hungrytiger: (Default)
1) The recent news about Pluto being demoted to the new "minor planet" category got me wondering more about the history of Ceres and the other large asteroids. In the first half of the 19th century, Ceres, Pallas, Juno, and Vesta were all considered planets and I was wondering what reaction, if any, there was to their demotion. I found an interesting article on how the asteroids began to be considered minor planets which includes an interesting note about how early text books like First Steps to Astronomy and Geography (1828) listed the planets as, "Eleven: Mercury, Venus, the Earth, Mars, Vesta, Juno, Ceres, Pallas, Jupiter, Saturn, and Herschel." [Herschel - was an early alternate name for Uranus, it comes from its discoverer.] The article has much discussion about how the astronomical community accepted the fact that Ceres & Co. weren't planets, but sadly mentions nothing reactions outside that community (I suspect that there probably wasn't much).

2) As expected, there's already a backlash about the newest IAU decision, which does appear to have been made by a tiny percentage of IAU members. A good write up on how other astronomers are reacting can be found in this article by a BBC science reporter. For a good overview on the details of this back and forth and what the points of the debate are, read the Wikipedia overview of the IAU drafts.

3) I have no particular problem with classifying Pluto, Ceres, & Charon as minor planets. Calling them planets did open the door for many, many other objects to be included in that category. The IAU president of planetary systems science said that if Pluto stayed a planet, "By the end of the decade, we would have had 100 planets." On the other hand though, I don't like the term "dwarf planet." If we're going to define certain objects as dwarf planets, how can we include Mercury, Venus, Earth, and Mars in the same category as Jupiter and Saturn. Should't Jupiter and Saturn be "Giant Planets?"

4) In the end though, this whole thing is silly [which, I think, is why it appeals to me so much]. It's like trying to define the difference between a large hill and a small mountain; it's a cultural thing and assigning a strict definition to it makes things worse unless the definition is so clear that it leaves not ambiguity. [And BTW, I thought that The Englishman Who Went Up a Hill But Came Down a Mountain, a 1995 romantic-comedy on that topic, was a pretty fun movie.]
hungrytiger: (Nemo - Balloon)
The number of planets changes yet again as the International Astronomical Union went back on it's earlier opinion and voted to strip Pluto of its planetary status after all.


hungrytiger: (Default)

April 2011

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