[meteorite-list] Pluto still has hope as a planet??? "Pluto: Down But Not Out by R Britt

From: drtanuki <drtanuki_at_meteoritecentral.com>
Date: Thu Aug 31 18:46:10 2006
Message-ID: <20060831224603.33974.qmail_at_web53213.mail.yahoo.com>

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http://www.space.com/scienceastronomy/060831_planet_definition.html

Pluto: Down But Maybe Not Out
By Robert Roy Britt
LiveScience Managing Editor
posted: 31 August 2006
02:38 pm ET
 

If you did not like Pluto's demotion, don't give up
hope.

Arguments over the newly approved definition for
"planet" are likely to continue at least until 2009,
and astronomers say there is much that remains to be
clarified and refined.

While it is entirely unclear if the definition could
ever be altered enough to reinstate Pluto as a planet,
astronomers clearly expect some changes.

In a statement today, the largest group of planetary
scientists in the world offered lukewarm support for
the definition, which was adopted last week by a vote
of just a few hundred astronomers at the International
Astronomical Union (IAU) General Assembly meeting in
Prague.

Lukewarm support

The definition basically states that the eight worlds
from Mercury to Neptune are planets, and that Pluto
and other small round objects in the outer solar
system are not planets but will be referred to as
dwarf planets.

The wording has been heavily criticized as being vague
and arbitrary and failing to include planets around
other stars. One highly controversial aspect is the
idea that a planet must control a zone of space by
clearing it of other objects. In fact, Earth and some
of the giant planets have not cleared their
paths?asteroids cross the planetary orbits frequently
and in some cases orbit in lockstep with the planets.

Nonetheless, the Division for Planetary Sciences (DPS)
of the American Astronomical Society (AAS) "recognizes
the authority of the IAU to render a decision,"
today's statement reads. "All definitions have a
degree of fuzziness that requires intelligent
application: what does 'round' really mean? What does
it mean to 'control a zone'?"

The statement suggests there are at least three years
of wrangling ahead:

"These are technical issues to be addressed by
Division III of the IAU, currently chaired by Ted
Bowell, a fellow DPS member. There is still work to be
done, too, in constructing a definition that is
generally applicable to extra-solar planetary systems.
These and other changes, radical or moderate,
presumably will be addressed at the next IAU General
Assembly in Rio de Janeiro in 2009, and the DPS
community will continue to be involved in all stages
of this process.

Lack of authority?

Other astronomers have said or indicated that the IAU
decision might not carry much weight.

David Morrison, an astronomer at NASA's Ames Research
Center, was in Prague for the debates and the vote. He
called the resulting definition "reasonable" but
termed the IAU process "highly convoluted."

"The definition of a planet is not primarily a science
issue. Scientists can (and often do) use all sorts of
jargon," Morrison told SPACE.com. "This issue is of
interest because non-scientists, including writers of
science textbooks, want a definition. Now they have
one. But it is not obvious to me that planetary
scientists will adjust their terminology because of
the IAU votes."

The IAU's final proposal was lambasted by many
astronomers for having been slapped together at the
last minute and for not adhering to recommendations
from two separate committees. Morrison was on an IAU
committee of astronomers that debated for months on a
definition proposal. The one they adopted, Morrison
said, was approved by the committee in a vote of 11-8.
But it never saw the light of day. Ultimately, another
committee of seven, including historians, was formed
by the IAU, and the second committee's proposed
definition was scrapped too, in the last moments in
Prague.

"Is Pluto, then, still a planet? Yes and no," Morrison
said. "The answer is semantic, based on whether dwarf
planets are planets, just as dwarf pines are pines. I
would say that Pluto is a planet, but it is a dwarf
planet, and the first example of the class of
trans-Neptunian dwarf planets."

Lack of science

The whole debate, many astronomers say, has little if
anything to do with science.

Geoff Marcy, a researcher at the University of
California, Berkeley, has led the discovery of dozens
of planets outside our solar system. "The astrophysics
of planetary bodies is so rich and complex that
defining 'planet' has never been an issue under
discussion among professionals," Marcy said in an
email interview earlier this week.

Pressed on whether the definition made any sense,
Marcy said: "It makes no scientific sense to have a
definition that pertains only to our solar system and
not to other planetary systems."

The DPS represents 1,300 astronomers, about a third of
them from outside the United States. Today's statement
included a phrase that hints at the discontent felt
among many members and the likelihood that all is not
said and done:

"Ultimately, the definition of a planet will come
through common usage and scientific utility. There is
no need to throw away current school texts; Pluto has
not gone away."
Received on Thu 31 Aug 2006 06:46:03 PM PDT