Post by Salem6 on Aug 24, 2006 14:42:16 GMT
Astronomers meeting in the Czech capital have voted to strip Pluto of its status as a planet.
Pluto's status has been contested for many years
About 2,500 experts were in Prague for the International Astronomical Union's (IAU) general assembly.
Astronomers rejected a proposal that would have retained Pluto as a planet and brought three other objects into the cosmic club.
Pluto has been considered a planet since its discovery in 1930 by the American Clyde Tombaugh.
The ninth planet will now effectively be airbrushed out of school and university textbooks.
The decision was made at a meeting of the International Astronomical Union (IAU) in the Czech capital Prague. Over 2,500 astronomers had been voting on a formal definition of a planet.
"The eight planets are Mercury, Earth, Venus, Mars, Jupiter, Saturn, Uranus and Neptune," said the IAU resolution, which was passed following a week of stormy debate.
PLUTO - A 'DEMOTED PLANET'
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
Nasa probe visits in 2015
The IAU's proposal to raise the number of planets in the Solar System to 12, adding the asteroid Ceres, Pluto's "moon" Charon and the distant object known as 2003 UB313, met with opposition.
Robin Catchpole, of the Institute of Astronomy in Cambridge, told the BBC News website: "My own personal opinion was to leave things as they were; I met Clyde Tombaugh and thought how nice it was to shake hands with someone who had discovered a planet."
"But since the IAU brought out the proposal for new planets I had been against it - it was going to be very confusing. The best of the alternatives was to leave the major planets as they are and then demote Pluto. So I think this is a far superior situation."
Louis Friedman, executive director of the Planetary Society in California commented: "The classification doesn't matter. Pluto - and all Solar System objects - are mysterious and exciting new worlds that need to be explored and better understood."
Dwarf planet
Pluto's status has been contested for many years as it is further away and considerably smaller than the eight other planets in our Solar System.
Since the early 1990s, astronomers have found several other objects of comparable size to Pluto in an outer region of the Solar System called the Kuiper Belt.
Some astronomers have long argued that Pluto belongs with this population of small, icy "dwarf planets", not with the objects we call planets.
Allowances were once made for Pluto on account of its size. At just 2,360km (1,467 miles) across, Pluto is significantly smaller than the other planets. But until recently, it was still the biggest known object in the Kuiper Belt.
That changed with the discovery of 2003 UB313 by Professor Mike Brown and colleagues at the California Institute of Technology (Caltech). After being measured with the Hubble Space Telescope, it was shown to be some 3,000km (1,864 miles) in diameter, making it larger than the ninth planet.
Named after the god of the underworld in Roman mythology, it orbits the Sun at an average distance of 5.9 billion kilometres (3.7 billion miles) taking 247.9 Earth years to complete a single circuit of the Sun.
An unmanned US spacecraft, New Horizons, is due to fly by Pluto and the Kuiper Belt in 2015.
news.bbc.co.uk/1/hi/sci/tech/5282440.stm