Neptune #72 Neptune is the eighth and farthest-known Solar planet from the Sun. In the Solar System, it is the fourth-largest planet by diameter, the third-most-massive planet, and the densest giant planet. It is 17 times the mass of Earth, slightly more massive than its near-twin Uranus.  Properties: Galaxy: Milky Way System: Solar Main Planet: Sun Type: Planet Name: Neptune Resource: Tantalum Rarity: Mythical