By 1705, Edmond Halley had determined that comets orbit the sun on long, elliptic paths. Furthermore, he noted that comets appearing in the years 1531, 1607, and 1682 had similar trajectories and were separated by regular intervals of about 75 years. Halley correctly suggested that each of these sightings was of the same orbiting comet, later named Halley’s Comet.

Close-up images of Halley’s Comet taken by the Giotto spacecraft in 1986 show jets of gas and dust emanating from the comet. These emissions make up the bright comet head and tail seen from the earth.

4. Halley’s Comet in 1985

5. Halley’s Comet in 1910

6. Jets of gas and dust emanating from Halley’s Comet