Neptune has an average diameter of 30,598 miles, which is approximately almost four times Earth's diameter. In terms of mass, Neptune weighs approximately 102 trillion trillion kilograms, making it 17 times heavier than Earth.
Neptune has a surface area of approximately 2.9 billion square miles, which is nearly 15 times larger than Earth's surface area. Neptune was discovered on Sept. 23, 1846, after Johann Gottfried Galle observed it at the Berlin Observatory following orbit predictions made by French mathematician Urbain Joseph Le Verrier. A single orbit around the sun takes Neptune approximately 164.79 Earth years at an average velocity of 12,158 miles per hour.