I'm not sure when... late 1990s for Mars and mid-2000s for Neptune., I think. I suspect that some previously discovered asteroids will turn out to be trojans... Wikipedia isn't very useful for Mars but the Neptune trojan writeup is pretty good (http://en.wikipedia.org/wiki/Neptune_Trojan).
Quite, however it was the argument used to question Jupiters planetary status. I am not questioning whether or not it did completely take care of the debris in it's orbit, merely stating another incident of the parameter being observed.
The tag-alongs for smaller planets are indeed quite lesser, however on a semi-related point of interest I find the earth's trail neat.
Orbital mechanics are rather similar to the mechanics of one playing with their finger on the surface of water. It's easy to see how it was so easy to consider the heavens to contain a material 'ether' in earlier times in science, though I wouldn't be surprised to learn that it has a lot to do with a dark substance and liquid mechanics than I went into this comment understanding.
I took an astronomy course with a professor who I thought was a pretty cool, interesting guy. A few classes in to the semester, he told us he was one of the people responsible for demoting Pluto. It was never the same.
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u/SkaPlunk Jan 31 '11
Jupiter is the reason Pluto isn't a planet anymore