The Constant of Constant Change...

I am a avid reader of blogs (makes sense, since I have one of my own and you, my two readers, are reading it). One of my favorites is the Bad Astronomy website by Phil Phlatt. On his blog, he talks about the changes in astronomy especially planetary astronomy and most especially since the meeting of the International Astronomical Union which is the governing body that decides on planetary names and such. The big discussion has been on how the answer the question "What constitutes a planet?" Many astronomers argue vehimently about this subject but the discovery of many smaller objects has brought the question to a head. The answer so far; a planet has to be round, move arond the sun, and be at least 500 miles in diameter. As a result, some astronomers that wanted Pluto to be demoted lost badly at the conference and now we have 12 planets not just nine ( we add Charon, formerly a moon of Pluto now the two tegether are a 'double planet' system; Ceres, which is just big enough to be a planet but resides in the asteoid belt and was discovered in the early 1800's; and 2003 UB 313 which is about twice the size of Pluto and has been nicknamed Xena by its discoverer). The planets are now divided into two groups: Classic large planets (all the regular planets but Pluto), and Plutons (Pluto, Charon, Xena, and Ceres). As a result of this change, certain astronomers have had to "eat crow" and the best is Alex DeGrasse Tyson, the director of the Hansen Planetarium in New York. Here's a clip of Steven Colbert giving him a bad time (courtesy of You Tube):