Pluto no longer a planet

[arjan de lumens]

While the "cleared its orbit" criterion sounds really vague, it is fairly easy to extend it to a more elaborate and precise criterion. What is generally the case with the major planets is not that their orbits are totally free of other objects sharing the orbit, but rather that every object that shares an orbit with a major planet has a clear orbital relationship with the major planet, imposed on it by the major planet. Examples of such relationships would be:

• The other object orbits the planet (what we call a "moon")
• The other object is trapped within the planet's Lagrange points (e.g. the Trojan asteroids of Jupiter)
• The object has been forced into an orbital resonance with the planet (e.g. Neptune has forced Pluto and several other objects into a 3:2 orbital resonance)

The problem with a criterion like this is that even though it itsn't terribly complex, it does not easily fit into the 1-sentence soundbite format everyone wants these days.

Incidentally, the orbital resonance between Neptune and Pluto means that they never actually get closer to each other than ~19 AU, even though the points where their orbits are closest to each other are much closer; as such, one could argue that Pluto is effectively cleared from Neptune's orbit as it is.

 

[Bigus Dickus]

Yeah, that makes sense. I think you're right - the precise definition doesn't fit into the one sentence summary, which is of course what all the media will be using.

 

[Simon F]

Meet 134340

 

[nutball]

Meet Eris

 

[pascal]

I vote for Pluto back.

 

[London Geezer]

This proves that, after all is said and done, size does matter a lot.