Jim Gibson asked:
Can anyone explain why there appears to be 2 tails in the animation that Rich posted?
Jim Cobb's explanation is basically correct. The Ion tail, sometimes called the plasma tail, is composed of atomic particles and is driven by the solar wind; it always points away from the sun (more or less). The dust tail, composed of solid particles of dust and rubble, (and the source of earthly meteor showers when we intersect a comet's orbit) basically streams along behind the comet in it's orbital path. Imagining the geometry in your mind's eye, you can see that the two tails can thus diverge by gross angles as the comet travels in it's path. Add to that the changing position of our viewpoint on the moving earth, relative to the comet, and the relative positions of the two tails change even more. Ion tails are typically bluish because they are generating their own photons at a specific wavelength, dust tails whitish to yellowish because they are just reflecting the broad-spectrum sunlight. __________________________________ Do you Yahoo!? Yahoo! Mail - now with 250MB free storage. Learn more. http://info.mail.yahoo.com/mail_250