The resolution describes a dwarf planet as an object that:
* 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,
* has not “cleared the neighborhood” around its orbit,
* is not a satellite of a planet, or other nonstellar body.
This definition demotes Pluto from a planet to a dwarf planet because it has not cleared the neighborhood of its orbit (the Kuiper Belt).
This decesion was reached by a vote taken by the International Astronomical Union who were meeting in Prague. As late as last week it thought 3 more bodies were going to be named to planet-status, but instead we lost a “planet”, taking the population of our solar system down to 8.
Science is an ever changing field of study, but it seems, I don’t know, sad, that we lost Pluto! It was a planet from it’s discovery in 1930 until now, and now it just seems weird now it’s just some hunk of rock out there.
See? Poor little guy! Oh well. Have fun replacing all those models, charts, and text books in schools now that teach the system has 9 planets!