Halley's Comet or Comet Halley, officially designated 1P/Halley, is the best-known of the short-period comets and is visible from Earth every 7576 years. Halley is the only short-period comet that is clearly visible to the naked eye from Earth, and thus the only naked-eye comet that might appear twice in a human lifetime. Other naked-eye comets may be brighter and more spectacular, but will appear only once in thousands of years. Halley's returns to the inner Solar System have been observed and recorded by astronomers since at least 240 BCE. Clear records of the comet's appearances were made by Chinese, Babylonian, and medieval European chroniclers, but were not recognized as reappearances of the same object at the time. The comet's periodicity was first determined in 1705 by English astronomer Edmond Halley, after whom it is now named. Halley's comet last appeared in the inner Solar System in 1986 and will next appear in mid-2061.
Contributions by Serendipodous, The Singing Badger, and Wknight94.