Edmund Halley, (1656-1742). English astronomer. Halley’s first important work was a star catalogue of the Southern Hemisphere. In 1684 he met Newton and encouraged him to write Principia, a study of the laws of planetary motion. Halley also produced the first meteorological map of the world and the first magnetic chart. In 1705 he published A Synopsis of the Astronomy of Comets, in which he accurately predicted the return of a comet previously seen in 1531, 1607, and 1682. The comet, now known as Halley’s Comet, last appeared in 1986.