neptune is a kind of planet in the solar system & planets in the solar system orbit the sun ->  neptune orbits the sun in the solar system  neptune orbits the sun in the solar system & furthest / farthest means greatest / most / highest in distance & neptune is the planet that is furthest to the sun in the solar system ->  the distance between neptune and the sun it orbits is the greatest in the solar system  the distance between neptune and the sun it orbits is the greatest in the solar system & as the distance of a planet from the star it orbits increases , the length of a planetary year on that planet will increase -> neptune has the longest solar year / planetary year in the solar system