers that he inspired while teaching at New Mexico State
University from the 1950s to the 1970s.

I never met him or heard him lecture, but if alive today, he would
probably be dismayed at an attempt to cling to an outdated model of our
solar system. If alive today, rather than hand-wringing over the loss
of "his planet," Tombaugh would probably be expending his engergies to
get a peak into the eyepiece that Mike Brown (co-discover of 2003UB313)
is looking through.

Science marches on and I, for one, gladly will march with it.

- Canopus56

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http://www.iau2006.org/mirror/www.iau.org/iau0603/index.html

RESOLUTIONS

Resolution 5A is the principal definition for the IAU usage of "planet"
and related terms.

Resolution 6A creates for IAU usage a new class of objects, for which
Pluto is the prototype. The IAU will set up a process to name these
objects.

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".

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1 The eight planets are: Mercury, Venus, Earth, Mars, Jupiter, Saturn,
Uranus, and Neptune.

2 An IAU process will be established to assign borderline objects into
either dwarf planet and other categories.

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

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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

.

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