I've often wondered: is it possible for a grouping of asteroids to have a highly elliptical orbit and pass Earth's distance to the sun very infrequently, say every X million years?
Is it possible that there is some very regular chance that the Earth would get pummelled, but only on extremely long time spans? How would we know or not know?
The grouping is hard to figure out, as gravity would likely pull them together. But if a comet approached nearer the sun, or swung by some high gravity planet, it might break up into a few smaller comets along the way. An example of a recent famous comet that broke up is Shoemaker Levy 9.
I think many that we know about have orbits in the thousands of years or less, with some known in the millions. But would it be possible for a huge grouping or sequence of them to maintain such an orbit together?
