This Sky and Telescope article says that Marsden, director of the Minor Planet Center, has been trying to demote Pluto for over twenty years, without success. He justifies the reclassification because it "might eliminate its inadvertent rediscovery by observers who occasionally mistake it for a faint new object." Anybody who "forgets" about Pluto is a little careless, don't you think?

Accusing the other side of personal motives is unfair. That opens up a can of worms--both sides are susceptible, and it's unfair. For instance, is Brian Marsden trying to "take over" Pluto, as director of the Center? What was his response when it was suggested that Pluto be classified as trans-Newtonian object TN/1? He opposed the creation of a new classification system--which doesn't seem to fit with the explanation that we are trying to categorize these objects appropriately. TNOs are as like the objects of the asteroid belt as they are planets.

I suggested those criteria for planets for consideration because we don't have any. As the Sky and Telescope article mentions, Pluto satisfies almost any criteria for planethood. Is there anything wrong with the criteria I mentioned? Would Ceres really be considered a planet also?

There are a few asteroids that satisfy all criteria, except #3. 1 Ceres seems distinctly football shaped (though that Sky and Telescope article, in its last paragraph, seems to say otherwise), 4 Vesta has a noticeable non-sphericity, and although I didn't find a photo of 2 Pallas, its dimensions are listed as 570 x 525 x 482km. 10 Hygiea has a radius of 215, but I didn't find any axial information -- so it might be a planet under this definition, but I doubt it. Those are the only asteroids with a radius greater than 200km.

TNO Varuna may have a radius of about 450km, but other TNOs discovered appear to be around 200km or less. I only really added rule 5 to make sure very small objects weren't considered--otherwise, a baseball thrown out the window of a planetary probe would satisfy all the other criteria!
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rocks

<font size=-1>[Fixed format, added comment on rule 5]</font>

<font size=-1>[ This Message was edited by: GrapesOfWrath on 2001-12-31 09:37 ]</font>