Halley's Comet travels through the solar system in a highly elliptical orbit, looping around the Sun at one end, which is where we see it from Earth, and Neptune at the other. Observing the comet in 1682 and studying records of previous sightings, the English astronomer and mathematician Edmond Halley (1656-1742) calculated that the comet took about 76 years to complete an orbit, and successfully predicted its return in 1758. This photograph was taken from Arequipa, Peru, using a 30-minute exposure on blue-sensitive film.