When is a planet not a planet? When your name is Pluto, of course.
Posted by: Marc Boucher in Space Exploration
So the wonderful people at the International Astronomical Union today voted in favour of a resolution which changes the definition of a planet. A planet is now defined as:
“RESOLUTION 5A … (1) 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 neighbourhood around its orbit.”
So based on this definition Pluto is not a planet as it has not “cleared the neighbourhood around its orbit”. What a crock of …
Pluto is now a Dwarf Planet which is defined as;
“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) shape2 , (c) has not cleared the neighbourhood around its orbit, and (d) is not a satellite.”
So with this decision we now have to teach the world what is and is not a planet and explain to them that there are only eight planets in the solar system. Regardless of whether Pluto is officially a planet or not, my company, SpaceRef, has a great site for Pluto and Kuiper Belt Objects called Pluto Today. It’s worth a visit.
And some last thoughts, think of the economic impact this decision will have. What economic impact you ask? Well all those school books around the world have to be changed and every solar system product will need to be changed. I think the DOW went down a point or two on this news. 
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