Neptune is the eighth and farthest planet from the Sun in the Solar System.Neptune is 17 times the mass of Earth.
Neptune is similar in composition to Uranus, and both have compositions which differ from those of the larger gas giants, Jupiter and Saturn.
Neptune's atmosphere is composed primarily of hydrogen and helium, along with traces of hydrocarbons and possibly nitrogen.
Astronomers sometimes categorise Uranus and Neptune as "ice giants".
Neptune's atmosphere is 80% hydrogen and 19% helium. A trace amount of methane is also present.
Neptune's atmosphere is sub-divided into two main regions; the lower troposphere, where temperature decreases with altitude, and the stratosphere, where temperature increases with altitude.
Neptune has a planetary ring system, though one much less substantial than that of Saturn.