08-16-2006, 12:25 PM
An influential group of Astronomers meeting in Prague are deciding whether our solar system has 12 planets, not nine.
They have agreed on a draft proposal for redefining what constitutes a planet.
A new kind of planet, the pluton, differs from classical planets in that they have orbits round the Sun that take longer than 200 years to complete, and their orbits are highly tilted and non-circular.
All these characteristics suggest that they have an origin different from that of classical planets.
If plutons are approved at the meeting in the Czech capital, it would mean there are 12, not nine planets, and more could be added to the list in the future.
They include eight "classic" planets - Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune - three "plutons," one of which is Pluto, and Ceres, the largest asteroid.
The other plutons besides Pluto are Charon and the newly discovered object 2003 UB313, which has not been named officially but is nicknamed Xena.
Charon is currently described as a moon of Pluto, but because of its size some experts consider it a twin planet.
Ceres is the largest object in the asteroid belt between Mars and Jupiter, and like a planet is spherical in shape.
A resolution to accept the new planet definition will be voted on by members of the International Astronomical Union (IAU) next Thursday, August 24.
If passed, the days of simply learning the names of the nine planets will be over for the world's schoolchildren.
In future, many more planets could join the Sun's family as other plutons are discovered.
A dozen "candidate planets" are already on the IAUs watchlist. They include Varuna, Quaor and Sedna, all Pluto-like objects residing within a region on the fringe of the Solar System known as the Kuiper Belt.
Jan 19: Nasa launches Pluto probe
http://www.itv.com/news/world_9721ad2a55...946f4.html
They have agreed on a draft proposal for redefining what constitutes a planet.
A new kind of planet, the pluton, differs from classical planets in that they have orbits round the Sun that take longer than 200 years to complete, and their orbits are highly tilted and non-circular.
All these characteristics suggest that they have an origin different from that of classical planets.
If plutons are approved at the meeting in the Czech capital, it would mean there are 12, not nine planets, and more could be added to the list in the future.
They include eight "classic" planets - Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune - three "plutons," one of which is Pluto, and Ceres, the largest asteroid.
The other plutons besides Pluto are Charon and the newly discovered object 2003 UB313, which has not been named officially but is nicknamed Xena.
Charon is currently described as a moon of Pluto, but because of its size some experts consider it a twin planet.
Ceres is the largest object in the asteroid belt between Mars and Jupiter, and like a planet is spherical in shape.
A resolution to accept the new planet definition will be voted on by members of the International Astronomical Union (IAU) next Thursday, August 24.
If passed, the days of simply learning the names of the nine planets will be over for the world's schoolchildren.
In future, many more planets could join the Sun's family as other plutons are discovered.
A dozen "candidate planets" are already on the IAUs watchlist. They include Varuna, Quaor and Sedna, all Pluto-like objects residing within a region on the fringe of the Solar System known as the Kuiper Belt.
Jan 19: Nasa launches Pluto probe
http://www.itv.com/news/world_9721ad2a55...946f4.html
