Which comet is the only known short-period comet that is regularly visible to the naked eye from Earth?
Halley's Comet or Comet Halley, officially designated 1P/Halley, is a short-period comet visible from Earth every 75–76 years. Halley last appeared in the inner parts of the Solar System in 1986 and will next appear in mid-2061.
Halley's Comet is a great comet which is bright enough to be noticed by casual observers who are not looking for it, and become well known outside the astronomical community. Great comets are rare - on average, only one will appear in a decade.
Halley's returns to the inner Solar System have been observed and recorded by astronomers since at least 240 BC. Clear records of the comet's appearances were made by Chinese, Babylonian, and medieval European chroniclers, but, at those times, were not recognized as reappearances of the same object. The comet's periodicity was first determined in 1705 by English astronomer Edmond Halley, after whom it is now named.