on 7 May 2134, Halley will pass within of Earth. Its apparent magnitude is expected to be −2.0. Apparitions Halley's calculations enabled the comet's earlier appearances to be found in the historical record. The following table sets out the astronomical designations for every apparition of Halley's Comet from 240 BC, the earliest documented widespread sighting. For example, "1P/1982 U1, 1986 III, 1982i" indicates that for the perihelion in 1986, Halley was the first period comet known (designated 1P) and this apparition was the first seen in half-month U (the second half of October) in 1982 (giving 1P/1982 U1); it was the 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. See also List of Halley-type comets Halley's Comet in fiction Kepler orbit References Bibliography External links Synopsis of the Astronomy of Comets (1706 reprint of Halley's 1705 paper) Halley's nucleus by Giotto spacecraft (ESA link) Image of Halley in 1986 by Giotto spacecraft (NASA link) cometography.com 1P/Halley at CometBase database seds.org Orbital simulation from JPL (Java) / Ephemeris Donald Keith Yeomans, "Great Comets in History" A brief history of Halley's Comet (Ian Ridpath) Photographs of 1910 approach taken from the Lick Observatory from the Lick Observatory Records Digital Archive, UC Santa Cruz Library's Digital Collections Astronomical objects known since antiquity Comets visited by spacecraft Halley-type comets Meteor shower progenitors 001P 0001 Periodic comets Star of Bethlehem