Pluto Could Lose Planet Status

June 21, 2006
Pluto Could Lose Planet Status
The artist's rendition shows "Sedna" in relation to other bodies in the solar system, including Earth and its Moon; Pluto; and Quaoar, a planetoid beyond Pluto that was the largest known object beyond Pluto. Image courtesy: NASA/JPL-Caltech

At its conference this August, the International Astronomical Union (IAU) will make a decision that could see Pluto lose its status as a planet.

For the first time, the organisation will be officially defining the word "planet", and it is causing much debate in the world of astronomy.

There is only one thing that everyone seems to agree on: there are no longer nine planets in the Solar System.

The debate has been brought to a head by the discovery of a potential 10th planet, temporarily named 2003 UB313 in January 2005. This new candidate planet is bigger than Pluto.

The question now facing the IAU is whether to make this new discovery a planet.

Pluto is an unusual planet as it is made predominantly of ice and is smaller even than the Earth's Moon.

There is a group of astronomers that are arguing for an eight-planet SolarSystem, with neither Pluto or 2003 UB313 making the grade as a planet; but a number of astronomers are arguing for a more specific definition of a planet.

One of these; Kuiper Belt researcher Dr Marc Buie, of the Lowell Observatory in Arizona, has come up with a clear planetary definition he would like to see the IAU adopt.

I believe the definition of planet should be as simple as possible, so I've come up with two criteria," he said.

"One is that it can't be big enough to burn its own matter - that's what a star does. On the small end, I think the boundary between a planet and not a planet should be, is the gravity of the object stronger than the strength of the material of the object? That's a fancy way of saying is it round?"

This definition could lead to our Solar System having as many as 20 planets, including Pluto, 2003 UB313, and many objects that were previously classified as moons or asteroids.

One possible resolution to the debate is for new categories of planet to be introduced. Mercury, Venus, the Earth and Mars would be "rocky planets". The gas-giants Jupiter, Saturn, Uranus and Neptune would be a second category.

Whatever the outcome of this debate there is only one thing that we can be certain of; by September 2006 there will no longer be just nine planets in our Solar System.

Source: BNSC

Explore further: A chance for the Pluto-huggers? Scientist leads effort to restore underdog's planetary stature

Related Stories

Experts and audience contest Pluto's 'dwarf planet' status

September 22, 2014

Could the stars be aligned for Pluto to reassume its place in the solar system? The International Astronomical Union (IAU) voted in 2006 to demote Pluto from planetary status. But after an hourlong debate Thursday night between ...

NASA Pluto probe launch postponed (Update 2)

January 17, 2006

NASA postponed Tuesday the launch of the world's first probe to the icy, never-explored planet of Pluto after excessively strong winds put the liftoff at risk.

A recipe for returning Pluto to full planethood

February 20, 2015

A storm is brewing, a battle of words and a war of the worlds. The Earth is not at risk. It is mostly a civil dispute, but it has the potential to influence the path of careers. In 2014, a Harvard led debate was undertaken ...

Recommended for you

Three 'super-Earths' orbiting a cool dwarf star discovered

January 23, 2018

Using NASA's prolonged Kepler mission, known as K2, astronomers have found three new "super-Earth" exoplanets. The newly detected alien worlds orbit the cool dwarf star designated LP415-17. The finding is reported January ...

Scientist proposes new definition of a planet

January 23, 2018

Pluto hogs the spotlight in the continuing scientific debate over what is and what is not a planet, but a less conspicuous argument rages on about the planetary status of massive objects outside our solar system. The dispute ...

Dust storms linked to gas escape from Martian atmosphere

January 23, 2018

Some Mars experts are eager and optimistic for a dust storm this year to grow so grand it darkens skies around the entire Red Planet. This type of phenomenon in the environment of modern Mars could be examined as never before ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.