Universe 'too fascinating'
2006-08-23 06:55
Prague - In coming up with the definition
of a planet, astronomers hoped to bring order to the way we look
at solar systems. Instead, they created a big bang.
A committee formed by the International Astronomers Union
(IAU) has proposed that to be called a planet, a celestial body
must be in orbit around a star while not itself being a star.
It also must be large enough in mass for its own gravity to
pull it into a nearly spherical shape.
The new definition - the first time the IAU has tried to
define scientifically what a planet is - means three new
planets will be added to the current nine, and opens the door to
dozens more which are seen fitting the description.
Reaction to the proposal, which will be voted on this
Thursday by some 2 500 astronomers and scientists, has hit the IAU's annual conference in Prague like a meteor.
"The desire to put everything in neat little boxes is
admirable but can be overdone, particularly when the boxes
become contorted to include some objects and exclude others.
"The universe is too complex and too fascinating to fit everything into neatly described categories," said Paul Weissman, an IAU delegate from the Jet Propulsion Laboratory in the United States.
'Stamp collecting, not science'
"Often, the most interesting objects are the ones that
refuse to be categorised simply. Anally pursuing such a goal is
stamp collecting, not science."
The need to define what it takes to be a planet stems from
technological advances that enable astronomers to look further
into space and to measure more precisely the size of celestial
bodies in our solar system.
Under the new definition, schoolchildren will be relieved to
know that, just as they were taught, Pluto will remain a planet.
But it would also fall into a newly created category called
plutons, which are distinguished from classical planets in that
they take longer than 200 years to orbit the sun.
Pluto would be joined in this new category by Xena and Charon, while another, Ceres, would be known as a dwarf planet.
"The proposed change will lead to confusion and near constant
turmoil for no really good reason. The main beneficiaries of the
(definition) if approved, are likely to be publishing companies
and textbook authors," one IAU delegate said.
Not everyone agrees.
"The definition seems to be reasonable. It addresses whether
asteroids and Kuiper Belt objects (including Pluto) are planets
in a rational way," said Paul Withers, a research associate
professor in the Centre for Space Physics at Boston University.
"The debate is likely to continue after the IAU meeting,
even if the resolution is approved ... In the end, what we call
these objects in our solar system doesn't really matter. What
matters is what they tell us about the formation and history of
our little corner of the universe."
Geologists have also entered the fray, complaining at the
use of plutons as a new category - a term they already use to
describe a body of igneous rock that solidified below the
Earth's surface.
"Well, if we are changing the dictionary definition of a
planet, why stop there. I guess they could change other terms
such as plutons as well," quipped one delegate.