Ten fun facts about Neptune

Fact 1
It is the fourth-largest planet according to diameter and the third-largest according mass.

Fact 2
Among the gaseous planets in our solar system, Neptune is the most dense.

Fact 3
Neptune is 17 times the Earth’s mass.

Fact 4
Neptune's atmosphere, while very much like Jupiter’s and Saturn’s in that it is primarily composed of hydrogen and helium, along with traces of hydrocarbons as well as possibly nitrogen, contains a higher proportion of “ices” such as water, ammonia, and also methane.

Fact 5
Named after the Roman god of the sea, the planet’s astronomical symbol is a stylized version of the god Neptune's trident.

Fact 6
Astronomers sometimes regard Uranus and Neptune as “ice giants” in order to emphasize these distinctions.

Fact 7
Traces of methane in the outermost regions in part account for Neptune’s blue appearance.

Fact 8
Because of its great distance from the Sun, Neptune's outer atmosphere is one of the coldest places in the Solar System.

Fact 9
Neptune is similar in composition to Uranus, and both have compositions which differ from those of the larger gas giants, Jupiter, and Saturn.

Fact 10
Neptune has been visited by one spacecraft, Voyager 2, which flew by the planet on Aug. 25, 1989.