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AHA! another comet question. Comets actually have two tails:
the dust tail and the gas or ion tail. The names should tell
you what's in them. Both tails always point *away* from the Sun,
independent of the comet's motion. The dust tail is formed of
solid particles escaping from the cometary nucleus into their own
solar orbits and may be slightly curved. It shines with reflected
sunlight. The ion tail is pushed straight back from the coma by
the solar wind and solar radiation pressure and glows from the
fluorescence of the ionized molecules CO+, N2+, OH+, CO2+, and CH+.
Some comets are also surrounded by huge (bigger than the Sun)
clouds of hydrogen gas.
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