[an error occurred while processing this directive]
BBC News
watch One-Minute World News
Pluto vote 'hijacked' in revolt
By Paul Rincon
Science reporter, BBC News

Pluto pictured by the HST (Nasa)
Pluto (L), pictured with its largest moon, Charon, is now a dwarf planet





I have nothing but ridicule for this decision
Alan Stern, Southwest Research Institute

The vote took place at the International Astronomical Union's (IAU) 10-day General Assembly in Prague. The IAU has been the official naming body for astronomy since 1919.

Only 424 astronomers who remained in Prague for the last day of the meeting took part.

An initial proposal by the IAU to add three new planets to the Solar System - the asteroid Ceres, Pluto's moon Charon and the distant world known as 2003 UB313 - met with considerable opposition at the meeting. Days of heated debate followed during which four separate proposals were tabled.

Eventually, the scientists adopted historic guidelines that see Pluto relegated to a secondary category of "dwarf planets".

Drawing the line

Dr Alan Stern, who leads the US space agency's New Horizons mission to Pluto and did not vote in Prague, told BBC News: "It's an awful definition; it's sloppy science and it would never pass peer review - for two reasons.

Pluto discoverer Clyde Tombaugh pictured in 1980 (AP)
Pluto was discovered in 1930 by the American Clyde Tombaugh
"Firstly, it is impossible and contrived to put a dividing line between dwarf planets and planets. It's as if we declared people not people for some arbitrary reason, like 'they tend to live in groups'.

"Secondly, the actual definition is even worse, because it's inconsistent."







'Inconvenient arrangements'

Owen Gingerich chaired the IAU's planet definition committee and helped draft an initial proposal raising the number of planets from nine to 12.

The Harvard professor emeritus blamed the outcome in large part on a "revolt" by dynamicists - astronomers who study the motion and gravitational effects of celestial objects.

Artist's impression of New Horizons probe, Nasa
Named after underworld god
Average of 5.9bn km to Sun
Orbits Sun every 248 years
Diameter of 2,360km
Has at least three moons
Rotates every 6.8 days
Gravity about 6% of Earth's
Surface temperature -233C
US probe (above) visits in 2015

"Their revolt raised enough of a fuss to destroy the scientific integrity and subtlety of the [earlier] resolution."





"If everyone had to travel to Washington DC every time we wanted to vote for President, we would have very different results because no one would vote. In today's world that is idiotic. I have nothing but ridicule for this decision."

He added that he could not see the resolution standing for very long and did not plan to change any of the astronomy textbook he was currently writing.

But other astronomers were happy to see Pluto cast from the official roster of planets. Professor Iwan Williams, the IAU's president of planetary systems science, commented: "Pluto has lots and lots of friends; we're not so keen to have Pluto and all his friends in the club because it gets crowded.

"By the end of the decade, we would have had 100 planets, and I think people would have said 'my goodness, what a mess they made back in 2006'."

Shaking hands

Robin Catchpole, of the Institute of Astronomy in Cambridge, UK, said: "My own personal opinion was to leave things as they were. I met Clyde Tombaugh, who discovered Pluto, and thought, it's nice to shake hands with someone who discovered a planet.

Mike Brown (AP)
Mike Brown's discovery precipitated the Pluto crisis
"But since the IAU brought out the first draft resolution, I was rather against that because I thought it was going to be very confusing. So the best of the alternatives was to keep the eight planets as they are, and then demote Pluto. I think this is a far superior solution."


The critical blow for Pluto came with the discovery three years ago of an object currently designated 2003 UB313. Discovered by Mike Brown and colleagues at the California Institute of Technology, 2003 UB313 has been lauded by some as the "10th Planet".

Measurements by the Hubble Space Telescope show it to have a diameter of 3,000km (1,864 miles), a few hundred km more than Pluto. 2003 UB313 will now join Pluto in the dwarf planet category.

Mike Brown seemed happy with Pluto's demotion. "Eight is enough," he told the Associated Press, jokingly adding: "I may go down in history as the guy who killed Pluto."

New Solar System - not to scale (BBC)

Why Pluto has been stripped of its status as a planet

Pluto loses status as a planet
24 Aug 06 |  Science/Nature
Q&A: Pluto's planetary demotion
24 Aug 06 |  Science/Nature
Crunch time for Planet Pluto
20 Jun 06 |  Science/Nature
Pluto probe launches from Florida
20 Jan 06 |  Science/Nature
Distant world tops Pluto for size
01 Feb 06 |  Science/Nature
Mission guide: New Horizons
19 Jan 06 |  Science/Nature
The girl who named a planet
13 Jan 06 |  Science/Nature
Astronomers detect '10th planet'
30 Jul 05 |  Science/Nature

The BBC is not responsible for the content of external internet sites

Has China's housing bubble burst?
How the world's oldest clove tree defied an empire
Why Royal Ballet principal Sergei Polunin quit


Americas Africa Europe Middle East South Asia Asia Pacific