ice giant
Neptune
The stormy outer giant
Neptune is the eighth and most distant planet from the Sun. Its striking blue color comes from methane in its atmosphere, and it hosts powerful storms with winds that can reach supersonic speeds.
Key facts
- Diameter
- 49,244 km
- Radius
- 24,622 km
- Mass
- 1.024e+26 kg
- Gravity (Earth = 1)
- 1.120
- Density
- 1.638 g/cm³
- Distance from Sun
- 4,495,000,000 km
- Orbital period
- 59,800 Earth days
- Rotation period
- 16.11 hours
- Average temperature
- -200°C
- Known moons
- 16
Values are approximate and based on cited sources.
Atmosphere
- Hydrogen
- Helium
- Methane
Surface
No solid surface; deep clouds and storms sit above a fluid interior.
Internal structure
A rocky core, a mantle of water, ammonia, and methane ices, and a hydrogen-helium atmosphere.
Moons
Triton
Its retrograde orbit suggests it was captured from the Kuiper Belt.
Exploration missions
- • Voyager 2
Sources
- NASA Science — Neptune— last verified 2026-01-15