Neptune is the eighth and farthest planet from the Sun in

Last updated: 8/30/2023

Neptune is the eighth and farthest planet from the Sun in the Solar System It is the fourt largest planet by diameter and the third largest by mass Neptune is 17 times the mass Earth and is somewhat more massive than its near twin Uranus which is 15 times the mas of Earth but not as dense On average Neptune orbits the Sun at a distance of 30 1 AL approximately 30 times the Earth Sun distance Named for the Roman god of the sea its astronomical symbol is a stylized version of the god Neptune s trident Neptune was the first planet found by mathematical prediction rather than by empirical observation Unexpected changes in the orbit of Uranus led Alexis Bouvard to deduce that its orbit was subject to gravitational perturbation by an unknown planet Neptune was subsequently observed on September 23 1846 by Johann Galle within a degree of the position predicted by Urbain Le Verrier and its largest moon Triton was discovered shortly thereafter though none of the planet s remaining 12 moons were located telescopically until the 20th century Neptune has been visited by only one spacecraft Voyager 2 which flew by the planet on August 25 1989 O Uranus Neptune Earth Sun distance