Pluto demoted, no longer a planet

For decades, it?s been confused with a cartoon dog and ridiculed as a puny poser. Now Pluto, the solar system’s consummate cling-on, has suffered its worst humiliation: It?s not even a planet anymore.

After a tumultuous week of clashing over the essence of the cosmos, leading astronomers Thursday stripped Pluto of the planetary status it has held since its discovery in 1930. The new definition of what is ? and isn?t ? a planet fills a centuries-old black hole for scientists who have labored since Copernicus without one.

The historic vote by the International Astronomical Union officially shrinks Earth?s neighborhood from the traditional nine planets to eight.

But the scientists made clear they?re as sentimental as anyone else about the ninth rock from the sun.

Jocelyn Bell Burnell ? a specialist in neutron stars from Northern Ireland who oversaw the proceedings in Prague ? urged those who might be ?quite disappointed? to look on the bright side.

?It could be argued that we are creating an umbrella called ?planet? under which the dwarf planets exist,? she said, drawing laughter by waving a stuffed Pluto of Walt Disney fame beneath a real umbrella. Later, she hugged the doll as she stood at the dais.

?Many more Plutos wait to be discovered,? added Richard Binzel, a professor of planetary science at the Massachusetts Institute of Technology.

The decision by the prestigious international group spells out the basic tests that celestial objects will have to meet before they can be considered for admission to the elite cosmic club.

For now, membership will be restricted to the eight ?classical? planets in the solar system: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune.

Much-maligned Pluto ? named for the God of the underworld ? doesn?t make the grade under the new rules for a planet: ?a celestial body that is in orbit around the sun, has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a … nearly round shape, and has cleared the neighborhood around its orbit.?

Pluto is automatically disqualified because its oblong orbit overlaps with Neptune?s.

Instead, it will be reclassified in a new category of ?dwarf planets,? similar to what long have been termed ?minor planets.? The definition also lays out a third class of lesser objects that orbit the sun ? ?small solar system bodies,? a term that will apply to numerous asteroids, comets and other natural satellites.

Experts said there could be dozens of dwarf planets catalogued across the solar system in the next few years ? handing the world?s school teachers a challenge.