August 13, 2006

Pluto’s status attacked

By Alan Crosby

PRAGUE (Reuters) - Despite being the farthest planet from
Earth in our solar system, Pluto has come under attack from
astronomers and may be about to lose its status in the battle.

Some 3,000 astronomers and scientists from around the world
will meet in Prague this week to decide whether Pluto,
discovered in 1930, measures up to the definition of a planet.

In defining for the first time what exactly a planet is,
the International Astronomers Union (IAU) may be forced to
downgrade Pluto's status, or add as many as 14 others.

Such a decision would send shockwaves through the
scientific community, instantly outdate textbooks, and cause
educators to re-teach the basics of our solar system.

"The pivotal question is the status of Pluto, which is
clearly very different from Jupiter, Saturn, Uranus, and
Neptune," Owen Gingerich, professor of Astronomy and History of
Science emeritus a the Harvard-Smithsonian Center for
Astrophysics told Reuters.

Debate has raged within the scientific community over the
status of Pluto for decades after the planet was found to be
only one four-hundredths of the mass of the earth.

That discussion intensified in 2003 when astronomers at the
California Institute of Technology discovered UB 313. Nicknamed
Xena after the character in the television show, UB 313 is one
of more than a dozen celestial bodies in our solar system found
to be larger than Pluto.

Xena and Pluto are large icy bodies that reside in the
Kuiper Belt -- where thousands of floating bodies travel --
beyond Neptune. Images from the Hubble Space Telescope put
Xena's diameter at 1,490 miles or so. That is slightly bigger
than Pluto, which measures 1,422 miles across.

Gingerich is the chair of a committee that was asked to
come up with a definition of a planet and hand it to the IAU
general assembly, which runs August 14-25.

In the run-up to the assembly, emotions have been running
high in both directions.

Some have appealed to Gingerich's group not to downgrade
Pluto, saying it would disappoint children and throw our
understanding of the universe into chaos.

Others say let the chips fall where they may and seem to
relish the idea of overturning our current view of the

Gingerich said that modern technologies have allowed
scientists to delve into the solar system further, and in more
detail, than ever before. Therefore, it is no surprise that
questions on the fundamental assumptions of it are arising.

"Should it (Pluto), for historical reasons, be considered a
planet like the rest?" Gingerich asks, refusing to tip his hand
on how the seven-member group has agreed after deciding on the
wording in June.

Scientists say the group may make a new class of planets
that accepts large bodies such as Xena and Pluto that do not
measure up to the eight larger planets. They could also drop
Pluto's status as a planet or expand the list of planets to
include many similarly-sized bodies found in the solar system.