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Pluto is a Planet!

A while back at work one of our daily "Fact or Crap in Spaaaaaaaaace" questions, the question I believe was "How many planets are there?"  I viewed this as a trick question —not terribly uncommon in FoC.  I knew the answer was going to come back as "8", but I, as the curmudgeonly old man at work, answered "9" which is the correct answer…at least when I learned about the planets.  But for FoC I was incorrect because it's answer is based on the current —and incorrect in my mind, definition of what is a "planet".  So, who's right?

Well, it depends who you ask.  From February 18, 1930 until August 24, 2006 the answer was an equivocal "9".  But after that, the answer became "8".  What?  Well, you see, back in 2006 the International Astronomical Union (IAU) General Assembly voted on a number of resolutions including numbers 5A, 5B, 6A and 6B.  The passage of these resolutions changed everything by formally defining what is a "planet".  So resolution 5A became a deathblow to our dear friend Pluto.  To be a "planet" by this definition you now have to meet three criteria:

  1. It must orbit the sun.
  2. It must have significant enough mass to become a round(ish) object.
  3. It must have cleared the neighborhood of it's orbit.
So what's the problem for Pluto?  Well it's got #1 and #2 covered, but unfortunately it hasn't cleared its neighborhood of other objects.  So by the new IAU definition, Pluto was deemed to no longer be a planet.  Here's a short article on How Many Planets are in the Solar System? (Which is clearly incorrect!)

Anyhow, resolution 5B deemed the other 8 planets to now be "classical planets."  6A deemed Pluto a "dwarf planet" and then 6B seems to be Pluto's consolation prize (or should that be constellation? yuk, yuk) by deeming that dwarf planets shall be categorized as "plutonian objects."  Gee thanks.  76 years as a planet all gone, just like that.

So what brought this all up in my head again?  A couple of weeks ago there was an episode of Nova called The Pluto Files that discusses the whole thing.

And so, if for no other reason than "I learned it that way", Pluto should at the very least be grandfathered in as a planet.  It always hase been and always will be a planet in my mind.  Nine planets, just as I was always taught.  So I'm okay with the IAU's definition as long as my Pluto gets to still be a planet!