[meteorite-list] Pluto May Get Demoted After All

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Fri Aug 18 12:55:58 2006
Message-ID: <200608181653.JAA27383_at_zagami.jpl.nasa.gov>

http://www.space.com/scienceastronomy/060818_planet_newprop.html

Pluto May Get Demoted After All
By Robert Roy Britt
space.com
18 August 2006

The effort to define the term "planet" took a fresh twist today as two
competing proposals were put forth at a meeting of astronomers in Prague.

In one case, Pluto would be demoted to "dwarf planet" status, which would
mean it would not be a real planet at all.

Astronomers are split down the middle on the issue.

Eight planets or hundreds

On Wednesday, officials with the International Astronomical Union (IAU)
proposed a planet definition that would make Pluto's moon Charon a
planet. Several astronomers criticized the overall proposal as being vague
and the Charon aspect specifically for going too far in essentially
recasting too many small round objects as full-fledged planets. Eventually,
with new discoveries, there would likely be hundreds.

They also were critical of the proposed term "pluton" to describe Pluto,
Charon and other small round objects in the outer solar system that would be
planets under the new definition.

Today, a subgroup of the IAU met to discuss the proposal. A straw vote
was held in which only about 18 astronomers favored the proposal,
according to Alan Boss, a planet-formation theorist at the Carnegie
Institution of Washington. Another 20 or so said it should be reworked.
And about 50 favored an alternate proposal.

"Most of the speakers during the discussion favored the competing
proposal, which inserts the criterion that a planet must be 'by far the
largest body in its population of bodies,'" Boss told SPACE.com.

That means Pluto and Charon, being no larger than other objects in the
sea of rocks beyond Neptune, would not be planets. Pluto would be called
a "dwarf planet" rather than a pluton. That would be in keeping with
terminology used to describe small stars.

For example, brown dwarfs are low-mass stars that fail to produce the
thermonuclear fusion that powers real stars.

"The group loudly applauded that description of Pluto," said Boss, who
has been critical of the original IAU proposal.

But some astronomers - perhaps about half of those at the meeting - are
still rallying for Pluto to remain a planet.

50-50 split

"There is a very large community out there defending keeping Pluto in
the list," said Owen Gingerich, an historian and astronomer emeritus at
Harvard who led the seven-member IAU committee that generated the
original definition. Gingerich said correspondence on the issue has been
half in favor of the original definition and half against.

In a telephone interview from Prague, Gingerich acknowledged that in
today's meeting astronomers "seemed to be overwhelmingly opposed" to the
term plutons, but said "it's not clear why."

Gingerich said calling Pluto a dwarf planet but having it not really be
a planet is "almost self-contradictory and linguistically objectionable."

Calling Pluto a dwarf would be a demotion that makes sense to many
astronomers who say it was a mistake in the first place to call Pluto a
planet when it was discovered in 1930. The dwarf category would
essentially give higher status to the eight other planets in our solar
system, and it would open up a new category to be populated by dozens of
round objects already discovered out beyond Neptune and hundreds more that
are expected to be found.

Public sentiment

People on the street were far less interested in the whole debate than are
the astronomers.

"I guess astronomers must be getting bored and running out of things to
do," said 22-year-old college student Mark Ramos.

But in general, people favor keeping Pluto as a planet. "It's my
favorite planet," said Emika Watanabe, a preschool teacher from Tokyo.

That is a sentiment that astronomers have been wrestling with for about
seven years now. Most astronomers agree it would be scientifically
convenient to demote Pluto, but they're well aware of the potential
outcry from school children. That "cultural clash," as Gingerich put it,
has been one of the biggest stumbling blocks in the ongoing debate
over a planet definition.

Boss said the IAU has the authority to handle the debate however it
wishes. It could either amend the existing proposal or adopt the
competing proposal. The ultimate plan is to put something before the IAU
membership for a vote on Thursday, Aug. 24.

Gingerich said he would be meeting today with the IAU Executive
Committee as that group ponders the next move. He said the Executive
Committee "will undoubtedly come before the membership with a single
resolution. They may make some adjustments."
Received on Fri 18 Aug 2006 12:53:11 PM PDT