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Path of the comet of 1661. Illustration from Cometographia (1668), by the Polish astronomer Johannes Hevelius, showing the path of the comet of 1661 through the constellations. Comets are bodies of rock and ice that orbit the Sun on elongated orbits lasting hundreds or thousands of years. When they pass into the inner solar system, the Sun heats them up and the ice melts, creating long tails of ice and dust that glow in the light from the Sun.
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