IAU refuses god of the underworld from “classical” club, Pluto demoted to dwarf plane

The icy rock named after the Roman god of the underworld has lost favor with the International Astronomical Union's (IAU) and been demoted to dwarf planet status. In the end, 2,500 scientists voted to place Pluto in a category outside of the “classical” planets.

After much debate and petitioning the group of astronomers meeting in Prague defined what constitutes a planet:

A planet is a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and (c) has cleared the neighborhood around its orbit.

As a result of this accepted definition Pluto is automatically disqualified because its oblong orbit overlaps with Neptune’s.

Just a week ago Pluto, along with Ceres, Charon and Xena were flirting with planetary status. Had the scientists voted in favor of the proposal it could have led to an influx of new planets in the future. Rather than be faced with that scenario, scientists focused on what made Pluto different than the eight “ classical” planets and found enough evidence that supported their contention that it no longer belonged in the same category as Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune.

For Charon fans the new definition was a real blow, Pluto’s largest moon not only lost planet status but didn’t even fit the criteria for dwarf planet recognition.

Perhaps Ceres can console Pluto. When discovered in 1801 Ceres was declared a planet only to be stripped of that title later. Pluto had been considered a planet since 1930 so it had a 76 year run in the solar systems exclusive club. Those 76 earth years equate to about 109 earth days on Pluto.