what a Comet?

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Comet is a cloud of frozen gas, ice, dust and rock and travels round the Solar System in paths or orbits. The brightest comets are only a few hundred kilometres in size, but their bright tails may be millions of kilometres long. A complete orbit by a comet is called its period.
As a comet travels towards the Sun, the Sun's rays knock particles out of the comet and push them away to make a long tail. The tail is made up of glowing gas and dust. 

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