Printer Friendly

Xena's warriors face a stellar task to win her recognition as a planet.

As every school pupil knows, there are nine planets circling the Sun - but that may no longer be the case in a few days time. Astronomers meeting in Prague are engaged in a hot debate about what constitutes a 'planet'.

After their decision, due to be announced next week, school science books may have to be rewritten.

The controversy has gone on since astronomers started discovering planet-like objects in a region on the fringe of the solar system known as the Kuiper Belt.

But the stakes were raised when US astronomer Professor Mike Brown and colleagues at the California Institute of Technology spotted a Kuiper Belt object bigger than Pluto, the 'ninth' planet and the most distant member of the Sun's family.

The object, 2003 UB313, nicknamed Xena, divided astronomers with sharply differing opinions.

Some insisted that despite its size it did not make the grade as a planet, and nor did the other Kuiper Belt objects.

Others claimed it was time to change the whole definition of what is meant by the word 'planet'. They argued that if Pluto was a planet, so was Xena, and possibly some of its Kuiper Belt cousins.

A third group maintained that Pluto should lose its planetary status and be demoted to the rank of Kuiper Belt object.

Pluto, discovered in 1930, is a ball of ice just 1,467 miles across and very different from more familiar planets such as the Earth, Mars, Jupiter or even its nearest neighbour Neptune.

After months of wrangling the International Astronomical Union (IAU) is now determined to end the argument.

About 3,000 scientists are attending the Prague meeting to thrash out the planet question and take a vote.

Director of Cardiff University's centre for astrobiology Professor Chandra Wickramasinghe, said that because Pluto has been known as a planet, studied as a planet and has all the classic characteristics of a planet, it should keep its classification.

But he added, 'I think the naming is unimportant. Whether it's called a planet, a planetoid, or a Kuiper-Belt object, is to my mind largely irrelevant. What's more interesting is that the object has enormous value for studying the beginnings of the solar system. Along with the comets it was one of the first solid objects to condense and so it might hold the secrets to the solar system.'

Dr Peter Bond, of the Royal Astronomical Society, said, 'The problem is Pluto is very small, much smaller than any of the other planets. We've now started finding objects nearly as big as Pluto, and one that is bigger. So the big question is, how do you define a planet? By its mass, size or shape, or some other way?

'People are now tending towards saying there are different classes of planets. You start from the old idea that a planet is a large spherical object that goes around the Sun.

'Then you say Pluto is a lot smaller than even Mercury, so let's divide it up not just according to size, but a variety of other qualities as well. You have the four rocky planets, including the Earth, the gas giants like Jupiter and Saturn, and then you've got ice dwarfs which would include Pluto and other large Kuiper Belt objects. These objects would still be planets, but a sub-category.

'At the moment if you took that view you'd increase the number of planets from nine to 10, but there might be more in the future if other objects like UB313 are discovered.

'The problem is there are a number of objects a little bit smaller than Pluto, so where do you draw the lower boundary for calling something a planet? Theoretically you could already go up to 12 or 13.'

Despite the difficulties, Dr Bond said he expected the IAU to come to a decision by about Wednesday next week.
COPYRIGHT 2006 MGN Ltd.
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 2006 Gale, Cengage Learning. All rights reserved.

 Reader Opinion

Title:

Comment:



 

Article Details
Printer friendly Cite/link Email Feedback
Publication:Western Mail (Cardiff, Wales)
Date:Aug 15, 2006
Words:642
Previous Article:'It was a hobby at first.
Next Article:United Counties set for rename and revamp.

Terms of use | Copyright © 2014 Farlex, Inc. | Feedback | For webmasters