or (And your little dog, Goofy, too!) It’s official, the International Astronomical Union (IAU), founded in 1919, has defined (I never had that much time in my life to define something -- most of my identify and define tests were given in the time frame of 40 minutes, slackers.) what a planet is: 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. According to this definition, Pluto has been demoted from a planet to a dwarf planet. A dwarf 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, (c) has not cleared the neighbourhood around its orbit, and (d) is not a satellite. Pluto is a dwarf planet by the above definition and is ...
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