Neptune

Neptune is the eighth and farthest planet from the Sun in the Solar System.

It is an "ice giant".

It is the fourth-largest planet by diameter and the third-largest by mass.

Among the gaseous planets in the Solar System, Neptune is the most dense.

Neptune is 17 times the mass of Earth.

Neptune was the first and only planet found by mathematical prediction rather than by empirical observation.

Orbital period

164.8 solar years.

Etymology

Named after the Roman god of the sea.

Appearance

Traces of methane in the outermost regions in part account for the planet's blue appearance.

Atmosphere

Because of its great distance from the Sun, Neptune's outer atmosphere is one of the coldest places in the Solar System, with temperatures at its cloud tops approaching 55 K (−218 °C).

Moons

Neptune has 14 known moons.

1. Triton is the largest Neptunian moon, comprising more than 99.5% of the mass in orbit around Neptune, and it is the only one massive enough to be spheroidal.
2. Nereid
3. Proteus