In its long space journey, Halley's comet begins its return to Earth.
On Saturday, December 9, Halley's comet reached the furthest point of its orbit around the Sun, about 35 astronomical units, placing it well beyond Neptune's orbit and almost at the level of Pluto's orbit. This point marks the halfway point of its 76-year orbital cycle around our star.
Artist's impression of the Giotto probe.
The last time Halley's comet passed close to the Sun was on February 9, 1986. On that occasion, it approached the Sun to about 54.5 million miles (87.8 million kilometers), slightly less than the distance that separates the Sun from Venus. Since 2003, astronomers have lost sight of the comet, it becoming too small and too faint to be observed.
Comets, celestial bodies made of ice and dust, are famous for their spectacular tails. These tails form when solar radiation vaporizes the ice in the comet's body, leading to a trail of gas and dust.
Edmond Halley, the astronomer who named the comet, was the first to predict its return to Earth's skies. Observing the comet in 1682, he initially described it as a "hairy star" without understanding its exact nature. By comparing his observations with similar appearances in 1531 and 1607, he postulated that it was the same object. Edmond Halley predicted its return in 1758. His prediction came true, but he was not present to see it, having died in 1742.
This view of the nucleus of Halley's comet was obtained by the Giotto probe during its passage 372 miles (600 kilometers) from the comet's nucleus on March 13, 1986.
Image credit: ESA/MPAe Lindau
Until its next passage near the Sun on July 28, 2061, Halley's comet will continue to light up our sky through two annual meteor showers. The icy debris it left during its previous travels through Earth's orbit gives rise to the Delta Aquarids meteor shower in May and the Orionids in October, transforming these debris into shooting stars.