Tails of a Comet
The most visible and perhaps
beautiful parts of a comet are its two tails: the gas tail and the
dust tail. In fact, the tails gave comets their name. The word
"comet" comes from the Latin words aster kometes,
which means "long-haired star".
The gas tail of a comet is very
straight and narrow. It is composed of ionized gas molecules.
This tail is visible because the ionized gas molecules glow. The gas
tail forms because gas molecules in the cometís head are blown
outward by the solar wind. The solar wind is the fast moving cloud of
plasma which constantly shoots out of the Sun in all directions. The gas
tail thus always points away from the sun.
The dust tail consists of
dust particles, which are also blown outward from the cometís head.
This tail has a broader, more curved shape than the gas tail. The dust
tail is visible because the dust particles shine in sunlight. Sunlight
also forms the dust tail. The pressure of sunlight striking the dust
particles literally blows them away from the head of the comet.