Pluto: And then there were eight
Pluto has just been demoted. The celestial body, long known as one of the nine planets of the solar system, will now be considered a "dwarf planet," the General Assembly of the 2006 International Astronomical Union ruled in a vote Thursday in Prague, Czech Republic.
Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune will be defined as "classical planets."
The IAU said in a statement on Thursday that the definition for planet is now officially "a celestial body that (a) is in orbit around the Sun, ( 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."