Space trash

While watching something called "Comets: Prophets of Doom" on the History channel, a few thoughts came to mind. One of the things talked about in this documentary was that they were not sent by God as omens but were subject to the forces of gravity. We know this to be true today, as opposed to our ancestors who thought they were mystical objects sent to forecast doom and gloom, thanks to the work of Isaac Newton and Edmund Halley and others.

It makes sense. Halley's comet returns at reasonably predictable periods of 75-76 years. It is a "short period" comet, many others take thousands of years to traverse their orbits. This fact bothers me a little. Probably because I am not a physicist. I do not understand the math and I can't quite grasp the concepts involved. I am sure it is my failing.

A comet is a small thing; tiny, having very little relative mass. Its orbit is an elliptical one which takes it out past Neptune before it returns. What brings it back is the gravitational pull of the sun. At some point in history, it was pulled from its original path by the gravitional pull of Neptune, it is theorized, and was slung toward the sun thereby "capturing" it and restricting it to an orbit within our solar system. All of this had to do with its original velocity, the relative mass of Neptune, and the relative mass of the sun. And math that is so far beyond my capabilities that it may as well be magic.

One thing that bothers me is that in all the millenia that Halley's Comet has been in its current orbit, nothing has altered that orbit significantly that we know about. It's possible that it has been altered many, many times. I just don't know that. The inference I made was that comets are already in orbits much greater than those that orbit within our own solar system and that these occasionally pass by our system close enough to be affected by Neptune because a number of factors happened to be "right" at the time. In simple terms, Neptune had to be at its apogee, the comet at a specific distance (not too close, not too far) that allowed it to be drawn toward Neptune, and the speed of the comet had to be sufficient to allow it to be drawn into a trajectory that will send it toward the sun but not into it. In summary, everything had to be just right.

What was the original orbit of, say, Halley's Comet? What are the orbits of other comets that have not yet been captured by our insignificant little solar system? What are they currently orbiting around, if anything? Doesn't that imply that there is some greater mass out there attracting these things? Are they orbiting around the galactic core, for instance? If the core is a black hole then that makes some sense.

As I said, I don't know enough to even ask intelligent questions or understand the answers if I did.

It still piques my curiosity, though.