Neptune is 17 times the mass of the Earth. It is the densest planet it the solar system. Neptune is at a distance of 4.495 billion kilometers from the Sun. It has a radius of 24,622 kilometers from its core. 1 year here is equal to 165 years on Earth! Which means right now, at this moment, 165 years ago, Neptune was at the very same spot! It has a surface area of 7.618 billion km2 ! Its near-twin is Uranus.