1P/HalleyImage of Comet HalleyIn 1986, the European spacecraft Giotto became one of the first spacecraft ever to encounter and photograph the nucleus of a comet, passing and imaging Halley's nucleus as it receded from the sun. Image Credit: Halley Multicolor Camera Team, Giotto Project, ESA1P/Halley is often called the most famous comet because it marked the first time astronomers understood comets could be repeat visitors to our night skies. Astronomers have now linked the comet's appearances to observations dating back more than 2,000 years.Halley was last seen in Earth's skies in 1986 and met was met in space by an international fleet of spacecraft. It will return in 2061 on its regular 76-year journey around the Sun.NEXT CLOSE APPROACH TO THE SUNComet HalleyPerihelion:July 27, 206141YRS07MOS16DAYS14HRS44MINS12SECSThe History of Halley's CometUntil the time of English astronomer Edmond Halley (1656-1742), comets were believed to make only one pass through the solar system.But in 1705, Halley used Isaac Newton's theories of gravitation and planetary motions to compute the orbits of several comets. Halley found the similarities in the orbits of bright comets reported in 1531, 1607 and 1682 and he suggested that the trio were actually a single comet making return trips. Halley correctly predicted the comet's return in 1758-1759 — 16 years after his death — and history's first known "periodic" comet was later named in his honor.The comet has since been connected to ancient observations going back more than 2,000 years. It is featured in the famous Bayeux tapestry, which chronicles the Battle of Hastings in 1066.In 1986, an international fleet spacecraft met the comet for an unprecedented study from a variety of vantage points. The science fleet included Japan's Suisei and Sakigake spacecraft, the Soviet Union's Vega 1 and Vega 2 (repurposed after a successful Venus mission), the international ISEE-3 (ICE) spacecraft and the European Space Agency's Giotto. NASA's Pioneer 7 and Pioneer 12 also contributed the the bounty of science data collected.Tapestry on men looking at comet.A panel from the Bayeux tapestry showing people looking at a what would later be known as Halley's comet. Credit: By Myrabella - Own work, Public DomainHalley's Connection to Meteor ShowersEach time that Halley returns to the inner solar system its nucleus sprays ice and rock into space. This debris stream results in two weak meteor showers each year: the Eta Aquarids in May and the Orionids in October.SizeHalley's dimensions are about 9.3 by 5 miles (15 kilometers by 8 kilometers). It is one of the darkest, or least reflective, objects in the solar system. It has an albedo of 0.03, which means that it reflects only three percent of the light that falls on it.OrbitComet Halley moves backward (opposite to Earth's motion) around the Sun in a plane tilted 18 degrees to that of the Earth's orbit. Halley's backward, or retrograde, motion is unusual among short-period comets, as is its greatest distance from the Sun (aphelion) is beyond the orbit of Neptune.Halley's orbit period is, on average, 76 Earth years. This corresponds to an orbital circumference around the Sun of about 7.6 billion miles (12.2 billion kilometers). The period varies from appearance to appearance because of the gravitational effects of the planets. Measured from one perihelion passage to the next, Halley's period has been as short as 74.42 years (1835-1910) and as long as 79.25 years (451-530).