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Optical photograph of comet Giacobini-Zimmer taken on October 26, 1959. The comet was discovered in 1900 by M. Giacobini in France and independently rediscovered by E. Zinner in Germany in 1913. It has an orbital period of 6.5 years. A comet's nucleus is composed of ice and dust. As it nears the Sun some of the ice evaporates as its surface is heated. This gas becomes ionized and is drawn outwards by the solar wind to form a tail which points away from the Sun. The released dust may also form a second tail as it is pushed by radiation pressure.
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