Halley's comet comes close to Earth about every 76 years. It was most recently seen in 1985 and 1986 and is predicted to appear again in 2061. Every appearance of what is now known as Comet Halley has been recorded by astronomers (scientists specializing in the study of matter in outer space) since the year 239 B.C.
The comet is named for famed English astronomer Edmund Halley (1656-1742). In 1682, Halley observed a bright comet and noted that it was moving along an orbit similar to comets that had been noted in 1531 and 1607. He concluded that the three comets were actually one, and that the comet completed an orbit around the sun once every 76 years.
In 1705, Halley published A Synopsis of the Astronomy of Comets in which he predicted that this comet would return in 1758. On Christmas night, 1758, a German farmer and amateur astronomer named Johann Palitzsch spotted the comet in the precise area of the sky that Halley had foretold.
Prior to Halley's study of comets, no one knew where comets came from or what paths they followed. Comets were often thought to be evil omens or signs of impending disaster. Halley proved that they are natural objects subject to the laws of gravity.
Sources: Moore, Patrick. International Encyclopedia of Astronomy, p. 177; Sagan, Carl, and Ann Druyan. Comet, p. 364.