Recently, I attended a lecture at my university entitled "The Life and Death of a Star-Grazing Comet" presented by John Raymond, an astrophysicist at Harvard Smithsonian. In this lecture, he talked about Comet Lovejoy and how it allowed us to help study the corona of the sun. As the comet was so big, it survived going through the corona of the sun and allowed us to understand it (since we saw it come out the other side before it vaporized about a day later). However, when he showed a picture of the orbit of the Kreutz family of comets (attached) depicting an extremely elongated orbit as it approaches our sun. From what I have always believed, the earth is gravitationally "locked" to the sun; that is it is orbiting the sun and the sun is the major body influencing the Earth's motion (keeping it going around the sun and not another body). I was wondering how a comet can get such an elongated orbit and still be gravitationally locked to the sun in the same way, that is we can predict when it will return because it has a very specific orbital period. If something is going so far out in the solar system, why does it not get "locked" to another body that it gets closer to on the way to and from the sun? If the orbit is so elongated, why doesn't it fall into orbit of another large body somewhere else in the solar system? Is it because of where they come from, as in nothing out where they come from is massive enough to hold a comet in their orbit? Edit: in the picture, as I'm sure you guessed, the thing, very elongated lines coming from the bottom of the page are the orbital paths of the Kreutz family of sun-grazing comets.