Re: Comet Tails
Every time a comet comes back close to the Sun, it replenishes its path with more ice particles and dust; so, it's obvious there is a torus of matter that corresponds to the entire path of the comet around the sun. If this were not so, there wouldn't be Perseids every year around august 13th, as the comet has long gone back into the far reaches of the solar system. The spreading of the matter is very difficult to predict if one wants to have a good sight of the shower of falling stars (Leonids on november 17th), but it can be predicted successfully, like in 2001.
Raoul