How many years does it take for Halley's Comet to reappear?
International Halley Watch International Halley Watch Halley's Comet, named after English astronomer Edmund Halley who first demonstrated its periodicity, returns to the vicinity of the Sun and Earth approximately every 76 years. Since comets are believed to be the most primordial objects in the solar system, their study is of great importance to planetary science. At the time of the 1986 return (technically, "apparition") of the comet, astronomical telescopes and related instrumentation were vastly more sensitive than for any previous apparition. Consequently, the International Halley Watch (IHW) was organized to stimulate, standardize, collect, and archive observations of the comet. The initial plans were
Halley's Comet third comet past perihelion in 1986 (1986 III); and it was the ninth comet spotted in 1982 (provisional designation 1982i). The perihelion dates of each apparition are shown. The perihelion dates farther from the present are approximate, mainly because of uncertainties in the modelling of non-gravitational effects. Perihelion dates of 1531 and earlier are in the Julian calendar, while perihelion dates 1607 and after are in the Gregorian calendar. Halley's Comet is visible from Earth every 74–79 years. Halley's Comet Halley's Comet or Comet Halley, officially designated 1P/Halley, is a short-period comet visible from Earth every 75–76 years. Halley is