Is there a comet belt

Answer 1

You might think of the proposed Oort Cloud as a sort of "comet belt". Jan Oort's theory is that all comets will exhaust their volatile mass and fall apart or collide with a planet. The solar system has been in existence for 4.5 billion years, and no comet could possibly survive so long. And yet we still see comets!

Oort proposed a "cloud" of cometary material in very distant orbits far beyond the orbits of Neptune. Occasional near collisions or interactions with other objects might disturb some objects by their mutual gravitational attraction, and periodically a object would fall into the inner solar system as a comet.

There was even a theory that there might be a large unknown planet out there somewhere, which would somehow fling large numbers of cometary bodies like birdshot into the inner solar system. The name of the proposed planet was to be "Nemesis".