How can we distinguish a dust tail from a gas tail?
We can distinguish a dust tail from a gas tail by examining their spectrum. The dust tail has the same spectrum as the sun, dominated by absorption lines, showing that this tail is merely glowing by reflecting sun light. The gas tail on the other hand displays the spectrum containing emission lines due to the molecules of carbon, cyonogen carbon monoxide etc. Thus a dust tail is usually yellow while a gas tail may be blue or blue green. Also the dust tail consists of dust grains falling freely in the gravitational field of the sun. It therefore, forms a graceful curve while a gas tail is straight, showing kinks as it stays confined to the magnetic field lines.
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