Help me better understand how the laws of the solar system govern its structure. Given our solar system, could a (new) planet exist between two others? Supposedly, any body should gravitate towards one the other, true? So, if a planet were to exist between two others, it would have to exist along an orbit that coincides perfectly with the LaGrange point (should these two planets pass nearest each other) such that the (new) planet would remain unaffected by its neighbor on either side?
Along these lines, some SDopers may recall c.1978 there was a planetoid found just beyond Saturn’s orbit. Could this be why it was not pulled one way or the other to its doom?
Last, why aren’t comets pulled to their deaths? Especially the supposed short-period comet(s) trapped in an orbit between the Sun and Jupiter [although you’d think such a comet would be quite a familiar sight in the night sky]. Is it merely their velocity that keeps them successful in this precarious balancing act?
[While one can Google on these topics indivudally, I could not find one source that puts it all together.]
You might take a look at the Wikipedia article and the ScholarPedia article on the stability of the Solar System; they cover a lot of the ground you’re interested in.
It has nothing to do with Lagrange points really. In fact, if the new body you’re introducing is a planet, comparable in mass to the “old” planet, then the Lagrange points don’t exist for that body.
It’s true that all objects with mass pull on all other objects with mass, but it’s not inevitable that they’re going to get closer to each other as a result. If a body is orbiting the Sun, and the gravitational forces from everything else are small in comparison to the Sun’s force, then the body’s orbit around the Sun will remain fixed indefinitely.
Same basic reason. Their orbits are stable, or at least quasi-stable for long periods, because they never approach a planet too closely.
Their velocity is what gives them their orbit in the first place, so I guess you can think of that as part of the reason. But they’re not necessarily doing a “precarious” balancing act, as nearly all the comets in our solar system are the same age as the solar system.
To look at it another way, nearly everything in the solar system that had a “doomed” orbit was ejected or absorbed long, long ago. What remains therefore are the bodies that have well-behaved orbits.