Translating the article for readers here:
MADRID: Pluto has ceased to be known as a planet; thus, the number of planets in the solar system has fallen from nine to eight. This was the conclusion reached at the end of the International Astronomical Union summit in Prague, which aimed to set a definition of 'planet'.
Astronomers around the world have spent two years debating the status of Pluto. This resulted from when Brown discovered a body, 2003-UB313, located 14.5 billion miles from Earth. The problem arose because this body proved to be larger than Pluto.
Pluto, discovered 76 years ago by American scientist Clyde Tombaugh (1906-1997), has been the subject of debate for decades owing to its size, which has officially been reduced year after year and currently is established at 2,300 kilometres in diameter.
This makes Pluto considerably smaller than Earth, which has a diameter of 12,750 kilometres — and also Earth's moon, which is 3,480 kilometres in diameter. It is also smaller than 2003-UB313, despite the latter's considerable distance from the sun.
Another argument is that Pluto does not have a normal orbit, which fails to run parallel to that of Earth and the other seven planets that do.
DEFINITION OF 'PLANET'
The definition of planet agreed upon in Prague has been awaited for years, including ten days of deliberation in the Czech capital. Finally, experts have concorded that planets and other bodies in the Solar System each fall into one of three categories:
- First category: 'A "planet" is a body in the Solar System that orbits the Sun in alignment and has enough mass to generate gravity by spinning, has forced itself into spherical form, and is able to clear any obstruction in its orbit.
- Second category: 'A "dwarf planet" is a body that orbits the Sun and generates enough force by spinning to render itself a sphere but is not a satellite and cannot clear all obstacles to its orbit.
- All other bodies are relegated to a category known as the "small bodies of the Solar System".
As a result, the number of planets is reduced to only the eight discovered before Pluto: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune (ordered by distance from the sun, nearest to farthest).
Pluto, discovered in 1930, has lost status as planet and is now officially a 'dwarf planet'.
TWO OPTIONS
Experts were faced with only two options for a common position. One was to demote Pluto to 'dwarf planet'; the other was to instate 2003-UB313, Ceres, Caponte, and 12 other bodies as planets.
As sessions wore on the position came closer and closer to being in favour of demoting Pluto, the fartest and coldest from the Sun, to dwarf planet.
On the other hand, the subject may be brought up again when the IAU convenes again in 2009 in Rio de Janeiro to come up with a name for 2003-UB313.
