Why do some comets have two tails?
Comets produce gas and dust in large quantities as they approach the Sun and
the inner solar system. The gas can be come 'photoionized' by the harsh
ultraviolet light from the Sun, so that comet tails contain a complicated
mixture of dust, ionized gas and neutral gas. The reason you get two tails is
because the cometary ionized and neutral gases go one way in space because
they are effected by the magnetic fields and gases in the solar wind. The dust
however, is less sensitive to the solar wind and continues to go its own way.
generally, the dust tails follow along the orbit of the comet, and the gas
tail follows in the direction of the outgoing solar wind at that location.
Sometimes the ionized gas partakes of complex rapidly changing motions as it
interacts with kinks in the solar magnetic field to produce propagating cusps
and kinks in the tail which propagate from the head of the comet down the
gas tail in a matter of hours and days.
Copyright 1997 Dr. Sten Odenwald
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