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Encke's Comet

Faint comet having the shortest orbital period (about 3.3 years) of any known, first observed in 1786. It was the second comet (after Halley's Comet) to have its period determined (1819), by Johann Franz Encke (1791–1865). Encke also found that the comet's period decreases by about 2 hours in each revolution and showed that this effect could not be explained by the planets' gravitational influence. Its period continues to decrease, though more slowly, and appears to be related to the effects of outgassing.

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