Schematic diagram showing the path of Halley's Comet as it rounds the Sun, together with the orbits (blue) of Jupiter, Saturn, Uranus and Neptune. Comet Halley describes a highly elliptical orbit which takes it out beyond Neptune but not as far as Pluto. Its orbit is inclined 18 degrees below the plane in which the planets orbit the Sun. It returns to the centre of the solar system every 76 years, most recently in 1985/86.