Ice giant
Neptune
The blue world
Neptune is the eighth and most distant planet from the Sun, an ice giant so far away that sunlight takes over four hours to reach it. It was the first planet located through mathematical prediction rather than observation, found in 1846 exactly where calculations said it would be. Neptune has the strongest winds in the solar system, with gusts measured beyond 2,000 km/h, and its deep blue color comes from methane in its atmosphere.
Quick facts
- Distance from Sun
- 4.5 billion km (30.1 AU)
- Diameter
- 49,244 km (3.9x Earth)
- Day length
- 16.1 hours
- Year length
- 165 Earth years
- Moons
- 16 confirmed
- Avg. temperature
- -200 C
What's it like there?
Neptune is a dark, cold, extraordinarily windy world. Supersonic winds whip clouds of frozen methane across the planet faster than the speed of sound on Earth. It receives about 900 times less sunlight than Earth, so high noon on Neptune resembles dim twilight. Like Uranus, its interior is a hot dense fluid of water, methane, and ammonia. Its largest moon, Triton, orbits backwards and vents nitrogen geysers.
Notable moons
Triton
Orbits backwards, is geologically active, and is likely a captured Kuiper Belt object.
Fun facts
Neptune was discovered by math: its position was predicted before it was seen.
Winds on Neptune can exceed 2,000 km/h, the fastest known.
One Neptune year lasts 165 Earth years; it completed its first observed orbit in 2011.
Its moon Triton is one of the coldest known objects in the solar system (-235 C).
Neptune radiates more than twice the energy it receives from the Sun.
Exploration history
Voyager 2 1989
The only spacecraft to have visited Neptune, discovering its Great Dark Spot and six moons.
Neptune vs Earth
| Property | Earth | Neptune |
|---|---|---|
| Diameter | 12,742 km | 49,244 km |
| Year length | 365 days | 165 years |
| Moons | 1 | 16 |
| Average temperature | 15 C | -200 C |
| Sunlight received | 1x | ~1/900th of Earth |
Scientific Sources & Provenance
All data is verified against official space agency records (NASA, ESA, and IAU).
- NASA Science / Mission Datahttps://science.nasa.gov/neptune/
- NASA Science / Mission Datahttps://nssdc.gsfc.nasa.gov/planetary/factsheet/neptunefact.html